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methadone hydrochloride
Classes
Agents for Opioid Dependence
Agents for Opioid Withdrawal
Opioid Agonists
Administration
When given as part of a methadone maintenance program, methadone may only be administered in an oral form and according to the requirements outlined in the Narcotic Addict Treatment Act (NATA) [21USC 823(g)].
Monitor patients closely for respiratory depression, especially within the first 24 to 72 hours of therapy initiation or dose escalation.
Storage: Store methadone securely in a location not accessible by others.
Disposal: Flush unused methadone down the toilet when it is no longer needed if a drug take-back option is not readily available.[33136]
Dispersible tablets (Diskets)
Do not chew or swallow the tablets before dispersing in liquid. Disperse the desired dose of tablets in approximately 120 mL of water, orange juice, or other acidic fruit beverages before administration.
Insoluble excipients will be present after tablets are dissolved; they will not completely dissolve. If residue remains in cup after initial administration, add a small amount of liquid and administer the resulting admixture to the patient.[51313]
Oral solution
Carefully check dose before administering medication as multiple concentrations of methadone oral solution are available, including a concentrated version.[31280]
Measure dosage using a calibrated measuring device.
Visually inspect parenteral products for particulate matter and discoloration prior to administration whenever solution and container permit.
Intravenous methadone is typically administered intermittently; however, methadone has also been administered intravenously for patient-controlled analgesia (PCA) via a rate controlled device as a bolus dose and as a continuous infusion.[31283]
Inject into a large muscle mass.
The absorption of intramuscular (IM) methadone has not been well characterized and appears to be unpredictable.
Local tissue reactions may occur with IM use.[51312]
Inject subcutaneously taking care not to inject intradermally.
The absorption of subcutaneous methadone has not been well characterized and appears to be unpredictable.
Local tissue reactions may occur with subcutaneous use.[51312]
Adverse Reactions
pulmonary edema / Early / Incidence not known
respiratory arrest / Rapid / Incidence not known
apnea / Delayed / Incidence not known
seizures / Delayed / Incidence not known
oliguria / Early / Incidence not known
anaphylactoid reactions / Rapid / Incidence not known
SIADH / Delayed / Incidence not known
ventricular fibrillation / Early / Incidence not known
cardiomyopathy / Delayed / Incidence not known
bradycardia / Rapid / Incidence not known
ventricular tachycardia / Early / Incidence not known
cardiac arrest / Early / Incidence not known
heart failure / Delayed / Incidence not known
torsade de pointes / Rapid / Incidence not known
neonatal opioid withdrawal syndrome / Delayed / Incidence not known
bone fractures / Delayed / Incidence not known
serotonin syndrome / Delayed / Incidence not known
pancreatitis / Delayed / Incidence not known
biliary obstruction / Delayed / Incidence not known
psychological dependence / Delayed / 10.0
tolerance / Delayed / Incidence not known
hypoventilation / Rapid / Incidence not known
respiratory depression / Rapid / Incidence not known
dyspnea / Early / Incidence not known
hypoxia / Early / Incidence not known
nystagmus / Delayed / Incidence not known
dysphoria / Early / Incidence not known
euphoria / Early / Incidence not known
confusion / Early / Incidence not known
hallucinations / Early / Incidence not known
glossitis / Early / Incidence not known
constipation / Delayed / Incidence not known
blurred vision / Early / Incidence not known
urinary retention / Early / Incidence not known
phlebitis / Rapid / Incidence not known
edema / Delayed / Incidence not known
hypomagnesemia / Delayed / Incidence not known
hypokalemia / Delayed / Incidence not known
hypoglycemia / Early / Incidence not known
impotence (erectile dysfunction) / Delayed / Incidence not known
infertility / Delayed / Incidence not known
hyponatremia / Delayed / Incidence not known
adrenocortical insufficiency / Delayed / Incidence not known
hypotension / Rapid / Incidence not known
ST-T wave changes / Rapid / Incidence not known
hypertension / Early / Incidence not known
sinus tachycardia / Rapid / Incidence not known
palpitations / Early / Incidence not known
orthostatic hypotension / Delayed / Incidence not known
peripheral vasodilation / Rapid / Incidence not known
QT prolongation / Rapid / Incidence not known
physiological dependence / Delayed / Incidence not known
withdrawal / Early / Incidence not known
hyperthyroidism / Delayed / Incidence not known
thrombocytosis / Delayed / Incidence not known
osteoporosis / Delayed / Incidence not known
hyperamylasemia / Delayed / Incidence not known
thrombocytopenia / Delayed / Incidence not known
hyperalgesia / Delayed / Incidence not known
insomnia / Early / Incidence not known
agitation / Early / Incidence not known
drowsiness / Early / Incidence not known
flushing / Rapid / Incidence not known
dizziness / Early / Incidence not known
restlessness / Early / Incidence not known
asthenia / Delayed / Incidence not known
headache / Early / Incidence not known
anxiety / Delayed / Incidence not known
anorexia / Delayed / Incidence not known
vomiting / Early / Incidence not known
nausea / Early / Incidence not known
abdominal pain / Early / Incidence not known
miosis / Early / Incidence not known
xerostomia / Early / Incidence not known
urticaria / Rapid / Incidence not known
rash / Early / Incidence not known
injection site reaction / Rapid / Incidence not known
pruritus / Rapid / Incidence not known
amenorrhea / Delayed / Incidence not known
weight gain / Delayed / Incidence not known
libido decrease / Delayed / Incidence not known
gonadal suppression / Delayed / Incidence not known
diaphoresis / Early / Incidence not known
syncope / Early / Incidence not known
Boxed Warning
Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP). Although the risk of QT prolongation appears to be dose-related , with most incidences of QT prolongation and torsade de pointes occurring in patients receiving large doses for pain management (i.e. > 100 mg/day), it is important to note that smaller doses for maintenance of opiate addiction have also been implicated. A public health advisory was issued concerning cardiac-related deaths, which have been reported during initiation of methadone treatment as well as during conversion to methadone from other opiates. Extreme caution is recommended during initiation of treatment, conversion from one opiate to another, and dose titrations. An understanding of methadone pharmacokinetic parameters is critical. In addition to slowing the rate of cardiac repolarization thus lengthening the QT interval, methadone may produce cholinergic side effects (by stimulating medullary vagal nuclei) causing bradycardia and induce the release of histamine causing peripheral vasodilation. Use methadone with extreme caution, if at all, in patients whose ability to maintain blood pressure has already been compromised by hypovolemia or administration of certain CNS depressant medications such as phenothiazines or general anesthetics. Monitor patients for hypotension at the initiation of therapy and during dose titration. These effects can cause problems in patients with cardiac disease (e.g., angina, heart failure). Methadone should be used cautiously in patients with cardiac arrhythmias, hypokalemia, hypomagnesemia, hypotension, hypovolemia, or orthostatic hypotension. Opiate agonists can induce vasovagal syncope or orthostatic hypotension. A risk/benefit evaluation of methadone and consideration of alternative therapy is prudent for patients with QT prolongation (congenital long QT syndrome or acquired QT prolongation syndromes), patients with a history of torsade de pointes, patients with unexplained syncope, and those with multiple risk factors for QT prolongation including family history and/or coadministration of contributing medications (i.e. drugs associated with QT prolongation and drugs that inhibit the cytochrome P450 enzymes). Use methadone with caution in patients with cardiac disease or other conditions that may increase the risk of QT prolongation including heart failure, bradycardia, myocardial infarction, hypertension, coronary artery disease, hypocalcemia, or in patients receiving medications known to cause electrolyte imbalances. Females, elderly patients, patients with diabetes mellitus, thyroid disease, malnutrition, a history of alcohol abuse, or hepatic impairment may also be at increased risk for QT prolongation. A 2009 clinical guideline for cardiac safety with methadone treatment recommends that prescribers: (1.) discuss the risk of arrhythmia with patients; (2.) take a complete cardiac clinical history; (3.) screen patients for QT prolongation with ECG monitoring prior to initiation of methadone, at 3 months, and annually thereafter; (4.) use the ECG findings to stratify patient risk (i.e., patients with a QTc interval of 451—499 ms should receive more frequent monitoring and discuss the potential risks vs. benefits of treatment, patients with a QTc interval of >= 500 ms should receive intervention to lower cardiac risk either by discontinuing or lowering the methadone dose or by eliminating contributing factors); and (5.) be aware of methadone-drug interactions. Drugs known to prolong the QT interval, potentiate hypokalemia, or reduce methadone elimination should be coadministered with a careful assessment of risks versus benefits.
Opioid use requires an experienced clinician who is knowledgeable about the use of opioids, including the use of extended-release/long-acting opioids, and how to mitigate the associated risks. Opioids expose users to the risks of addiction, abuse, and misuse, which can occur at any dosage or duration. Although the risk of addiction in any individual is unknown, it can occur in persons appropriately prescribed opioids. Addiction can occur at recommended dosages and if the drug is misused or abused. Assess each individual's risk for opioid addiction, abuse, or misuse before prescribing an opioid, and monitor for the development of these behaviors or conditions. Risks are increased in persons with a personal or family history of substance abuse (including alcoholism) or mental illness (e.g., major depression). The potential for these risks should not prevent the proper management of pain in any given individual. Persons at increased risk may be prescribed opioids, but use in such persons necessitates intensive counseling about the risks and proper use of the opioid along with intensive monitoring for signs of addiction, abuse, and misuse. Abuse and addiction are separate and distinct from physical dependence and tolerance; persons with addiction may not exhibit tolerance and symptoms of physical dependence. Opioids are sought by drug abusers and persons with addiction disorders and are subject to criminal diversion. Abuse of opioids has the potential for overdose or poisoning and death. Consider these risks when prescribing or dispensing an opioid. Strategies to reduce these risks include prescribing the drug in the smallest appropriate quantity. Abuse or misuse of methadone tablets by cutting, breaking, chewing, crushing, snorting, or injecting the dissolved product will result in the uncontrolled delivery of methadone and can result in overdose and death. Dosing errors may result from confusion between mg and mL when prescribing, dispensing, and administering methadone oral solution. Ensure that the dose is communicated clearly and dispensed accurately. Instruct patients on how to measure the dose and to use a calibrated oral dosing device. Keep opioids out of the reach of pediatric persons, others for whom the drug was not prescribed, and pets as accidental exposure or improper use may cause respiratory failure and a fatal overdose. Accidental exposure of even a single dose of an opioid, especially by younger persons, can result in a fatal overdose. Because the risk of overdose increases as opioid dose increases, reserve titration to higher doses of an opioid for persons in whom lower doses are insufficiently effective and in whom the expected benefits of using a higher dose opioid clearly outweigh the substantial risks. Long-acting opioids are not intended for use in the management of acute pain or on an as-needed basis but rather only for the management of severe and persistent pain that requires an extended treatment period with a daily opioid and for which alternative treatment options are inadequate. Discuss the availability of naloxone with all patients and consider prescribing it in persons who are at increased risk of opioid overdose, such as those who are also using other CNS depressants, who have a history of opioid use disorder (OUD), who have experienced a previous opioid overdose, or who have household members or other close contacts at risk for accidental exposure or opioid overdose.
Methadone is contraindicated in persons with significant respiratory depression and those with acute or severe asthma in an unmonitored setting or in the absence of resuscitative equipment. Avoid coadministration with other CNS depressants when possible, as this significantly increases the risk for profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing of these drugs for use in persons for whom alternative treatment options are inadequate; if concurrent use is necessary, use the lowest effective dosages and minimum treatment durations needed. Monitor closely for signs or symptoms of respiratory depression and sedation. Persons with chronic obstructive pulmonary disease (COPD), cor pulmonale, respiratory insufficiency, hypoxemia, hypercapnia, or preexisting respiratory depression are at increased risk of decreased respiratory drive even at recommended doses. Persons with advanced age, cachexia, or debilitation are also at an increased risk for opioid-induced respiratory depression. Monitor such persons closely, particularly when initiating and titrating the opioid; consider the use of non-opioid analgesics. Opioids increase the risk of central sleep apnea (CSA) and sleep-related hypoxemia in a dose-dependent fashion. Consider decreasing the opioid dosage in persons with CSA. Respiratory depression, if left untreated, may cause respiratory arrest and death. Carbon dioxide retention from respiratory depression may also worsen opioid sedating effects. Careful monitoring and dose titration is required, particularly when CYP2B6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 inhibitors are used concomitantly. Concomitant use or discontinuation of CYP2B6, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 inhibitors may result in an increase in plasma methadone concentrations and potentiate the risk of fatal respiratory depression. Management of respiratory depression may include observation, necessary supportive measures, and opioid antagonist use when indicated.
There are no adequate and well-controlled studies with methadone in pregnant women. Use methadone for severe pain during pregnancy only if the potential benefit justifies the potential risk to the fetus. Medical withdrawal of pregnant, opioid-dependent women from methadone is not recommended. When methadone is used during pregnancy as part of a supervised, therapeutic regimen, it is unlikely to pose substantial teratogenic risk. Pregnant women in methadone maintenance programs may have reduced incidence of obstetric and fetal complications and neonatal morbidity and mortality when compared to women using illicit drugs. Untreated opioid addiction in pregnancy is associated with adverse obstetrical outcomes and risk of continued or relapsing illicit opioid use. Consider these risks in pregnant women treated with methadone for maintenance treatment of opioid addiction. No increased risk of miscarriage in the second trimester or premature delivery in the third trimester was noted by a retrospective review of data from 101 opioid-dependent women. Benefits of methadone therapy during pregnancy include assisting women staying free of heroin or other opioids, increasing prenatal care, lessening the possibility of fetal death, and reducing the risk of HIV and hepatitis infection. Infants born to narcotic-addicted women treated with methadone during pregnancy have been found to have decreased fetal growth with reduced birth weight, length, or head circumference. The growth deficit does not appear to persist into later childhood. Children born to mothers who received methadone during pregnancy demonstrate mild but persistent performance deficits on psychometric and behavioral tests and may have an increased risk of visual development anomalies. Administration of methadone to pregnant animals during organogenesis through lactation resulted in decreased litter size, increased pup mortality, decreased pup body weights, developmental delays, and long-term neurochemical changes in the brain which correlate with altered behavioral responses at exposures comparable to and less than the human daily dose of 120 mg. Methadone clearance may be increased during pregnancy. The methadone dose or interval may need to be increased as the pregnancy progresses due to changes in plasma volume and renal blood flow; due to an increased metabolism of methadone during pregnancy, close monitoring of pregnant women is recommended. Methadone is not recommended for analgesia during labor and obstetric delivery due to its long duration of action and potential for respiratory depression in the newborn. Women maintained on methadone require appropriate obstetric pain management, as methadone maintenance does not provide analgesia. Narcotics with mixed agonist/antagonist properties should not be used for pain control during labor in patients chronically treated with methadone as they may precipitate acute withdrawal. Prolonged maternal use of opioids, such as methadone, during pregnancy may result in neonatal opioid withdrawal syndrome (NOWS). This syndrome can be life-threatening. Severe symptoms may require pharmacologic therapy managed by clinicians familiar with neonatal opioid withdrawal. Monitor the neonate for withdrawal symptoms including irritability, hyperactivity, abnormal sleep pattern, high-pitched crying, tremor, vomiting, diarrhea, and failure to gain weight. Onset, duration, and severity of opioid withdrawal may vary based on the specific opioid used, duration of use, timing and amount of last maternal use, and rate of elimination by the newborn.
Common Brand Names
Dolophine, Methadose
Dea Class
Rx, schedule II
Description
A phenylheptylamine synthetic opiate agonist; is structurally unrelated to morphine
Used in medically supervised opiate withdrawal and maintenance programs; effective for the relief of severe or chronic pain
For the treatment of opiate dependence, prescriber must register and comply with the Narcotic Addict Treatment Act (NATA) [21USC 823(g)]
Dosage And Indications
NOTE: Persons need to show withdrawal symptoms but no signs of sedation or intoxication.
NOTE: Methadone when used for the treatment of opioid dependence in detoxification or maintenance programs, shall be dispensed only by opioid treatment programs (and agencies, practitioners or institutions by formal agreement with the program sponsor) certified by the Substance Abuse and Mental Health Services Administration and approved by the designated state authority.
NOTE: Consider loss of opioid tolerance for any person who has not taken opioids for more than 5 days.
For the treatment of iatrogenic opioid agonist dependence in pediatric patients†. Oral dosage Infants†, Children†, and Adolescents†
0.05 to 0.1 mg/kg PO every 6 hours, initially. Titrate dose by 0.05 mg/kg/dose until symptoms are controlled. Once symptoms are controlled, taper dosage incrementally (10% to 20% of initial dose every 1 to 2 days), lengthening interval (e.g., every 12 to 24 hours) prior to discontinuation; most patients can be tapered to off within 10 days. Dosage, interval, length of treatment, and taper schedule must be individualized based on patient's previous opioid dose and symptoms of withdrawal. Various dosing regimens have been reported and some practitioners suggest the daily dosage of opioid infusion (e.g., fentanyl) be converted to an equipotent daily dosage of methadone, however this may lead to unnecessarily high doses.
0.05 to 0.1 mg/kg PO every 6 hours, initially. Titrate dose by 0.05 mg/kg/dose until symptoms are controlled. Once symptoms are controlled, taper dosage incrementally (10% to 20% of initial dose every 1 to 2 days), lengthening interval (e.g., every 12 to 24 hours) prior to discontinuation; most patients can be tapered to off within 10 days. Dosage, interval, length of treatment, and taper schedule must be individualized based on patient's previous opioid dose and symptoms of withdrawal. Various dosing regimens have been reported and some practitioners suggest the daily dosage of opioid infusion (e.g., fentanyl) be converted to an equipotent daily dosage of methadone, however this may lead to unnecessarily high doses.
20 to 30 mg PO once, initially; may administer an additional 5 to 10 mg after 2 to 4 hours if withdrawal symptoms have not been suppressed or if symptoms reappear, up to 40 mg/day on day 1. Use lower initial doses for persons whose tolerance is expected to be low at treatment entry. Adjust the dose over the first week of treatment based on control of withdrawal symptoms at the time of expected peak activity (e.g., 2 to 4 hours after dosing). Subsequently, titrate dose to a level that prevents opioid withdrawal symptoms for 24 hours, reduces drug hunger or craving, and blocks or attenuates the euphoric effects of self-administered opioids, ensuring tolerance to sedative effects. Usual dose range: 80 to 120 mg/day. Continue as long as desired and continued benefit is derived. During medically supervised withdrawal from methadone treatment, decrease dose by 10% every 10 to 14 days.
NOTE: Injectable methadone is not FDA-approved for the outpatient treatment of opioid dependence; parenteral methadone is to be used only for persons unable to take oral medication, such as hospitalized patients.
Convert the total daily oral methadone dose to an equivalent parenteral dose using a 2:1 dose ratio (e.g., 10 mg oral methadone to 5 mg parenteral methadone).
Up to 40 mg/day in divided doses to achieve an adequate stabilizing level. After 2 to 3 days, decrease dose by 20% every 1 to 2 days in hospitalized persons as tolerated; ambulatory persons may need a slower taper.
NOTE: Methadone tablets or oral solution should be reserved for patients in whom alternative treatment options (e.g., non-opioid analgesics or immediate-release opioids) are ineffective, not tolerated, or would otherwise provide inadequate pain management. Discontinue all other around-the-clock opioid drugs upon initiation of methadone.
Oral dosage Adults
Initially, 2.5 mg PO every 8 to 12 hours in the opioid-naive patient; titrate to pain relief. For the relief of severe, chronic pain in opioid-tolerant patients, convert the current total daily dose of all opioids to an oral morphine equivalent dose, then multiply the morphine equivalent dose by the corresponding percentage in the dose conversion table provided in the FDA-approved labeling. Divide the total daily methadone dose into an appropriate daily regimen. Clinical guidelines suggest that methadone should be initiated at a dose that is 75% to 90% lower than the calculated equianalgesic dose and no higher than 30 to 40 mg/day in patients with opioid tolerance. If patients experience breakthrough pain, dose adjustment or a small rescue dose of an immediate-release analgesic should be considered. Use extreme caution to avoid overdosage; it is safer to underestimate a patient's daily oral methadone requirement. Due to the potential for delayed toxic effects (e.g., respiratory depression), clinical guidelines recommend dose titration every 5 to 7 days , although the manufacturer suggests adjustments may be made every 3 to 5 days. Titrate the dosage by no more than 5 mg/day in patients on relatively low doses of other opioids prior to methadone treatment (less than 40 to 60 mg/day of oral morphine equivalent) and by no more than 10 mg/day in patients taking higher doses of morphine equivalent. Patients previously prescribed methadone who have not taken opioids for 1 to 2 weeks should be considered opioid-naive for the purposes of methadone reinitiation. Monitor patients closely for respiratory depression, especially during the first 24 to 72 hours after initiation or dosage increase. When the patient no longer requires methadone, taper the dose gradually every 2 to 4 days to prevent withdrawal in the physically-dependent patient.
2.5 to 10 mg IV, IM, or subcutaneously every 8 to 12 hours, as needed for opioid-naive patients. In opioid-tolerant patients, convert the current total daily dose of all opioids to an oral morphine equivalent dose, then multiply the morphine equivalent dose by the corresponding percentages in the dose conversion table provided in the FDA-approved labeling. FDA-approved labeling recommends an initial 2:1 dose ratio to convert from oral to parenteral methadone. Clinical guidelines suggest that methadone should be initiated at a dose that is 75% to 90% lower than the calculated equianalgesic dose. Use extreme caution to avoid overdosage; it is safer to underestimate a patient's daily oral methadone requirement. Due to the potential for delayed toxic effects (e.g., respiratory depression), clinical guidelines recommend dose titration every 5 to 7 days, although the manufacturer suggests adjustments may be made every 3 to 5 days. When the patient no longer requires methadone, taper the dose gradually every 2 to 4 days to prevent withdrawal in the physically-dependent patient.
0.1 to 0.3 mg/kg/dose PO every 8 hours, initially, based on Finnegan Score. In a randomized, controlled trial, patients treated with methadone had better short-term outcomes such as decreased length of hospital stay, length of stay attributable to NAS, and length of drug treatment compared to those receiving morphine. 0.05 to 0.1 mg/kg/dose PO every 6 to 24 hours, initially, has also been reported. Titrate by 0.025 to 0.05 mg/kg/dose until symptoms are controlled. Once symptoms are controlled, taper dosage incrementally (10% to 20% of initial dose every 12 to 48 hours), lengthening interval (e.g., every 12 to 24 hours instead of every 6 hours) prior to discontinuation. Dosage, interval, length of treatment, and taper schedule are variable and must be individualized to control symptoms of withdrawal. Weaning may take several weeks to months. Monitor patients frequently for respiratory depression, particularly during the first 24 to 72 hours after initiation or dose escalation.
2.5 to 5 mg/day PO once daily or in divided doses, initially. Titrate based on efficacy and adverse effects. Usual dose: 5 to 20 mg/day. Longer-acting and controlled-release drugs are preferred, especially at night.
†Indicates off-label use
Dosing Considerations
Start these patients on lower doses and titrate slowly while carefully monitoring for signs of respiratory and CNS depression. Adjust dosage based upon clinical response; no specific quantitative recommendations are available.
Renal ImpairmentAdults:
Dosage adjustments may be necessary in adult patients with renal impairment; guide adjustments based on clinical response. Methadone has not been extensively evaluated in patients with renal insufficiency. Since unmetabolized methadone and its metabolites are excreted in urine to a variable degree, start these patients on lower doses and with longer dosing intervals and titrate slowly while carefully monitoring for signs of respiratory and CNS depression. For example, for CrCl less than 10 mL/minute, one source recommends that the adult initial dose be reduced by 50 to 75%.
Pediatrics:
Methadone has not been extensively evaluated in patients with renal insufficiency. Since unmetabolized methadone and its metabolites are excreted in urine to a variable degree, start these patients on lower doses and with longer dosing intervals and titrate slowly while carefully monitoring for signs of respiratory and CNS depression.
The following initial interval adjustments have been recommended for pediatric patients (normal interval every 4 to 12 hours):
CrCl 30 to 50 mL/minute: Administer dosage every 6 to 8 hours.
CrCl 10 to 30 mL/minute: Administer dosage every 8 to 12 hours.
CrCl less than 10 mL/minute: Administer dosage every 12 to 24 hours.
Drug Interactions
Abacavir: (Moderate) In a study of 11 adult HIV-infected subjects receiving methadone maintenance therapy (40 to 90 mg/day) and abacavir 600 mg twice daily (twice the current recommended dose), methadone clearance increased by 22% (6% to 42%). While this interaction will not require dosage adjustment in the majority of patients, a small number of patients may require increased doses of methadone. In addition, a significant decrease in abacavir Cmax (34%) and increase in Tmax (67%) were noted, but no changes in overall abacavir clearance or half-life were reported. The clinical significance regarding abacavir therapy is not known.
Abacavir; Dolutegravir; Lamivudine: (Moderate) In a study of 11 adult HIV-infected subjects receiving methadone maintenance therapy (40 to 90 mg/day) and abacavir 600 mg twice daily (twice the current recommended dose), methadone clearance increased by 22% (6% to 42%). While this interaction will not require dosage adjustment in the majority of patients, a small number of patients may require increased doses of methadone. In addition, a significant decrease in abacavir Cmax (34%) and increase in Tmax (67%) were noted, but no changes in overall abacavir clearance or half-life were reported. The clinical significance regarding abacavir therapy is not known.
Abacavir; Lamivudine, 3TC: (Moderate) In a study of 11 adult HIV-infected subjects receiving methadone maintenance therapy (40 to 90 mg/day) and abacavir 600 mg twice daily (twice the current recommended dose), methadone clearance increased by 22% (6% to 42%). While this interaction will not require dosage adjustment in the majority of patients, a small number of patients may require increased doses of methadone. In addition, a significant decrease in abacavir Cmax (34%) and increase in Tmax (67%) were noted, but no changes in overall abacavir clearance or half-life were reported. The clinical significance regarding abacavir therapy is not known.
Abacavir; Lamivudine, 3TC; Zidovudine, ZDV: (Moderate) In a study of 11 adult HIV-infected subjects receiving methadone maintenance therapy (40 to 90 mg/day) and abacavir 600 mg twice daily (twice the current recommended dose), methadone clearance increased by 22% (6% to 42%). While this interaction will not require dosage adjustment in the majority of patients, a small number of patients may require increased doses of methadone. In addition, a significant decrease in abacavir Cmax (34%) and increase in Tmax (67%) were noted, but no changes in overall abacavir clearance or half-life were reported. The clinical significance regarding abacavir therapy is not known. (Moderate) Methadone increases exposure zidovudine, ZDV. Patients should be monitored for zidovudine toxicity during concurrent methadone treatment; however, the manufacturer of zidovudine states that routine dosage adjustment of zidovudine is not required during coadministration of methadone. Patients who receive both methadone and zidovudine may experience symptoms characteristic of opiate withdrawal and attribute the cause to decreased methadone levels due to zidovudine. However, it is more likely patients are actually experiencing zidovudine side effects due to increased levels since zidovudine has no effect on methadone metabolism. In one pharmacokinetic study (n=9), coadministration of methadone increased the AUC of zidovudine by about 43% (range: 16-64%). It appears methadone inhibits zidovudine glucuronidation and, to a lesser extent, decreases zidovudine renal clearance.
Abarelix: (Contraindicated) Since abarelix can cause QT prolongation, abarelix should be used cautiously, if at all, with other drugs that are associated with QT prolongation, such as methadone.
Abiraterone: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of abiraterone is necessary. If abiraterone is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate, and coadministration with CYP2D6 inhibitors like abiraterone can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If abiraterone is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Acetaminophen; Aspirin; Diphenhydramine: (Major) Reserve concomitant use of opioids and diphenhydramine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Acetaminophen; Caffeine; Dihydrocodeine: (Major) Concomitant use of methadone with another CNS depressant like dihydrocodeine can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also, consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Acetaminophen; Caffeine; Pyrilamine: (Moderate) Concomitant use of opioid agonists with pyrilamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with pyrilamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Acetaminophen; Chlorpheniramine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Acetaminophen; Chlorpheniramine; Dextromethorphan: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Acetaminophen; Chlorpheniramine; Phenylephrine : (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Acetaminophen; Codeine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Acetaminophen; Dextromethorphan; Doxylamine: (Major) Reserve concomitant use of opioids and doxylamine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Acetaminophen; Diphenhydramine: (Major) Reserve concomitant use of opioids and diphenhydramine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Acetaminophen; Hydrocodone: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Acetaminophen; Oxycodone: (Major) Concomitant use of methadone with another CNS depressant, such as oxycodone, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also, consider a using a lower dose of the CNS depressant; use an initial dose of oxycodone at one-third to one-half the usual dosage. Monitor patients for sedation and respiratory depression.
Acetaminophen; Pamabrom; Pyrilamine: (Moderate) Concomitant use of opioid agonists with pyrilamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with pyrilamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Acetohydroxamic Acid: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Acidifying Agents: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Acrivastine; Pseudoephedrine: (Major) Avoid coadministration of opioid agonists with acrivastine due to the risk of additive CNS depression.
Adagrasib: (Major) Avoid concomitant use of adagrasib and methadone due to the potential for increased methadone exposure and additive risk for QT/QTc prolongation and torsade de pointes (TdP). If use is necessary, consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation. Additionally, consider taking steps to minimize the risk for QT prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring. Methadone is a CYP2C9, CYP2D6, and CYP3A substrate, adagrasib is a moderate CYP2C9, moderate CYP2D6, and strong CYP3A inhibitor, and both medications have been associated with QT interval prolongation.
Aldesleukin, IL-2: (Moderate) Aldesleukin, IL-2 may affect CNS function significantly. Therefore, psychotropic pharmacodynamic interactions could occur following concomitant administration of drugs with significant CNS or psychotropic activity such as opiate agonists. In addition, aldesleukin, IL-2, is a CYP3A4 inhibitor and may increase oxycodone plasma concentrations and related toxicities including potentially fatal respiratory depression. If therapy with both agents is necessary, monitor patients for an extended period and adjust oxycodone dosage as necessary.
Alfentanil: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Alfuzosin: (Major) Due to a possible risk for QT prolongation and torsade de pointes (TdP), alfuzosin and methadone should be used together cautiously. Based on electrophysiology studies performed by the manufacturer, alfuzosin has a slight effect to prolong the QT interval. The QT prolongation appeared less with alfuzosin 10 mg than with 40 mg. The manufacturer warns that the QT effect of alfuzosin should be considered prior to administering the drug to patients taking other medications known to prolong the QT interval. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Almotriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Alosetron: (Major) Patients taking medications that decrease GI motility may be at greater risk for serious complications from alosetron, like constipation, via a pharmacodynamic interaction. Constipation is the most frequently reported adverse effect with alosetron. Alosetron, if used with drugs such as opiate agonists, may seriously worsen constipation, leading to events such as GI obstruction/impaction or paralytic ileus.
Alprazolam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Alvimopan: (Moderate) Patients should not take alvimopan if they have received therapeutic doses of opiate agonists for more than seven consecutive days immediately before initiation of alvimopan therapy. Patients recently exposed to opioids are expected to be more sensitive to the effects of mu-opioid receptor antagonists and may experience adverse effects localized to the gastrointestinal tract such as abdominal pain, nausea, vomiting, and diarrhea.
Amide local anesthetics: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Amiloride: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when amiloride is administered with methadone. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
Amiloride; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when amiloride is administered with methadone. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
Amiodarone: (Major) The need to coadminister methadone with amiodarone should be done with extreme caution and a careful assessment of treatment risks versus benefits. At high doses, methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses averaging approximately 400 mg/day in adult patients. Amiodarone, a Class III antiarrhythmic agent, is associated with a well-established risk of QT prolongation and TdP. Although the frequency of TdP is less with amiodarone than with other Class III agents, amiodarone is still associated with a risk of TdP. Due to the extremely long half-life of amiodarone, a drug interaction is possible for days to weeks after discontinuation of amiodarone. In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with inhibitors of these enzymes, such as amiodarone, may result in increased serum concentrations of methadone.
Amisulpride: (Major) Monitor ECGs for QT prolongation when amisulpride is administered with methadone. Amisulpride causes dose- and concentration- dependent QT prolongation. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Amitriptyline: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Amlodipine: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Amlodipine; Atorvastatin: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Amlodipine; Benazepril: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Amlodipine; Celecoxib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of celecoxib is necessary. If celecoxib is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate, and coadministration with CYP2D6 inhibitors like celecoxib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If celecoxib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Amlodipine; Olmesartan: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Amlodipine; Valsartan: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Amlodipine; Valsartan; Hydrochlorothiazide, HCTZ: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Amobarbital: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Amoxapine: (Major) Concomitant use of opioid agonists with amoxapine may cause excessive sedation and somnolence. Limit the use of opioid pain medications with amoxapine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Amoxicillin; Clarithromycin; Omeprazole: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as clarithromycin, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with clarithromycin, an inhibitor of CYP3A4 and P-gp, may result in increased serum concentrations of methadone.
Amphetamine: (Moderate) If concomitant use of methadone and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Amphetamine; Dextroamphetamine: (Moderate) If concomitant use of methadone and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Amphetamines: (Moderate) If concomitant use of methadone and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Anagrelide: (Major) Torsades de pointes (TdP) and ventricular tachycardia have been reported during post-marketing use of anagrelide. A cardiovascular examination, including an ECG, should be obtained in all patients prior to initiating anagrelide therapy. Monitor patients during anagrelide therapy for cardiovascular effects and evaluate as necessary. Drugs with a possible risk for QT prolongation and TdP that should be used cautiously and with close monitoring with anagrelide include methadone.
Anticholinergics: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when methadone is used concomitantly with an anticholinergic drug. The concomitant use of methadone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
Apalutamide: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with apalutamide is necessary; these effects may be more pronounced with concomitant use of drugs that can induce multiple CYP enzymes. Consider increasing the dose of methadone as needed. If apalutamide is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a substrate of CYP2C9, CYP2C19, and CYP3A4. Apalutamide is a strong CYP3A4 and CYP2C19 inducer, as well as a weak CYP2C9 inducer. Concomitant use with CYP3A4 inducers can decrease methadone levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Apomorphine: (Major) Due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering methadone with apomorphine. The need to coadminister these drugs should be done with extreme caution and a careful assessment of treatment risks versus benefits. Dose-related QTc prolongation is associated with therapeutic apomorphine exposure. Methadone is associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Additionally, apomorphine and methadone can cause significant somnolence which may be additive. A dose reduction of one or both drugs may be warranted.
Apraclonidine: (Minor) Theoretically, apraclonidine might potentiate the effects of CNS depressant drugs such as opiate agonists. Although no specific drug interactions were identified with systemic agents and apraclonidine during clinical trials, apraclonidine can cause dizziness and somnolence.
Aprepitant, Fosaprepitant: (Major) Use caution if methadone and aprepitant, fosaprepitant are used concurrently, and monitor for an increase in methadone-related adverse effects, including excess sedation, for several days after administration of a multi-day aprepitant regimen. Methadone is a CYP3A4 substrate. Aprepitant, when administered as a 3-day oral regimen (125 mg/80 mg/80 mg), is a moderate CYP3A4 inhibitor and inducer and may increase plasma concentrations of methadone. For example, a 5-day oral aprepitant regimen increased the AUC of another CYP3A4 substrate, midazolam (single dose), by 2.3-fold on day 1 and by 3.3-fold on day 5. After a 3-day oral aprepitant regimen, the AUC of midazolam (given on days 1, 4, 8, and 15) increased by 25% on day 4, and then decreased by 19% and 4% on days 8 and 15, respectively. As a single 125 mg or 40 mg oral dose, the inhibitory effect of aprepitant on CYP3A4 is weak, with the AUC of midazolam increased by 1.5-fold and 1.2-fold, respectively. After administration, fosaprepitant is rapidly converted to aprepitant and shares many of the same drug interactions. However, as a single 150 mg intravenous dose, fosaprepitant only weakly inhibits CYP3A4 for a duration of 2 days; there is no evidence of CYP3A4 induction. Fosaprepitant 150 mg IV as a single dose increased the AUC of midazolam (given on days 1 and 4) by approximately 1.8-fold on day 1; there was no effect on day 4. Less than a 2-fold increase in the midazolam AUC is not considered clinically important. Aprepitant is also a CYP2C9 inducer and methadone is a CYP2C9 substrate. Administration of a CYP2C9 substrate, tolbutamide, on days 1, 4, 8, and 15 with a 3-day regimen of oral aprepitant (125 mg/80 mg/80 mg) decreased the tolbutamide AUC by 23% on day 4, 28% on day 8, and 15% on day 15. The AUC of tolbutamide was decreased by 8% on day 2, 16% on day 4, 15% on day 8, and 10% on day 15 when given prior to oral administration of aprepitant 40 mg on day 1, and on days 2, 4, 8, and 15. The effects of aprepitant on tolbutamide were not considered significant.
Aripiprazole: (Major) Aripiprazole should be used cautiously and with close monitoring with methadone due to the potential for increased risk of QT prolongation, torsade de pointes (TdP), and additive CNS depressant effects. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression and QT prolongation. QT prolongation has occurred during therapeutic use of aripiprazole and following overdose. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Arsenic Trioxide: (Major) If possible, drugs that are known to prolong the QT interval should be discontinued prior to initiating arsenic trioxide therapy. QT prolongation should be expected with the administration of arsenic trioxide. Torsade de pointes (TdP) and complete atrioventricular block have been reported. Drugs with a possible risk for QT prolongation and TdP that should be used cautiously with arsenic trioxide include methadone. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Artemether; Lumefantrine: (Major) Artemether; lumefantrine is an inhibitor of and methadone is partially metabolized by the CYP2D6 isoenzyme; therefore, coadministration may lead to increased methadone concentrations. Furthermore, although there are no studies examining the effects of artemether; lumefantrine in patients receiving other QT prolonging drugs, coadministration of such drugs may result in additive QT prolongation. Concomitant use of artemether; lumefantrine with drugs that may prolong the QT interval, such as methadone, should be avoided. Consider ECG monitoring if methadone must be used with or after artemether; lumefantrine treatment.
Articaine; Epinephrine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Asciminib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of asciminib is necessary. If asciminib is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; asciminib is a CYP2C9 and CYP3A inhibitor. Concomitant use with asciminib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Asenapine: (Major) Avoid coadministration of asenapine and methadone due to an additive risk of QT prolongation. Concomitant use of opioid agonists with asenapine may also cause excessive sedation and somnolence. Limit the use of opioid pain medications with asenapine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Asenapine has been associated with QT prolongation. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Aspirin, ASA; Butalbital; Caffeine: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Aspirin, ASA; Caffeine; Orphenadrine: (Major) Concomitant use of methadone with orphenadrine may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with orphenadrine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Aspirin, ASA; Carisoprodol: (Major) Concomitant use of methadone with carisoprodol may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with carisoprodol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Aspirin, ASA; Carisoprodol; Codeine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Major) Concomitant use of methadone with carisoprodol may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with carisoprodol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Aspirin, ASA; Oxycodone: (Major) Concomitant use of methadone with another CNS depressant, such as oxycodone, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also, consider a using a lower dose of the CNS depressant; use an initial dose of oxycodone at one-third to one-half the usual dosage. Monitor patients for sedation and respiratory depression.
Atazanavir: (Moderate) Caution is advised with the coadministration of atazanavir and methadone as concurrent use may result in increased concentrations of methadone. Methadone is primarily metabolized by CYP3A4; atazanavir is a CYP3A4 inhibitor. No clinically significant drug interaction was observed when atazanavir was coadministered with a stable maintenance dose of methadone. However, if coadministered, patients should be regularly monitored for excessive methadone-related side effects, as the theoretical possibility for atazanavir to inhibit methadone metabolism does exist.
Atazanavir; Cobicistat: (Moderate) Caution is advised with the coadministration of atazanavir and methadone as concurrent use may result in increased concentrations of methadone. Methadone is primarily metabolized by CYP3A4; atazanavir is a CYP3A4 inhibitor. No clinically significant drug interaction was observed when atazanavir was coadministered with a stable maintenance dose of methadone. However, if coadministered, patients should be regularly monitored for excessive methadone-related side effects, as the theoretical possibility for atazanavir to inhibit methadone metabolism does exist. (Moderate) The plasma concentrations of methadone may be elevated when administered concurrently with cobicistat. When initiating methadone in patients currently on a regimen containing cobicistat and atazanavir or darunavir, use the lowest methadone starting dose and slowly titrate to desired effect. When initiating antiretroviral regimens containing cobicistat and atazanavir or darunavir to patients on methadone, an adjustment of methadone dose may be needed. Monitoring for adverse effects, such as CNS side effects or respiratory depression, is recommended during coadministration. Methadone is metabolized primarily by the cytochrome P450 isoenzymes CYP2C19, CYP3A4, and CYP2B6, and to a lesser extent, by CYP2C9 and CYP2D6. Methadone also is a substrate of P-glycoprotein (P-gp). Cobicistat is an inhibitor of CYP3A4, CYP2D6, and P-gp.
Atomoxetine: (Major) Concomitant use of methadone and atomoxetine increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Atropine; Difenoxin: (Moderate) Concurrent administration of diphenoxylate/difenoxin with other opiate agonists can potentiate the CNS-depressant effects of diphenoxylate/difenoxin. Use caution during coadministration. In addition, diphenoxylate/difenoxin use may cause constipation; cases of severe GI reactions including toxic megacolon and adynamic ileus have been reported. Reduced GI motility when combined with opiate agonists may increase the risk of serious GI related adverse events.
Avacopan: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of avacopan is necessary. If avacopan is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; avacopan is a weak CYP3A inhibitor. Concomitant use with avacopan can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Azelastine: (Major) Concomitant use of opioid agonists with azelastine may cause excessive sedation and somnolence. Limit the use of opioid pain medications with azelastine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Azelastine; Fluticasone: (Major) Concomitant use of opioid agonists with azelastine may cause excessive sedation and somnolence. Limit the use of opioid pain medications with azelastine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Azithromycin: (Major) Concomitant use of azithromycin and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Baclofen: (Major) Concomitant use of methadone with baclofen may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with baclofen to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Barbiturates: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Bedaquiline: (Major) Due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering bedaquiline with methadone. The need to coadminister these drugs should be done with extreme caution and a careful assessment of treatment risks versus benefits. Bedaquiline has been reported to prolong the QT interval. Prior to initiating bedaquiline, obtain serum electrolyte concentrations and a baseline ECG. An ECG should also be performed at least 2, 12, and 24 weeks after starting bedaquiline therapy. Methadone is also considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Belladonna; Opium: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract; severe constipation or paralytic ileus is possible, especially with chronic use. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also, consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Belumosudil: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of belumosudil is necessary. If belumosudil is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; belumosudil is a weak CYP3A inhibitor. Concomitant use with belumosudil can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Belzutifan: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with belzutifan is necessary. Consider increasing the dose of methadone as needed. If belzutifan is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; belzutifan is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Benzhydrocodone; Acetaminophen: (Major) Concomitant use of opioid agonists with benzhydrocodone may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of benzhydrocodone with opioid agonists to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If benzhydrocodone is initiated in a patient taking methadone, reduce initial dosage and titrate to clinical response. If methadone is prescribed in a patient taking benzhydrocodone, use a lower initial dose of methadone and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation. Careful monitoring, particularly during treatment initiation and dose adjustment, is recommended during coadministration of benzhydrocodone and methadone because of the potential risk of serotonin syndrome. Discontinue benzhydrocodone if serotonin syndrome is suspected. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. Serotonin syndrome, in its most severe form, can resemble neuroleptic malignant syndrome.
Benzoic Acid; Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate: (Major) Avoid concomitant use of methadone in patients receiving methylene blue or within 14 days of stopping treatment with methylene blue due to the risk of serotonin syndrome or opioid toxicity, including respiratory depression. If cannot avoid use, choose the lowest possible methylene blue dose and observe the patient closely for up to 4 hours after administration.
Benzphetamine: (Moderate) If concomitant use of methadone and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Berotralstat: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of berotralstat is necessary. If berotralstat is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4 and CYP2D6; berotralstat is a moderate CYP3A4 and CYP2D6 inhibitor. Concomitant use with berotralstat can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Bethanechol: (Moderate) Bethanechol facilitates intestinal and bladder function via parasympathomimetic actions. Opiate agonists impair the peristaltic activity of the intestine. Thus, these drugs can antagonize the beneficial actions of bethanechol on GI motility.
Bicalutamide: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of bicalutamide is necessary. If bicalutamide is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; bicalutamide is a weak CYP3A4 enzyme inhibitor. Concomitant use with bicalutamide can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose o
Bismuth Subcitrate Potassium; Metronidazole; Tetracycline: (Major) Concomitant use of metronidazole and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary. (Moderate) Additive constipation may be seen with concurrent use of opiate agonists and antidiarrheals. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
Bismuth Subsalicylate: (Moderate) Additive constipation may be seen with concurrent use of opiate agonists and antidiarrheals. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
Bismuth Subsalicylate; Metronidazole; Tetracycline: (Major) Concomitant use of metronidazole and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary. (Moderate) Additive constipation may be seen with concurrent use of opiate agonists and antidiarrheals. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
Bosentan: (Moderate) Bosentan is an inducer of cytochrome P450 enzymes, specifically the CYP2C9 and CYP3A4 isoenzymes, and may decrease concentrations of drugs metabolized by these enzymes including methadone.
Brexanolone: (Moderate) Concomitant use of brexanolone with CNS depressants like the opiate agonists may increase the likelihood or severity of adverse reactions related to sedation and additive CNS depression. Monitor for excessive sedation, dizziness, and a potential for loss of consciousness during brexanolone use.
Brexpiprazole: (Major) Concomitant use of opioid agonists with brexpiprazole may cause excessive sedation and somnolence. Limit the use of opioid pain medications with brexpiprazole to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Brigatinib: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with brigatinib is necessary. Consider increasing the dose of methadone as needed. If brigatinib is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; brigatinib is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Brimonidine: (Moderate) Based on the sedative effects of brimonidine in individual patients, brimonidine administration has potential to enhance the CNS depressants effects of opiate agonists.
Brimonidine; Brinzolamide: (Moderate) Based on the sedative effects of brimonidine in individual patients, brimonidine administration has potential to enhance the CNS depressants effects of opiate agonists.
Brimonidine; Timolol: (Moderate) Based on the sedative effects of brimonidine in individual patients, brimonidine administration has potential to enhance the CNS depressants effects of opiate agonists.
Brompheniramine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Brompheniramine; Dextromethorphan; Phenylephrine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Brompheniramine; Phenylephrine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Brompheniramine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Brompheniramine; Pseudoephedrine; Dextromethorphan: (Moderate) Concomitant use of opioid agonists with brompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with brompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Bumetanide: (Moderate) Diuretics can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with diuretics is needed.
Bupivacaine Liposomal: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Bupivacaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Bupivacaine; Epinephrine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Bupivacaine; Lidocaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Bupivacaine; Meloxicam: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Buprenorphine: (Major) Buprenorphine has been associated with QT prolongation and has a possible risk of torsade de pointes (TdP). Methadone has a possible risk for QT prolongation and TdP and use with buprenorphine should be avoided if possible. FDA-approved labeling for some buprenorphine products recommend avoiding use with Class 1A and Class III antiarrhythmic medications while other labels recommend avoiding use with any drug that has the potential to prolong the QT interval. Buprenorphine is a mixed opiate agonist/antagonist with strong affinity for the mu-receptor that may partially block the effects of full mu-receptor opiate agonists and reduce analgesic effects. In some cases of acute pain, trauma, or during surgical management, opiate-dependent patients receiving buprenorphine maintenance therapy may require concurrent treatment with opiate agonists, such as methadone. In these cases, health care professionals must exercise caution in opiate agonist dose selection, as higher doses of an opiate agonist may be required to compete with buprenorphine at the mu-receptor. Management strategies may include adding a short-acting opiate agonist to achieve analgesia in the presence of buprenorphine, discontinuation of buprenorphine and use of an opiate agonist to avoid withdrawal and achieve analgesia, or conversion of buprenorphine to methadone while using additional opiate agonists if needed. Closely monitor patients for CNS or respiratory depression. When buprenorphine is used for analgesia, avoid co-use with opiate agonists. Buprenorphine may cause withdrawal symptoms in patients receiving chronic opiate agonists as well as possibly potentiate CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
Buprenorphine; Naloxone: (Major) Buprenorphine has been associated with QT prolongation and has a possible risk of torsade de pointes (TdP). Methadone has a possible risk for QT prolongation and TdP and use with buprenorphine should be avoided if possible. FDA-approved labeling for some buprenorphine products recommend avoiding use with Class 1A and Class III antiarrhythmic medications while other labels recommend avoiding use with any drug that has the potential to prolong the QT interval. Buprenorphine is a mixed opiate agonist/antagonist with strong affinity for the mu-receptor that may partially block the effects of full mu-receptor opiate agonists and reduce analgesic effects. In some cases of acute pain, trauma, or during surgical management, opiate-dependent patients receiving buprenorphine maintenance therapy may require concurrent treatment with opiate agonists, such as methadone. In these cases, health care professionals must exercise caution in opiate agonist dose selection, as higher doses of an opiate agonist may be required to compete with buprenorphine at the mu-receptor. Management strategies may include adding a short-acting opiate agonist to achieve analgesia in the presence of buprenorphine, discontinuation of buprenorphine and use of an opiate agonist to avoid withdrawal and achieve analgesia, or conversion of buprenorphine to methadone while using additional opiate agonists if needed. Closely monitor patients for CNS or respiratory depression. When buprenorphine is used for analgesia, avoid co-use with opiate agonists. Buprenorphine may cause withdrawal symptoms in patients receiving chronic opiate agonists as well as possibly potentiate CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
Bupropion: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of bupropion is necessary. If bupropion is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; bupropion is a strong CYP2D6 inhibitor. Concomitant use with bupropion can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Bupropion; Naltrexone: (Major) When naltrexone is used as adjuvant treatment of opiate or alcohol dependence, use is contraindicated in patients currently receiving opiate agonists. Naltrexone will antagonize the therapeutic benefits of opiate agonists and will induce a withdrawal reaction in patients with physical dependence to opioids. Also, patients should be opiate-free for at least 7-10 days prior to initiating naltrexone therapy. If there is any question of opioid use in the past 7-10 days and the patient is not experiencing opioid withdrawal symptoms and/or the urine is negative for opioids, a naloxone challenge test needs to be performed. If a patient receives naltrexone, and an opiate agonist is needed for an emergency situation, large doses of opiate agonists may ultimately overwhelm naltrexone antagonism of opiate receptors. Immediately following administration of exogenous opiate agonists, the opiate plasma concentration may be sufficient to overcome naltrexone competitive blockade, but the patient may experience deeper and more prolonged respiratory depression and thus, may be in danger of respiratory arrest and circulatory collapse. Non-receptor mediated actions like facial swelling, itching, generalized erythema, or bronchoconstriction may occur presumably due to histamine release. A rapidly acting opiate agonist is preferred as the duration of respiratory depression will be shorter. Patients receiving naltrexone may also experience opiate side effects with low doses of opiate agonists. If the opiate agonist is taken in such a way that high concentrations remain in the body beyond the time naltrexone exerts its therapeutic effects, serious side effects may occur. (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of bupropion is necessary. If bupropion is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; bupropion is a strong CYP2D6 inhibitor. Concomitant use with bupropion can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Buspirone: (Moderate) Concomitant use of CNS depressants, such as buspirone, can potentiate the effects of methadone, which may potentially lead to respiratory depression, CNS depression, sedation, or hypotensive responses. If concurrent use of codeine and buspirone is imperative, reduce the dose of one or both drugs.
Butabarbital: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Butalbital; Acetaminophen: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Butalbital; Acetaminophen; Caffeine: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Butalbital; Acetaminophen; Caffeine; Codeine: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone. (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Butalbital; Aspirin; Caffeine; Codeine: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone. (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Butorphanol: (Major) Avoid the concomitant use of butorphanol and opiate agonists, such as methadone. Butorphanol is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Butorphanol may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of butorphanol with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
Cabotegravir; Rilpivirine: (Major) Close clinical monitoring is advised with coadministration. Use of these drugs together may cause the plasma concentration of methadone to decrease, thereby resulting in decreased methadone efficacy. No dose adjustments are required when initiating concurrent treatment; however, the maintenance dose of methadone may need to be adjusted in some patients. In addition, due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering rilpivirine with methadone. A careful assessment of treatment risks versus benefits should be conducted prior to coadministration. When initiating concurrent treatment no dose adjustments are required; however, the dose of methadone may need to be adjusted during maintenance therapy. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Supratherapeutic doses of rilpivirine (75 to 300 mg/day) have also been associated with prolongation of the QT interval.
Calcium, Magnesium, Potassium, Sodium Oxybates: (Major) Concomitant use of opioid agonists with sodium oxybate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medication with sodium oxybate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Cannabidiol: (Moderate) Concomitant use of opioid agonists with cannabidiol may cause excessive sedation and somnolence. Limit the use of opioid pain medications with cannabidiol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Additionally, increased methadone exposure is possible. Methadone is a CYP2C9 substrate. In vitro data predicts inhibition of CYP2C9 by cannabidiol potentially resulting in clinically significant interactions.
Capecitabine: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of capecitabine is necessary. If capecitabine is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2C9 substrate, and coadministration with weak CYP2C9 inhibitors like capecitabine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If capecitabine is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Capsaicin; Metaxalone: (Major) Concomitant use of opioid agonists with metaxalone may cause respiratory depression, profound sedation, and death. Limit the use of opioid pain medication with metaxalone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Consider prescribing naloxone for the emergency treatment of opioid overdose. Concomitant use of metaxalone and opioid agonists increases the risk for serotonin syndrome. Avoid concomitant use if possible and monitor for serotonin syndrome if use is necessary.
Carbamazepine: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with carbamazepine is necessary; consider increasing the dose of methadone as needed. If carbamazepine is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a CYP3A4 substrate and carbamazepine is a strong CYP3A4 inducer. Concomitant use with CYP3A4 inducers can decrease methadone levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Carbinoxamine: (Moderate) Concomitant use of opioid agonists with carbinoxamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with carbinoxamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Carbonic anhydrase inhibitors: (Moderate) Carbonic anhydrase inhibitors can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with diuretics is needed.
Cariprazine: (Moderate) Concomitant use of opioid agonists like methadone with cariprazine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with cariprazine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Carisoprodol: (Major) Concomitant use of methadone with carisoprodol may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with carisoprodol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Carvedilol: (Moderate) Increased concentrations of methadone may occur if it is coadministered with carvedilol; exercise caution. Carvedilol is a P-glycoprotein (P-gp) inhibitor and methadone is a P-gp substrate.
Celecoxib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of celecoxib is necessary. If celecoxib is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate, and coadministration with CYP2D6 inhibitors like celecoxib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If celecoxib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Celecoxib; Tramadol: (Major) Concomitant use of tramadol increases the seizure risk in patients taking opiate agonists. Also, tramadol can cause additive CNS depression and respiratory depression when used with opiate agonists; avoid concurrent use whenever possible. If used together, extreme caution is needed, and a reduced tramadol dose is recommended. (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of celecoxib is necessary. If celecoxib is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate, and coadministration with CYP2D6 inhibitors like celecoxib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If celecoxib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Cenobamate: (Moderate) Concomitant use of methadone with cenobamate may cause excessive sedation and somnolence. Limit the use of methadone with cenobamate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Additionally, monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with cenobamate is necessary; these effects may be more pronounced with cenobamate as it can induce multiple CYP enzymes. Consider increasing the dose of methadone as needed. If cenobamate is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a substrate of CYP3A4 and CYP2B6; cenobamate is a moderate CYP3A4 inducer and weak CYP2B6 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Ceritinib: (Major) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of ceritinib is necessary; carefully assess the benefits of treatment with the risks of therapy, including QT prolongation. Periodically monitor ECGs for QT prolongation and monitor electrolytes. An interruption of ceritinib therapy, dose reduction, or discontinuation of therapy may be necessary for QT prolongation. If ceritinib is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP3A4 substrate, and coadministration with strong CYP3A4 inhibitors like ceritinib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If ceritinib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Additionally, concentration-dependent QT prolongation has been reported with ceritinib therapy. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Cetirizine: (Major) Reserve concomitant use of opioids and cetirizine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Cetirizine; Pseudoephedrine: (Major) Reserve concomitant use of opioids and cetirizine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Chlophedianol; Dexbrompheniramine: (Moderate) Concomitant use of opioid agonists with dexbrompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexbrompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlophedianol; Dexchlorpheniramine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with dexchlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexchlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorcyclizine: (Moderate) Concomitant use of opioid agonists with chlorcyclizine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorcyclizine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlordiazepoxide: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Chlordiazepoxide; Amitriptyline: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus. (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Chlordiazepoxide; Clidinium: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Chloroquine: (Major) Avoid coadministration of chloroquine with methadone due to the increased risk of QT prolongation. If use together is necessary, obtain an ECG at baseline to assess initial QT interval and determine frequency of subsequent ECG monitoring, avoid any non-essential QT prolonging drugs, and correct electrolyte imbalances. Chloroquine is associated with an increased risk of QT prolongation and torsade de pointes (TdP); the risk of QT prolongation is increased with higher chloroquine doses. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Chlorpheniramine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Codeine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Dextromethorphan: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Major) Concomitant use of methadone with another CNS depressant like dihydrocodeine can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also, consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Hydrocodone: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Ibuprofen; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Phenylephrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpheniramine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with chlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with chlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorpromazine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with inhibitors of these enzymes may result in increased serum concentrations of methadone. Chlorpromazine is specifically associated with an established risk of QT prolongation and TdP and inhibits CYP2D6. In addition, concomitant use of methadone with another CNS depressant, such as chlorpromazine, can also lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Chlorthalidone; Clonidine: (Major) Concomitant use of opioid agonists with clonidine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with clonidine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Chlorzoxazone: (Major) Concomitant use of methadone with chlorzoxazone may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with chlorzoxazone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Cinacalcet: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of cinacalcet is necessary. If cinacalcet is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; cinacalcet is a moderate CYP2D6 inhibitor. Concomitant use with cinacalcet can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Ciprofloxacin: (Major) Concomitant use of ciprofloxacin and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Cisapride: (Contraindicated) Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Because of the potential for TdP, use of cisapride with methadone is contraindicated.
Citalopram: (Major) Coadministration may increase the risk of serotonin syndrome, QT prolongation, or torsade de pointes (TdP). Citalopram causes dose-dependent QT interval prolongation. According to the manufacturer of citalopram, ECG monitoring is recommended in patients receiving concurrent drugs that prolong the QT interval. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, both citalopram and methadone have central serotonergic properties and serotonin syndrome is possible. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical treatment should be implemented.
Clarithromycin: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as clarithromycin, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with clarithromycin, an inhibitor of CYP3A4 and P-gp, may result in increased serum concentrations of methadone.
Clemastine: (Moderate) Concomitant use of opioid agonists with clemastine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with clemastine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Clobazam: (Major) Concomitant use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If methadone is initiated in a patient taking a benzodiazepine, reduced dosages are recommended; in opioid-naive adults, use an initial dose of methadone 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Clofazimine: (Major) Concomitant use of clofazimine and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Clomipramine: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Clonazepam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Clonidine: (Major) Concomitant use of opioid agonists with clonidine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with clonidine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Clopidogrel: (Moderate) Coadministration of opioid agonists, such as methadone, delay and reduce the absorption of clopidogrel resulting in reduced exposure to active metabolites and diminished inhibition of platelet aggregation. Consider the use of a parenteral antiplatelet agent in acute coronary syndrome patients requiring an opioid agonist. Coadministration of intravenous morphine decreased the Cmax and AUC of clopidogrel's active metabolites by 34%. Time required for maximal inhibition of platelet aggregation (median 3 hours vs. 1.25 hours) was significantly delayed; times up to 5 hours were reported. Inhibition of platelet plug formation was delayed and residual platelet aggregation was significantly greater 1 to 4 hours after morphine administration.
Clorazepate: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Clozapine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as clozapine, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, concomitant use of methadone with another CNS depressant, such as clozapine, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; ; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Consider a lower dose of the CNS depressant. In addition, combining clozapine with opiate agonists may lead to additive effects on intestinal motility or bladder function.
Cobicistat: (Moderate) The plasma concentrations of methadone may be elevated when administered concurrently with cobicistat. When initiating methadone in patients currently on a regimen containing cobicistat and atazanavir or darunavir, use the lowest methadone starting dose and slowly titrate to desired effect. When initiating antiretroviral regimens containing cobicistat and atazanavir or darunavir to patients on methadone, an adjustment of methadone dose may be needed. Monitoring for adverse effects, such as CNS side effects or respiratory depression, is recommended during coadministration. Methadone is metabolized primarily by the cytochrome P450 isoenzymes CYP2C19, CYP3A4, and CYP2B6, and to a lesser extent, by CYP2C9 and CYP2D6. Methadone also is a substrate of P-glycoprotein (P-gp). Cobicistat is an inhibitor of CYP3A4, CYP2D6, and P-gp.
Codeine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Codeine; Guaifenesin: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Codeine; Guaifenesin; Pseudoephedrine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Codeine; Phenylephrine; Promethazine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Drugs with a potential risk for QT prolongation that should be used cautiously with methadone include promethazine. Additionally, use of methadone with another CNS depressant can lead to additive sedation, respiratory depression, hypotension, or coma. Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; for example, in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Codeine; Promethazine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Drugs with a potential risk for QT prolongation that should be used cautiously with methadone include promethazine. Additionally, use of methadone with another CNS depressant can lead to additive sedation, respiratory depression, hypotension, or coma. Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; for example, in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
COMT inhibitors: (Major) Concomitant use of opioid agonists with COMT inhibitors may cause excessive sedation and somnolence. Limit the use of opioid pain medications with COMT inhibitors to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. COMT inhibitors have also been associated with sudden sleep onset during activities of daily living such as driving, which has resulted in accidents in some cases. Prescribers should re-assess patients for drowsiness or sleepiness regularly throughout treatment, especially since events may occur well after the start of treatment.
Conivaptan: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of conivaptan is necessary. If conivaptan is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; conivaptan is a moderate CYP3A inhibitor. Concomitant use with conivaptan can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Crizotinib: (Major) Avoid coadministration of crizotinib with methadone due to the risk of QT prolongation; exposure to methadone may also increase. If concomitant use is unavoidable, monitor ECGs for QT prolongation and monitor electrolytes. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation. An interruption of therapy, dose reduction, or discontinuation of therapy may be necessary for crizotinib patients if QT prolongation occurs. If crizotinib is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP3A4 substrate considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Crizotinib is a moderate CYP3A inhibitor that has also been associated with concentration-dependent QT prolongation. Coadministration can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If crizotinib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Crofelemer: (Moderate) Pharmacodynamic interactions between crofelemer and opiate agonists are theoretically possible. Crofelemer does not affect GI motility mechanisms, but does have antidiarrheal effects. Patients taking medications that decrease GI motility, such as opiate agonists, may be at greater risk for serious complications from crofelemer, such as constipation with chronic use. Use caution and monitor GI symptoms during coadministration.
Cyclizine: (Moderate) Concomitant use of opioid agonists with cyclizine may cause excessive sedation and somnolence. Limit the use of opioid pain medications with cyclizine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Cyclobenzaprine: (Major) Concomitant use of methadone with cyclobenzaprine may cause respiratory depression, hypotension, profound sedation, and death. Additionally, concomitant use may result in serotonin syndrome. Limit the use of opioid pain medications with cyclobenzaprine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Cyproheptadine: (Moderate) Concomitant use of opioid agonists with cyproheptadine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with cyproheptadine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Dacomitinib: (Moderate) Concomitant use of methadone with dacomitinib may increase methadone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. If coadministration is necessary, monitor patients closely at frequent intervals and consider a dosage reduction of methadone until stable drug effects are achieved. Discontinuation of dacomitinib could decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to methadone. If dacomitinib is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Methadone is a substrate for CYP2D6. Dacomitinib is a strong inhibitor of CYP2D6.
Dalfopristin; Quinupristin: (Moderate) Concomitant use of methadone with dalfopristin; quinupristin may increase methadone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of methadone until stable drug effects are achieved. Discontinuation of dalfopristin; quinupristin could decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to methadone. If dalfopristin; quinupristin is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Methadone is a substrate for CYP3A4. Dalfopristin; quinupristin is a weak inhibitor of CYP3A4.
Danazol: (Moderate) Danazol is a CYP3A4 inhibitor and can decrease the hepatic metabolism of drugs that are CYP3A4 substrates including methadone.
Dantrolene: (Major) Concomitant use of methadone with dantrolene may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with dantrolene to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Daridorexant: (Major) Concomitant use of opiate agonists with daridorexant may cause excessive sedation and somnolence. Limit the use of opiates with daridorexant to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Avoid prescribing cough medicines that contain opiates in patients taking daridorexant.
Darifenacin: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of darifenacin is necessary. If darifenacin is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate, and coadministration with CYP2D6 inhibitors like darifenacin can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If darifenacin is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. In addition, the concomitant use of these drugs together may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Darifenacin has anticholinergic actions that may produce additive effects. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. Both agents may also cause drowsiness or blurred vision, and patients should use care in driving or performing other hazardous tasks until the effects of the drugs are known.
Darunavir: (Moderate) Coadministration of darunavir with methadone is expected to result in decreased methadone concentrations. Patients should be monitored for opiate abstinence syndrome; an increase in methadone dosage may be considered based on clinical response.
Darunavir; Cobicistat: (Moderate) Coadministration of darunavir with methadone is expected to result in decreased methadone concentrations. Patients should be monitored for opiate abstinence syndrome; an increase in methadone dosage may be considered based on clinical response. (Moderate) The plasma concentrations of methadone may be elevated when administered concurrently with cobicistat. When initiating methadone in patients currently on a regimen containing cobicistat and atazanavir or darunavir, use the lowest methadone starting dose and slowly titrate to desired effect. When initiating antiretroviral regimens containing cobicistat and atazanavir or darunavir to patients on methadone, an adjustment of methadone dose may be needed. Monitoring for adverse effects, such as CNS side effects or respiratory depression, is recommended during coadministration. Methadone is metabolized primarily by the cytochrome P450 isoenzymes CYP2C19, CYP3A4, and CYP2B6, and to a lesser extent, by CYP2C9 and CYP2D6. Methadone also is a substrate of P-glycoprotein (P-gp). Cobicistat is an inhibitor of CYP3A4, CYP2D6, and P-gp.
Darunavir; Cobicistat; Emtricitabine; Tenofovir alafenamide: (Moderate) Coadministration of darunavir with methadone is expected to result in decreased methadone concentrations. Patients should be monitored for opiate abstinence syndrome; an increase in methadone dosage may be considered based on clinical response. (Moderate) The plasma concentrations of methadone may be elevated when administered concurrently with cobicistat. When initiating methadone in patients currently on a regimen containing cobicistat and atazanavir or darunavir, use the lowest methadone starting dose and slowly titrate to desired effect. When initiating antiretroviral regimens containing cobicistat and atazanavir or darunavir to patients on methadone, an adjustment of methadone dose may be needed. Monitoring for adverse effects, such as CNS side effects or respiratory depression, is recommended during coadministration. Methadone is metabolized primarily by the cytochrome P450 isoenzymes CYP2C19, CYP3A4, and CYP2B6, and to a lesser extent, by CYP2C9 and CYP2D6. Methadone also is a substrate of P-glycoprotein (P-gp). Cobicistat is an inhibitor of CYP3A4, CYP2D6, and P-gp.
Dasatinib: (Major) Due to a possible risk for QT prolongation and torsade de pointes (TdP), dasatinib and methadone should be used together cautiously. In vitro studies have shown that dasatinib has the potential to prolong cardiac ventricular repolarization (prolong QT interval). The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Degarelix: (Major) The need to coadminister methadone with drugs known to prolong the QT interval like degarelix should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (greater than 200 mg/day; averaging about 400 mg/day in adults). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy (i.e., degarelix) may prolong the QT/QTc interval.
Delavirdine: (Major) The concurrent administration of methadone and inhibitors of cytochrome P450 3A4, such as delavirdine, may result in increased concentrations of methadone. Inhibition of methadone metabolism can lead to toxicity including CNS adverse effects and potential for QT prolongation and torsades de pointes when high doses of methadone are used (e.g., 200 mg/day PO in adult patients). A decrease in methadone doses may be required.
Desflurane: (Moderate) Concurrent use with opiate agonists can decrease the minimum alveolar concentration (MAC) of desflurane needed to produce anesthesia.
Desipramine: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Desmopressin: (Major) Additive hyponatremic effects may be seen in patients treated with desmopressin and drugs associated with water intoxication, hyponatremia, or SIADH including opiate agonists. Use combination with caution, and monitor patients for signs and symptoms of hyponatremia.
Deutetrabenazine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Deutetrabenazine may prolong the QT interval, but the degree of QT prolongation is not clinically significant when deutetrabenazine is administered within the recommended dosage range. Concomitant use of opioid agonists with deutetrabenazine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with deutetrabenazine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Dexamethasone: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with dexamethasone is necessary. Consider increasing the dose of methadone as needed. If dexamethasone is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; dexamethasone is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Dexbrompheniramine: (Moderate) Concomitant use of opioid agonists with dexbrompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexbrompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Dexbrompheniramine; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with dexbrompheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexbrompheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Dexchlorpheniramine: (Moderate) Concomitant use of opioid agonists with dexchlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexchlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Dexchlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Concomitant use of opioid agonists with dexchlorpheniramine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dexchlorpheniramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Dexmedetomidine: (Major) Concomitant use of dexmedetomidine and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary. In addition, if concomitant use is necessary, consider a dose reduction of one or both drugs because of the potential for additive pharmacological effects. Hypotension, profound sedation, coma, respiratory depression, or death may occur during coadministration of methadone and other CNS depressants. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Evaluate the patient's use of alcohol or illicit drugs. Monitor patients for sedation or respiratory depression.
Dextroamphetamine: (Moderate) If concomitant use of methadone and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Dextromethorphan; Bupropion: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of bupropion is necessary. If bupropion is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; bupropion is a strong CYP2D6 inhibitor. Concomitant use with bupropion can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Dextromethorphan; Diphenhydramine; Phenylephrine: (Major) Reserve concomitant use of opioids and diphenhydramine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Dextromethorphan; Quinidine: (Contraindicated) Quinidine administration is associated with QT prolongation and torsades de pointes (TdP). Quinidine inhibits CYP2D6 and has QT-prolonging actions; quinidine is contraindicated with other drugs that prolong the QT interval and are metabolized by CYP2D6 as the effects on the QT interval may be increased during concurrent use of these agents. Drugs that prolong the QT and are substrates for CYP2D6 that are contraindicated with quinidine include methadone.
Diazepam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation. If parenteral diazepam is used with an opiate agonist, reduce the opiate agonist dosage by at least 1/3. Educate patients about the risks and symptoms of respiratory depression and sedation.
Didanosine, ddI: (Major) Methadone decreases the AUC and Cmax of didanosine, ddI. Methadone may slow absorption, and increase first-pass metabolism of didanosine. Methadone decreased the AUC of didanosine tablets by 60% and the Cmax by 64% suggesting that increased doses of didanosine may be required in patients receiving methadone. Do not coadminister methadone with Videx pediatric powder due to significant decreases in didanosine concentrations. If coadministration of methadone and didanosine is necessary, the extended-release capsules are recommended (Videx EC). Patients should be closely monitored for adequate clinical response when the extended-release capsules are coadministered with methadone, including monitoring for changes in HIV RNA viral load.
Difelikefalin: (Major) Avoid concomitant use of opioids and other CNS depressants, such as difelikefalin. Concomitant use can increase the risk of respiratory depression, hypotension, profound sedation, and death. If alternate treatment options are inadequate and coadministration is necessary, limit dosages and durations to the minimum required, monitor patients closely for respiratory depression and sedation, and consider prescribing naloxone for the emergency treatment of opioid overdose.
Diltiazem: (Moderate) Concurrent administration with CYP3A4 inhibitors, such as diltiazem, may result in increased concentrations of methadone. Inhibition of methadone metabolism can lead to toxicity including CNS adverse effects and potential for QT prolongation and torsades de pointes when high doses of methadone are used (e.g., 200 mg/day PO in adult patients).
Dimenhydrinate: (Moderate) Concomitant use of opioid agonists with dimenhydrinate may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dimenhydrinate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Diphenhydramine: (Major) Reserve concomitant use of opioids and diphenhydramine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Diphenhydramine; Ibuprofen: (Major) Reserve concomitant use of opioids and diphenhydramine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Diphenhydramine; Naproxen: (Major) Reserve concomitant use of opioids and diphenhydramine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Diphenhydramine; Phenylephrine: (Major) Reserve concomitant use of opioids and diphenhydramine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Diphenoxylate; Atropine: (Moderate) Concurrent administration of diphenoxylate/difenoxin with other opiate agonists can potentiate the CNS-depressant effects of diphenoxylate/difenoxin. Use caution during coadministration. In addition, diphenoxylate/difenoxin use may cause constipation; cases of severe GI reactions including toxic megacolon and adynamic ileus have been reported. Reduced GI motility when combined with opiate agonists may increase the risk of serious GI related adverse events.
Disopyramide: (Major) The need to coadminister methadone with disopyramide should be done with extreme caution and a careful assessment of treatment risks versus benefits. Disopyramide administration is associated with QT prolongation and torsades de pointes (TdP). Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Dofetilide: (Major) Coadministration of dofetilide and methadone is not recommended as concurrent use may increase the risk of QT prolongation. Dofetilide, a Class III antiarrhythmic agent, is associated with a well-established risk of QT prolongation and torsade de pointes (TdP). Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Dolasetron: (Major) Due to a possible risk for QT prolongation and torsade de pointes (TdP), dolasetron and methadone should be used together cautiously. Dolasetron has been associated with a dose-dependant prolongation in the QT, PR, and QRS intervals on an electrocardiogram. Use of dolasetron injection for the prevention of chemotherapy-induced nausea and vomiting is contraindicated because the risk of QT prolongation is higher with the doses required for this indication; when the injection is used at lower doses (i.e., those approved for post-operative nausea and vomiting) or when the oral formulation is used, the risk of QT prolongation is lower and caution is advised. he need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Dolutegravir; Rilpivirine: (Major) Close clinical monitoring is advised with coadministration. Use of these drugs together may cause the plasma concentration of methadone to decrease, thereby resulting in decreased methadone efficacy. No dose adjustments are required when initiating concurrent treatment; however, the maintenance dose of methadone may need to be adjusted in some patients. In addition, due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering rilpivirine with methadone. A careful assessment of treatment risks versus benefits should be conducted prior to coadministration. When initiating concurrent treatment no dose adjustments are required; however, the dose of methadone may need to be adjusted during maintenance therapy. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Supratherapeutic doses of rilpivirine (75 to 300 mg/day) have also been associated with prolongation of the QT interval.
Donepezil: (Major) Case reports indicate that QT prolongation and torsade de pointes (TdP) can occur during donepezil therapy. Donepezil is considered a drug with a known risk of TdP. Drugs with a possible risk for QT prolongation and TdP that should be used cautiously and with close monitoring with donepezil include methadone.
Donepezil; Memantine: (Major) Case reports indicate that QT prolongation and torsade de pointes (TdP) can occur during donepezil therapy. Donepezil is considered a drug with a known risk of TdP. Drugs with a possible risk for QT prolongation and TdP that should be used cautiously and with close monitoring with donepezil include methadone.
Doxepin: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Doxylamine: (Major) Reserve concomitant use of opioids and doxylamine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Doxylamine; Pyridoxine: (Major) Reserve concomitant use of opioids and doxylamine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Dronabinol: (Moderate) Concomitant use of opioid agonists with dronabinol may cause excessive sedation and somnolence. Limit the use of opioid pain medication with dronabinol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Dronedarone: (Contraindicated) The concomitant use of dronedarone and methadone is contraindicated. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Droperidol: (Major) Droperidol should not be used in combination with any drug known to have potential to prolong the QT interval, such as methadone. Concomitant use of opioid agonists with droperidol may also cause excessive sedation and somnolence. If coadministration cannot be avoided, use extreme caution; initiate droperidol at a low dose and increase the dose as needed to achieve the desired effect. Use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Droperidol administration is associated with an established risk for QT prolongation and torsade de pointes (TdP). Some cases have occurred in patients with no known risk factors for QT prolongation and some cases have been fatal. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Efavirenz: (Major) Coadministration of efavirenz and methadone may increase the risk for QT prolongation and torsade de pointes (TdP). QT prolongation has been observed with use of efavirenz. Although data are limited, the manufacturer of efavirenz recommends an alternative antiretroviral be considered for patients receiving medications with a known risk for TdP. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, efavirenz induces methadone metabolism via CYP3A4 and is associated with significant decreases in methadone concentrations. Clinical reports suggest that patients who are stabilized on methadone-maintenance therapy may experience opiate withdrawal symptoms when efavirenz is added to their HIV-regimen. Methadone-maintained patients should be monitored for evidence of withdrawal and the methadone dose should be adjusted accordingly.
Efavirenz; Emtricitabine; Tenofovir Disoproxil Fumarate: (Major) Coadministration of efavirenz and methadone may increase the risk for QT prolongation and torsade de pointes (TdP). QT prolongation has been observed with use of efavirenz. Although data are limited, the manufacturer of efavirenz recommends an alternative antiretroviral be considered for patients receiving medications with a known risk for TdP. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, efavirenz induces methadone metabolism via CYP3A4 and is associated with significant decreases in methadone concentrations. Clinical reports suggest that patients who are stabilized on methadone-maintenance therapy may experience opiate withdrawal symptoms when efavirenz is added to their HIV-regimen. Methadone-maintained patients should be monitored for evidence of withdrawal and the methadone dose should be adjusted accordingly.
Efavirenz; Lamivudine; Tenofovir Disoproxil Fumarate: (Major) Coadministration of efavirenz and methadone may increase the risk for QT prolongation and torsade de pointes (TdP). QT prolongation has been observed with use of efavirenz. Although data are limited, the manufacturer of efavirenz recommends an alternative antiretroviral be considered for patients receiving medications with a known risk for TdP. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, efavirenz induces methadone metabolism via CYP3A4 and is associated with significant decreases in methadone concentrations. Clinical reports suggest that patients who are stabilized on methadone-maintenance therapy may experience opiate withdrawal symptoms when efavirenz is added to their HIV-regimen. Methadone-maintained patients should be monitored for evidence of withdrawal and the methadone dose should be adjusted accordingly.
Elagolix: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with elagolix is necessary; elagolix may induce methadone metabolism. Consider increasing the dose of methadone if clinically warranted, with consideration of the long half-life of methadone. If elagolix is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a substrate of CYP 3A4 and 2C19. Elagolix is a weak to moderate CYP3A4 inducer and a weak CYP2C19 inhibitor. Concomitant use of methadone with CYP3A4 inducers can decrease methadone levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Elagolix; Estradiol; Norethindrone acetate: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with elagolix is necessary; elagolix may induce methadone metabolism. Consider increasing the dose of methadone if clinically warranted, with consideration of the long half-life of methadone. If elagolix is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a substrate of CYP 3A4 and 2C19. Elagolix is a weak to moderate CYP3A4 inducer and a weak CYP2C19 inhibitor. Concomitant use of methadone with CYP3A4 inducers can decrease methadone levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Eletriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Elexacaftor; tezacaftor; ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as methadone. Ivacaftor is an inhibitor of CYP3A, P-glycoprotein (Pgp), and a weak inhibitor of CYP2C9; methadone is metabolized by CYP3A4, CYP2C9, and is a substrate of Pgp. Co-administration of ivacaftor with CYP3A, CYP2C9, and Pgp substrates,such as methadone may increase methadone exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Eliglustat: (Major) Coadministration of methadone and eliglustat may result in increased opioid plasma concentrations and an increased risk for QT prolongation. If coadministration is necessary, use great caution and monitor patients closely at frequent intervals. Consider reducing the dosage of methadone until stable drug effects are achieved, and titrating to clinical effect. Eliglustat is a CYP2D6 and P-glycoprotein (P-gp) inhibitor that is predicted to cause PR, QRS, and/or QT prolongation at significantly elevated plasma concentrations. Although methadone is primarily metabolized by other CYP450 isoenzymes (i.e., CYP3A4, CYP2B6, CYP2C19), it is metabolized to a lesser extent by CYP2D6 and is considered a P-gp substrate. In addition, methadone is independently associated with a risk for QT prolongation and torsade de pointes (TdP). Coadministration of methadone and eliglustat may result in additive effects on the QT interval and, potentially, increased plasma concentrations of methadone, further increasing the risk of serious adverse events (e.g., respiratory depression, sedation, QT prolongation, cardiac arrhythmias).
Eluxadoline: (Major) Avoid use of eluxadoline with medications that may cause constipation, such as methadone. Opioids increase the tone and decrease the propulsive contractions of the smooth muscle within the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. Closely monitor for increased side effects if these drugs are administered together.
Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Alafenamide: (Moderate) Caution is warranted when elvitegravir is administered with methadone as there is a potential for decreased methadone concentrations and the dosage of methadone may need to be increased. Methadone is partially metabolized by CYP2C9, while elvitegravir is a CYP2C9 inducer. (Moderate) The plasma concentrations of methadone may be elevated when administered concurrently with cobicistat. When initiating methadone in patients currently on a regimen containing cobicistat and atazanavir or darunavir, use the lowest methadone starting dose and slowly titrate to desired effect. When initiating antiretroviral regimens containing cobicistat and atazanavir or darunavir to patients on methadone, an adjustment of methadone dose may be needed. Monitoring for adverse effects, such as CNS side effects or respiratory depression, is recommended during coadministration. Methadone is metabolized primarily by the cytochrome P450 isoenzymes CYP2C19, CYP3A4, and CYP2B6, and to a lesser extent, by CYP2C9 and CYP2D6. Methadone also is a substrate of P-glycoprotein (P-gp). Cobicistat is an inhibitor of CYP3A4, CYP2D6, and P-gp.
Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Disoproxil Fumarate: (Moderate) Caution is warranted when elvitegravir is administered with methadone as there is a potential for decreased methadone concentrations and the dosage of methadone may need to be increased. Methadone is partially metabolized by CYP2C9, while elvitegravir is a CYP2C9 inducer. (Moderate) The plasma concentrations of methadone may be elevated when administered concurrently with cobicistat. When initiating methadone in patients currently on a regimen containing cobicistat and atazanavir or darunavir, use the lowest methadone starting dose and slowly titrate to desired effect. When initiating antiretroviral regimens containing cobicistat and atazanavir or darunavir to patients on methadone, an adjustment of methadone dose may be needed. Monitoring for adverse effects, such as CNS side effects or respiratory depression, is recommended during coadministration. Methadone is metabolized primarily by the cytochrome P450 isoenzymes CYP2C19, CYP3A4, and CYP2B6, and to a lesser extent, by CYP2C9 and CYP2D6. Methadone also is a substrate of P-glycoprotein (P-gp). Cobicistat is an inhibitor of CYP3A4, CYP2D6, and P-gp.
Emtricitabine; Rilpivirine; Tenofovir alafenamide: (Major) Close clinical monitoring is advised with coadministration. Use of these drugs together may cause the plasma concentration of methadone to decrease, thereby resulting in decreased methadone efficacy. No dose adjustments are required when initiating concurrent treatment; however, the maintenance dose of methadone may need to be adjusted in some patients. In addition, due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering rilpivirine with methadone. A careful assessment of treatment risks versus benefits should be conducted prior to coadministration. When initiating concurrent treatment no dose adjustments are required; however, the dose of methadone may need to be adjusted during maintenance therapy. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Supratherapeutic doses of rilpivirine (75 to 300 mg/day) have also been associated with prolongation of the QT interval.
Emtricitabine; Rilpivirine; Tenofovir Disoproxil Fumarate: (Major) Close clinical monitoring is advised with coadministration. Use of these drugs together may cause the plasma concentration of methadone to de crease, thereby resulting in decreased methadone efficacy. No dose adjustments are required when initiating concurrent treatment; however, the maintenance dose of methadone may need to be adjusted in some patients. In addition, due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering rilpivirine with methadone. A careful assessment of treatment risks versus benefits should be conducted prior to coadministration. When initiating concurrent treatment no dose adjustments are required; however, the dose of methadone may need to be adjusted during maintenance therapy. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Supratherapeutic doses of rilpivirine (75 to 300 mg/day) have also been associated with prolongation of the QT interval.
Encorafenib: (Major) Avoid coadministration of encorafenib and methadone due to the potential for additive QT prolongation. If concurrent use cannot be avoided, monitor ECGs for QT prolongation and monitor electrolytes; correct hypokalemia and hypomagnesemia prior to treatment. Encorafenib is associated with dose-dependent prolongation of the QT interval. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Entrectinib: (Major) Avoid coadministration of entrectinib with methadone due to the risk of QT prolongation. Entrectinib has been associated with QT prolongation. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Enzalutamide: (Major) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with enzalutamide is necessary; these effects may be more pronounced with concomitant use of drugs that can induce multiple CYP enzymes. Consider increasing the dose of methadone as needed. If enzalutamide is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a substrate of CYP2C9, CYP2C19, and CYP3A4; enzalutamide is a strong CYP3A4 inducer, as well as a moderate inducer of both CYP2C9 and CYP2C19. Concomitant use with inducers of CYP enzymes can decrease methadone levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Eribulin: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients) Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Drugs with a possible risk for QT prolongation and TdP that should be used cautiously with methadone include eribulin. ECG monitoring is recommended; closely monitor the patient for QT interval prolongation.
Erythromycin: (Major) Due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering erythromycin with methadone. The need to coadminister these drugs should be done with careful assessment of treatment risks versus benefits. Erythromycin is associated with prolongation of the QT interval and TdP. Methadone is also considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses averaging approximately 400 mg/day in adult patients. In addition, methadone is a substrate for CYP3A4 and P-glycoprotein (P-gp), while erythromycin is a CYP3A4 and P-gp inhibitor. Concurrent use may result in increased serum concentrations of methadone.
Escitalopram: (Major) Coadministration may increase the risk of serotonin syndrome, QT prolongation, or torsade de pointes (TdP). Escitalopram has been associated with a risk of QT prolongation and TdP. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, both escitalopram and methadone have central serotonergic properties and serotonin syndrome is possible. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical treatment should be implemented.
Esketamine: (Major) Concomitant use of opioid agonists with esketamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with esketamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Patients who have received a dose of esketamine should be instructed not to drive or engage in other activities requiring complete mental alertness until the next day after a restful sleep. Educate patients about the risks and symptoms of excessive CNS depression.
Estazolam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Eszopiclone: (Moderate) Concomitant use of methadone with eszopiclone can lead to additive respiratory depression, hypotension, profound sedation, or coma. In addition, the risk of next-day psychomotor impairment is increased during co-administration of eszopiclone and other CNS depressants, which may decrease the ability to perform tasks requiring full mental alertness such as driving. Prior to concurrent use, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of eszopiclone. Monitor patients for sedation and respiratory depression.
Ethacrynic Acid: (Moderate) Diuretics can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with diuretics is needed.
Ethanol: (Major) Advise patients to avoid alcohol consumption while taking opioids. Alcohol consumption may result in additive CNS depression and may increase the risk for opioid overdose. Consider the patient's use of alcohol when prescribing opioid medications. If the patient is unlikely to be compliant with avoiding alcohol, consider prescribing naloxone especially if additional risk factors for opioid overdose are present.
Ethotoin: (Moderate) Additive CNS depression including respiratory depression, hypotension, profound sedation, or coma may occur with the combined use of the hydantoin (e.g., phenytoin, fosphenytoin, and ethotoin) and methadone. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. Methadone is a primary substrate for the CYP3A4 isoenzyme. Serum concentrations of methadone may decrease due to CYP3A4 induction by phenytoin, fosphenytoin, and possibly ethotoin; withdrawal symptoms may occur.
Etomidate: (Moderate) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma; examples include general anesthetics. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Etravirine: (Moderate) No methadone dosage adjustments are expected when coadministered with etravirine. However, clinical monitoring for withdrawal symptoms is recommended as methadone maintenance therapy may need to be adjusted in some patients.
Everolimus: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of everolimus is necessary; consider reducing the dose of methadone if clinically appropriate. If everolimus is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 and CYP2D6 substrate; coadministration with weak CYP3A4/2D6 inhibitors like everolimus can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If everolimus is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Fedratinib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of fedratinib is necessary. If fedratinib is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP3A4, CYP2D6, and CYP2C19 substrate, and coadministration with moderate inhibitors of CYP3A4, CYP2D6, and CYP2C19 like fedratinib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If fedratinib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Fenfluramine: (Moderate) Concomitant use of opioid agonists with fenfluramine may cause excessive sedation and somnolence. Limit the use of opioid agonists with fenfluramine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Fenofibric Acid: (Minor) At therapeutic concentrations, fenofibric acid is a weak inhibitor of CYP2C19 and a mild-to-moderate inhibitor of CYP2C9. Concomitant use of fenofibric acid with CYP2C19 and CYP2C9 substrates, such as methadone, has not been formally studied. Fenofibric acid may theoretically increase plasma concentrations of CYP2C19 and CYP2C9 substrates and could lead to toxicity for drugs that have a narrow therapeutic range. Monitor the therapeutic effect of methadone during coadministration with fenofibric acid.
Fentanyl: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Fesoterodine: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when fesoterodine, an anticholinergic drug for overactive bladder is used with opiate agonists. The concomitant use of these drugs together may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. Both agents may also cause drowsiness or blurred vision, and patients should use care in driving or performing other hazardous tasks until the effects of the drugs are known.
Fingolimod: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Drugs with a possible risk for QT prolongation and TdP that should be used cautiously with methadone include fingolimod. Fingolimod initiation results in decreased heart rate and may prolong the QT interval. After the first fingolimod dose, overnight monitoring with continuous ECG in a medical facility is advised for patients taking QT prolonging drugs with a known risk of torsades de pointes (TdP). Fingolimod has not been studied in patients treated with drugs that prolong the QT interval, but drugs that prolong the QT interval have been associated with cases of TdP in patients with bradycardia.
Flecainide: (Major) Concomitant use of methadone and flecainide increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Flibanserin: (Moderate) Concomitant use of opioid agonists with flibanserin may cause excessive sedation and somnolence. Limit the use of opioid pain medication with flibanserin to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Fluconazole: (Major) Administer fluconazole and methadone concomitantly with caution. Both fluconazole and methadone are associated with QT prolongation and torsade de pointes (TdP). Additionally, fluconazole is a CYP3A4, CYP2C19, and CYP2C9 inhibitor and methadone is a CYP3A4, CYP2C19, and CYP2C9 substrate; therefore, increased concentrations of methadone may occur which may result in prolonged duration of action, increased sedation, respiratory depression, QT prolongation, or other side effect. The manufacturer of fluconazole states dosage adjustments of methadone may be necessary during concomitant therapy with fluconazole.
Fludrocortisone: (Moderate) Mineralocorticoid hormones such as fludrocortisone can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with mineralocorticoid hormones is needed.
Fluoxetine: (Major) Coadministration may increase the risk of serotonin syndrome, QT prolongation, torsade de pointes (TdP), or opioid-related side effects. QT prolongation and TdP have been reported in patients treated with fluoxetine and the manufacturer recommends caution when using fluoxetine with other drugs that prolong the QT interval. Methadone is associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, both fluoxetine and methadone have central serotonergic properties and serotonin syndrome is possible. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical treatment should be implemented. Lastly, fluoxetine may inhibit the metabolism of methadone via CYP3A4 or CYP2D6. In patients treated with methadone and fluoxetine, the plasma concentration of methadone increased. Interestingly in patients treated with methadone, the R-enantiomer (the active moiety) was increased by the addition of fluoxetine. Patients may experience increases in CNS depressive effects or respiratory depression. Thus, methadone-treated patients receiving fluoxetine should be carefully monitored and dosage adjustments may be warranted.
Fluphenazine: (Minor) Fluphenazine should be used cautiously and with close monitoring with methadone. Fluphenazine, a phenothiazine, is associated with a possible risk for QT prolongation. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, phenothiazines can potentiate the CNS-depressant action of methadone. Caution should be exercised during simultaneous use of these agents due to potential excessive CNS effects or additive hypotension.
Flurazepam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Fluvoxamine: (Major) Coadministration may increase the risk of serotonin syndrome, QT prolongation, or torsade de pointes (TdP). Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although there are reports in patients receiving doses commonly used for maintenance treatment of opioid addiction. Cases of QT prolongation and TdP have been reported during postmarketing use of fluvoxamine. In addition, both fluvoxamine and methadone have central serotonergic properties and serotonin syndrome is possible. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical treatment should be implemented. Lastly, fluvoxamine is a potent inhibitor of CYP2C19 and a moderate inhibitor of CYP3A4, two of the isoenzymes responsible for the metabolism of methadone. In a small number of patients receiving methadone for opiate dependence, the addition of fluvoxamine produced a substantial increase in methadone serum concentrations. Clinical symptoms of methadone excess have resulted from concurrent use.
Food: (Major) Advise patients to avoid cannabis use while taking CNS depressants due to the risk for additive CNS depression and potential for other cognitive adverse reactions.
Fosamprenavir: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of fosamprenavir is necessary. If fosamprenavir is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; fosamprenavir is a moderate CYP3A inhibitor. Concomitant use with fosamprenavir can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Foscarnet: (Major) When possible, avoid concurrent use of foscarnet with other drugs known to prolong the QT interval, such as methadone. Foscarnet has been associated with postmarketing reports of both QT prolongation and torsade de pointes (TdP). Methadone is also considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. If these drugs are administered together, obtain an electrocardiogram and electrolyte concentrations before and periodically during treatment.
Fosphenytoin: (Moderate) Additive CNS depression including respiratory depression, hypotension, profound sedation, or coma may occur with the combined use of the hydantoin (e.g., phenytoin, fosphenytoin, and ethotoin) and methadone. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. Methadone is a primary substrate for the CYP3A4 isoenzyme. Serum concentrations of methadone may decrease due to CYP3A4 induction by phenytoin, fosphenytoin, and possibly ethotoin; withdrawal symptoms may occur.
Fostamatinib: (Moderate) Monitor for methadone toxicities that may require methadone dose reduction if given concurrently with fostamatinib. Concomitant use of fostamatinib with a CYP3A4 substrate may increase the concentration of the CYP3A4 substrate. The active metabolite of fostamatinib, R406, is a CYP3A4 inhibitor; methadone is a substrate for CYP3A4. Coadministration of fostamatinib with a sensitive CYP3A4 substrate increased the substrate AUC by 64% and Cmax by 113%.
Fostemsavir: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Supratherapeutic doses of fostemsavir (2,400 mg twice daily, four times the recommended daily dose) have been shown to cause QT prolongation. Fostemsavir causes dose-dependent QT prolongation.
Frovatriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Furosemide: (Moderate) Diuretics can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with diuretics is needed.
Gabapentin: (Major) Concomitant use of opioid agonists with gabapentin may cause excessive sedation, somnolence, and respiratory depression. Limit the use of opioid pain medications with gabapentin to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, initiate gabapentin at the lowest recommended dose and monitor patients for symptoms of respiratory depression and sedation. Use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression and respiratory depression.
Gemifloxacin: (Major) The need to coadminister methadone with gemifloxacin should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Gemifloxacin may also prolong the QT interval in some patients, with the maximal change in the QTc interval occurring approximately 5 to 10 hours following oral administration. The likelihood of QTc prolongation may increase with increasing dose of gemifloxacin; therefore, the recommended dose should not be exceeded especially in patients with renal or hepatic impairment where the Cmax and AUC are slightly higher.
Gemtuzumab Ozogamicin: (Major) Use gemtuzumab ozogamicin and methadone together with caution due to the potential for additive QT interval prolongation and risk of torsade de pointes (TdP). If these agents are used together, obtain an ECG and serum electrolytes prior to the start of gemtuzumab and as needed during treatment. Although QT interval prolongation has not been reported with gemtuzumab, it has been reported with other drugs that contain calicheamicin. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Gilteritinib: (Major) Use extreme caution and monitor for additive QT prolongation if concurrent use of gilteritinib and methadone is necessary; carefully assess treatment risks versus benefits. Gilteritinib has been associated with QT prolongation. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Givosiran: (Major) Avoid concomitant use of givosiran and methadone due to the risk of increased methadone-related adverse reactions. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of givosiran is necessary. If givosiran is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate, and coadministration with CYP2D6 inhibitors like givosiran can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If givosiran is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Givosiran may moderately reduce hepatic CYP2D6 enzyme activity because of its pharmacological effects on the hepatic heme biosynthesis pathway. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of celecoxib is necessary. If celecoxib is discontinued, consider increasing the methadone dose until stabilized.
Glasdegib: (Major) Avoid coadministration of glasdegib with methadone due to the potential for additive QT prolongation. If coadministration cannot be avoided, monitor patients for increased risk of QT prolongation with increased frequency of ECG monitoring. Glasdegib therapy may result in QT prolongation and ventricular arrhythmias including ventricular fibrillation and ventricular tachycardia. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Glycerol Phenylbutyrate: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with glycerol phenylbutyrate is necessary. Consider increasing the dose of methadone as needed. If glycerol phenylbutyrate is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; glycerol phenylbutyrate is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Goserelin: (Major) Coadministration of methadone with goserelin should be undertaken with extreme caution and a careful assessment of the benefits of therapy versus the risks of QT prolongation. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy may prolong the QT/QTc interval.
Granisetron: (Major) Because of the potential risk and severity of serotonin syndrome, use caution and monitor closely when administering methadone with other drugs that have serotonergic properties such as granisetron. Serotonin syndrome is characterized by rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If serotonin syndrome is suspected, discontinue granisetron and concurrent serotonergic agents and initiate appropriate medical treatment. In addition, methadone is associated with a risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Therefore, methadone should be used cautiously with drugs having a possible risk for QT prolongation and torsade de pointes (TdP) such as granisetron.
Grapefruit juice: (Moderate) The concurrent administration of methadone and inhibitors of CYP3A4, such as grapefruit juice, may result in increased concentrations of methadone. Inhibition of methadone metabolism can lead to toxicity including CNS adverse effects and potential for QT prolongation and torsades de pointes when high doses of methadone are used.
Guaifenesin; Hydrocodone: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Guanfacine: (Moderate) Concomitant use of opioid agonists with guanfacine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with guanfacine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Guselkumab: (Moderate) Clinically relevant drug interactions may occur when guselkumab is administered with sensitive substrates of CYP2D6, such as methadone. Monitor methadone concentrations if guselkumab is initiated or discontinued; the methadone dose may need to be adjusted. During chronic inflammation, increased levels of certain cytokines can alter the formation of CYP450 enzymes. Thus, the formation of CYP2D6 could be normalized during guselkumab administration.
Haloperidol: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with inhibitors of these enzymes may result in increased serum concentrations of methadone. Drugs with a possible risk for QT prolongation and TdP that inhibit CYP2D6 include haloperidol. Concomitant use of methadone with another CNS depressant, such as haloperidol, can also lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Histrelin: (Major) Coadministration of methadone with histrelin should be undertaken with extreme caution and a careful assessment of the benefits of therapy versus the risks of QT prolongation. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy may prolong the QT/QTc interval.
Homatropine; Hydrocodone: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Hydantoins: (Moderate) Additive CNS depression including respiratory depression, hypotension, profound sedation, or coma may occur with the combined use of the hydantoin (e.g., phenytoin, fosphenytoin, and ethotoin) and methadone. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. Methadone is a primary substrate for the CYP3A4 isoenzyme. Serum concentrations of methadone may decrease due to CYP3A4 induction by phenytoin, fosphenytoin, and possibly ethotoin; withdrawal symptoms may occur.
Hydrochlorothiazide, HCTZ; Methyldopa: (Moderate) Concomitant use of opioid agonists with methyldopa may cause excessive sedation and somnolence. Limit the use of opioid pain medication with methyldopa to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Hydrocodone: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Hydrocodone; Ibuprofen: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Hydrocodone; Pseudoephedrine: (Major) Concomitant use of hydrocodone with other CNS depressants may lead to hypotension, profound sedation, coma, respiratory depression and death. Prior to concurrent use of hydrocodone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Hydrocodone should be used in reduced dosages if used concurrently with a CNS depressant; initiate hydrocodone at 20 to 30% of the usual dosage in patients that are concurrently receiving another CNS depressant. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Hydromorphone: (Major) Concomitant use of hydromorphone with other central nervous system (CNS) depressants, such as other opiate agonists, can potentiate the effects of hydromorphone and may lead to additive CNS or respiratory depression, profound sedation, or coma. Prior to concurrent use of hydromorphone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. If hydromorphone is used concurrently with a CNS depressant, a reduced dosage of hydromorphone and/or the CNS depressant is recommended; start with one-third to one-half of the estimated hydromorphone starting dose when using hydromorphone extended-release tablets. Carefully monitor the patient for hypotension, CNS depression, and respiratory depression. Carbon dioxide retention from opioid-induced respiratory depression can exacerbate the sedating effects of opioids.
Hydroxychloroquine: (Major) Concomitant use of methadone and hydroxychloroquine increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Hydroxyzine: (Major) Hydroxyzine should be used cautiously and with close monitoring with methadone due to the potential for increased risk of QT prolongation, torsade de pointes (TdP), and additive CNS depressant effects. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression and QT prolongation. Post-marketing data indicate that hydroxyzine causes QT prolongation and TdP. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Hyoscyamine; Methenamine; Methylene Blue; Phenyl Salicylate; Sodium Biphosphate: (Major) Avoid concomitant use of methadone in patients receiving methylene blue or within 14 days of stopping treatment with methylene blue due to the risk of serotonin syndrome or opioid toxicity, including respiratory depression. If cannot avoid use, choose the lowest possible methylene blue dose and observe the patient closely for up to 4 hours after administration. (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Ibritumomab Tiuxetan: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Ibuprofen; Oxycodone: (Major) Concomitant use of methadone with another CNS depressant, such as oxycodone, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also, consider a using a lower dose of the CNS depressant; use an initial dose of oxycodone at one-third to one-half the usual dosage. Monitor patients for sedation and respiratory depression.
Ibutilide: (Major) Ibutilide administration can cause QT prolongation and torsades de pointes (TdP); proarrhythmic events should be anticipated. The potential for proarrhythmic events with ibutilide increases with the coadministration of other drugs that prolong the QT interval, such as methadone. The need to coadminister methadone with ibutilide should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Idelalisib: (Major) Avoid concomitant use of idelalisib, a strong CYP3A inhibitor, with methadone, a CYP3A substrate, as methadone toxicities may be significantly increased. The AUC of a sensitive CYP3A substrate was increased 5.4-fold when coadministered with idelalisib.
Iloperidone: (Major) Iloperidone has been associated with QT prolongation; however, torsade de pointes (TdP) has not been reported. According to the manufacturer, since iloperidone may prolong the QT interval, it should be avoided in combination with other agents also known to have this effect, such as methadone. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Additive CNS depression is also possible.
Imatinib: (Moderate) The concurrent administration of methadone and inhibitors of cytochrome P450 3A4, such as imatinib, may result in increased concentrations of methadone. Inhibition of methadone metabolism can lead to toxicity including CNS adverse effects and potential for QT prolongation and torsades de pointes when high doses of methadone are used.
Imipramine: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Indinavir: (Moderate) Caution is advised with the coadministration of indinavir and methadone as concurrent use may result in incresed serum concentrations of methadone. Indinavir is a CYP3A4 inhibitor and may decrease the metabolism of methadone, a CYP3A4 substrate. However, administration of indinavir (800 mg every 8 hours) with methadone (2060 mg daily) for one week, in subjects on methadone maintenance, resulted in no change in methadone AUC. Based on a comparison to historical data, there was little or no change in indinavir AUC. Patients should be monitored for increased methadone side effects during concurrent use.
Inotuzumab Ozogamicin: (Major) Avoid coadministration of inotuzumab ozogamicin with methadone due to the potential for additive QT prolongation and risk of torsade de pointes (TdP). If coadministration is unavoidable, obtain an ECG and serum electrolytes prior to the start of treatment, after treatment initiation, and periodically during treatment. Inotuzumab has been associated with QT interval prolongation. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Isavuconazonium: (Moderate) Concomitant use of isavuconazonium with methadone may result in increased serum concentrations of methadone. Methadone is a substrate of the hepatic isoenzyme CYP3A4; isavuconazole, the active moiety of isavuconazonium, is a moderate inhibitor of this enzyme. Caution and close monitoring are advised if these drugs are used together.
Isocarboxazid: (Major) Coadministration of methadone with monoamine oxidase inhibitors (MAOIs) or within 14 days after discontinuation of treatment with an MAOI is not recommended due to the risk of serotonin syndrome and/or respiratory depression.
Isoflurane: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Halogenated anesthetics can prolong the QT interval. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Major) Concurrent administration of rifampin and methadone is associated with a 33 to 68% decrease in methadone levels due to induction of methadone metabolism by rifampin. When effective alternatives exist, rifampin should not be administered to patients receiving chronic methadone therapy. However, if rifampin treatment is necessary, the methadone dosage will need to be increased to maintain adequate suppression of opiate withdrawal symptoms.
Isoniazid, INH; Rifampin: (Major) Concurrent administration of rifampin and methadone is associated with a 33 to 68% decrease in methadone levels due to induction of methadone metabolism by rifampin. When effective alternatives exist, rifampin should not be administered to patients receiving chronic methadone therapy. However, if rifampin treatment is necessary, the methadone dosage will need to be increased to maintain adequate suppression of opiate withdrawal symptoms.
Istradefylline: (Moderate) Concomitant use of methadone with istradefylline 40 mg daily may increase methadone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of methadone until stable drug effects are achieved. Discontinuation of istradefylline could decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to methadone. If istradefylline is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Methadone is a substrate for CYP3A4; istradefylline administered as 40 mg daily is a weak CYP3A4 inhibitor. There was no effect on drug exposure when istradefylline 20 mg daily was coadministered with a sensitive CYP3A4 substrate.
Itraconazole: (Contraindicated) Methadone is contraindicated for use during and for 2 weeks after itraconazole therapy. Serious cardiovascular events including EKG changes (i.e., QT prolongation) and cardiac arrhythmias, including ventricular arrhythmias and torsade de pointes, cardiac arrest, and/or sudden death have occurred when these drugs were administered together. Methadone is a CYP3A4 substrate; itraconazole is a strong CYP3A4 inhibitor.
Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as methadone. Ivacaftor is an inhibitor of CYP3A, P-glycoprotein (Pgp), and a weak inhibitor of CYP2C9; methadone is metabolized by CYP3A4, CYP2C9, and is a substrate of Pgp. Co-administration of ivacaftor with CYP3A, CYP2C9, and Pgp substrates,such as methadone may increase methadone exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Ivosidenib: (Major) Avoid coadministration of ivosidenib with methadone due to an increased risk of QT prolongation. If concomitant use is unavoidable, monitor ECGs for QTc prolongation and monitor electrolytes; correct any electrolyte abnormalities as clinically appropriate. An interruption of therapy and dose reduction of ivosidenib may be necessary if QT prolongation occurs. Prolongation of the QTc interval and ventricular arrhythmias have been reported in patients treated with ivosidenib. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Ketamine: (Moderate) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma; examples include general anesthetics. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Ketoconazole: (Contraindicated) Avoid concomitant use of ketoconazole and methadone due to an increased risk for torsade de pointes (TdP) and QT/QTc prolongation. Concomitant use may also increase the exposure of methadone, further increasing the risk for adverse effects, such as respiratory and/or CNS depression. Methadone is a CYP3A4 substrate and ketoconazole is a strong CYP3A inhibitor.
Lamivudine, 3TC; Zidovudine, ZDV: (Moderate) Methadone increases exposure zidovudine, ZDV. Patients should be monitored for zidovudine toxicity during concurrent methadone treatment; however, the manufacturer of zidovudine states t hat routine dosage adjustment of zidovudine is not required during coadministration of methadone. Patients who receive both methadone and zidovudine may experience symptoms characteristic of opiate withdrawal and attribute the cause to decreased methadone levels due to zidovudine. However, it is more likely patients are actually experiencing zidovudine side effects due to increased levels since zidovudine has no effect on methadone metabolism. In one pharmacokinetic study (n=9), coadministration of methadone increased the AUC of zidovudine by about 43% (range: 16-64%). It appears methadone inhibits zidovudine glucuronidation and, to a lesser extent, decreases zidovudine renal clearance.
Lansoprazole; Amoxicillin; Clarithromycin: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as clarithromycin, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with clarithromycin, an inhibitor of CYP3A4 and P-gp, may result in increased serum concentrations of methadone.
Lapatinib: (Major) Carefully assess treatment risks versus benefits if coadministration of methadone with lapatinib is necessary due to the risk of QT prolongation and increased methadone exposure. Monitor ECGs for QT prolongation and monitor electrolytes if coadministration is necessary; correct electrolyte abnormalities prior to treatment. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation. If lapatinib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone; consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP3A4 substrate, and coadministration with weak CYP3A4 inhibitors like lapatinib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. Methadone is also associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Lapatinib has also been associated with concentration-dependent QT prolongation; ventricular arrhythmias and TdP have been reported in postmarketing experience with lapatinib.
Larotrectinib: (Moderate) Concomitant use of methadone with larotrectinib may increase methadone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of methadone until stable drug effects are achieved. Discontinuation of larotrectinib could decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to methadone. If larotrectinib is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Methadone is a substrate for CYP3A4. Larotrectinib is a weak inhibitor of CYP3A4.
Lasmiditan: (Moderate) Concomitant use of methadone with lasmiditan may cause excessive sedation, somnolence, and serotonin syndrome. Limit the use of methadone with lasmiditan to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression and serotonin syndrome.
Ledipasvir; Sofosbuvir: (Moderate) Caution and close monitoring of methadone-associated adverse reactions is advised with concomitant administration of ledipasvir. Methadone is a substrate of the drug transporter P-glycoprotein (P-gp); ledipasvir is a P-gp inhibitor. Taking these drugs together may increase methadone plasma concentrations.
Lefamulin: (Major) Avoid coadministration of lefamulin with methadone as concurrent use may increase the risk of QT prolongation; use of oral lefamulin may increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If coadministration cannot be avoided, monitor ECG during treatment. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of oral lefamulin is necessary. Lefamulin has a concentration dependent QTc prolongation effect; oral lefamulin is a moderate CYP3A4 inhibitor. The pharmacodynamic interaction potential to prolong the QT interval of the electrocardiogram between lefamulin and other drugs that effect cardiac conduction is unknown. Methadone is a CYP3A4 substrate considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Lemborexant: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with lemborexant is necessary. Consider increasing the dose of methadone as needed. Also monitor for additive CNS effects. If lemborexant is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; lemborexant is a weak CYP2B6 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Lenacapavir: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of lenacapavir is necessary. If lenacapavir is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; lenacapavir is a moderate CYP3A inhibitor. Concomitant use with lenacapavir can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Lenvatinib: (Major) Avoid coadministration of lenvatinib with methadone due to the risk of QT prolongation. Prolongation of the QT interval has been reported with lenvatinib therapy. Methadone is also considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Letermovir: (Moderate) Plasma concentrations of methadone could be altered (increased or decreased) when administered concurrently with letermovir. In patients who are also receiving cyclosporine, the impact on the increase in methadone exposure may be increased. If these drugs are given together, closely monitor for reduced methadone efficacy and methadone-related adverse events. Consider a methadone dose increase if the patient shows signs or symptoms of opioid withdrawal. Conversely, consider reducing the methadone dose if patient show signs of respiratory depression or sedation. Methadone is a substrate of the enzymes CYP3A4, CYP2C9, and CYP2C19. Letermovir is an inducer of CYP2C9 and CYP2C19, and a moderate inhibitor of CYP3A4. When given with cyclosporine, the combined effect of letermovir and cyclosporine on CYP3A4 substrates may be similar to a strong CYP3A4 inhibitor.
Leuprolide: (Major) Coadministration of methadone with leuprolide should be undertaken with extreme caution and a careful assessment of the benefits of therapy versus the risks of QT prolongation. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy may prolong the QT/QTc interval.
Leuprolide; Norethindrone: (Major) Coadministration of methadone with leuprolide should be undertaken with extreme caution and a careful assessment of the benefits of therapy versus the risks of QT prolongation. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy may prolong the QT/QTc interval.
Levamlodipine: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Levocetirizine: (Major) Reserve concomitant use of opioids and cetirizine for patients in whom alternate treatment options are inadequate. Limit dosages and durations to the minimum required and monitor patients closely for respiratory depression and sedation. If concomitant use is necessary, consider prescribing naloxone for the emergency treatment of opioid overdose and monitor for signs of urinary retention or reduced gastric motility. Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe constipation, which may lead to paralytic ileus.
Levofloxacin: (Major) Concomitant use of levofloxacin and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Levoketoconazole: (Contraindicated) Avoid concomitant use of ketoconazole and methadone due to an increased risk for torsade de pointes (TdP) and QT/QTc prolongation. Concomitant use may also increase the exposure of methadone, further increasing the risk for adverse effects, such as respiratory and/or CNS depression. Methadone is a CYP3A4 substrate and ketoconazole is a strong CYP3A inhibitor.
Levomilnacipran: (Moderate) If concomitant use of methadone and levomilnacipran is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Levorphanol: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Lidocaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Lidocaine; Epinephrine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Lidocaine; Prilocaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Linezolid: (Major) Avoid concomitant use of methadone in patients receiving linezolid or within 14 days of stopping treatment with linezolid due to the risk of serotonin syndrome or opioid toxicity, including respiratory depression.
Lisdexamfetamine: (Moderate) If concomitant use of methadone and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Lithium: (Major) Concomitant use of lithium and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Lofexidine: (Major) Monitor ECG if lofexidine is coadministered with methadone due to the potential for additive QT prolongation and torsade de pointes (TdP). Additionally, monitor for excessive hypotension and sedation during coadministration as lofexidine can potentiate the effects of CNS depressants. Lofexidine prolongs the QT interval. In addition, there are postmarketing reports of TdP. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In electrophysiology studies, lofexidine (2.88 mg/day) coadministered with methadone (80 to 120 mg/day) resulted in a maximum mean QTcF increase of 9.1 (14.2) msec from methadone-alone baseline.
Lonafarnib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of lonafarnib is necessary. If lonafarnib is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; lonafarnib is a strong CYP3A4 and moderate CYP2C19 inhibitor. Concomitant use with lonafarnib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Loop diuretics: (Moderate) Diuretics can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with diuretics is needed.
Loperamide: (Major) Concomitant use of loperamide and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Loperamide; Simethicone: (Major) Concomitant use of loperamide and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Lopinavir; Ritonavir: (Major) Avoid coadministration of lopinavir with methadone due to the potential for additive QT prolongation. If use together is necessary, obtain a baseline ECG to assess initial QT interval and determine frequency of subsequent ECG monitoring, avoid any non-essential QT prolonging drugs, and correct electrolyte imbalances. Lopinavir is associated with QT prolongation. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. (Moderate) Coadministration of ritonavir with methadone has resulted in decreased methadone plasma concentrations. However, because methadone is metabolized by multiple CYP450 enzymes, including CYP3A4, CYP2C19, CYP2C9, and CYP2D6, and ritonavir is known to inhibit CYP3A4 and CYP2D6 and induce CYP2C19 and CYP2C9, the potential for increased methadone exposure should also be considered with concomitant administration. Therefore, concurrent use may increase or prolong opioid effects, resulting in fatal overdose or may decrease methadone efficacy or produce onset of withdrawal symptoms in patients physically dependent on methadone. Monitor for respiratory depression, sedation, and signs of opioid withdrawal. Consider adjusting the methadone dose until stable drug effects are achieved. If ritonavir is discontinued, and its CYP450 effects decline, methadone plasma concentrations may increase or decrease. Closely monitor for increased opioid adverse effects and for evidence of withdrawal and adjust the methadone dose as necessary when ritonavir is discontinued.
Lorazepam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Lorcaserin: (Moderate) Monitor patients for respiratory depression and sedation at frequent intervals if concomitant administration of methadone and lorcaserin is necessary; consider reducing the methadone dose until stable effects are achieved. Concomitant use of methadone and lorcaserin may increase the plasma concentration of methadone, resulting in increased or prolonged opioid effects. If lorcaserin is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate and lorcaserin is a CYP2D6 inhibitor. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Lorlatinib: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with lorlatinib is necessary; these effects may be more pronounced with concomitant use of drugs that can induce multiple CYP enzymes. Consider increasing the dose of methadone as needed. If lorlatinib is discontinued, consider a dose reduction of methadone and frequently monitor for signs or respiratory depression and sedation. Methadone is a substrate of CYP2C9, CYP2C19, and CYP3A4; lorlatinib is a moderate CYP3A4 inducer. Concomitant use with CYP3A4 inducers can decrease methadone levels; this may result in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Loxapine: (Moderate) Concomitant use of opioid agonists, such as methadone, with loxapine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with loxapine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Lubiprostone: (Major) Non-clinical studies have shown that opioids of the diphenylheptane chemical class (e.g., methadone) dose-dependently reduce the activation of ClC-2 by lubiprostone in the gastrointestinal tract. There is a possibility of a dose-dependent decrease in the efficacy of lubiprostone in patients using diphenylheptane opioids. Effectiveness in the treatment of opioid-induced constipation in patients taking diphenylheptane opioids (e.g., methadone) has not been established; patients taking methadone during clinical trials for opioid induced constipation had lower response rates than placebo-treated patients.
Luliconazole: (Moderate) Theoretically, luliconazole may increase the side effects of methadone, which is a CYP2C19 and a CYP3A4 substrate. Monitor patients for adverse effects of methadone, such as CNS and respiratory depression. In vitro, therapeutic doses of luliconazole inhibit the activity of CYP2C19 and CYP3A4 and small systemic concentrations may be noted with topical application, particularly when applied to patients with moderate to severe tinea cruris. No in vivo drug interaction trials were conducted prior to the approval of luliconazole.
Lumacaftor; Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as methadone. Ivacaftor is an inhibitor of CYP3A, P-glycoprotein (Pgp), and a weak inhibitor of CYP2C9; methadone is metabolized by CYP3A4, CYP2C9, and is a substrate of Pgp. Co-administration of ivacaftor with CYP3A, CYP2C9, and Pgp substrates,such as methadone may increase methadone exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined. (Moderate) Lumacaftor; ivacaftor may reduce the efficacy of methadone by decreasing its systemic exposure. If used together, monitor patients closely for loss of methadone efficacy; a methadone dosage adjustment may be required to obtain the desired therapeutic effect. Methadone is a substrate of CYP3A4 (primary), CYP2B6, CYP2C9, and CYP2C19. Lumacaftor is a strong CYP3A inducer; in vitro data also suggest that lumacaftor may induce CYP2B6 and CYP2C19 and induce and/or inhibit CYP2C9.
Lumacaftor; Ivacaftor: (Moderate) Lumacaftor; ivacaftor may reduce the efficacy of methadone by decreasing its systemic exposure. If used together, monitor patients closely for loss of methadone efficacy; a methadone dosage adjustment may be required to obtain the desired therapeutic effect. Methadone is a substrate of CYP3A4 (primary), CYP2B6, CYP2C9, and CYP2C19. Lumacaftor is a strong CYP3A inducer; in vitro data also suggest that lumacaftor may induce CYP2B6 and CYP2C19 and induce and/or inhibit CYP2C9.
Lumateperone: (Moderate) Concomitant use of opioid agonists like methadone with lumateperone may cause excessive sedation and somnolence. Limit the use of opioid pain medication with lumateperone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Lurasidone: (Moderate) Concomitant use of opioid agonists like methadone with lurasidone may cause excessive sedation and somnolence. Limit the use of opioid pain medication with lurasidone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Macimorelin: (Major) Avoid concurrent administration of macimorelin with drugs that prolong the QT interval, such as methadone. Use of these drugs together may increase the risk of developing torsade de pointes-type ventricular tachycardia. Sufficient washout time of drugs that are known to prolong the QT interval prior to administration of macimorelin is recommended. Treatment with macimorelin has been associated with an increase in the corrected QT (QTc) interval. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Maprotiline: (Major) Concomitant use of opioid agonists with maprotiline may cause excessive sedation and somnolence. Limit the use of opioid pain medications with maprotiline to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Maribavir: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of maribavir is necessary. If maribavir is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A; maribavir is a weak CYP3A inhibitor. Concomitant use with maribavir can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Mavacamten: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with mavacamten is necessary. Consider increasing the dose of methadone as needed. If mavacamten is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; mavacamten is a moderate CYPC29, CYP2C19, and CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Meclizine: (Moderate) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma; examples include sedating H1-blockers. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Mefloquine: (Major) Due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering methadone with mefloquine. The need to coadminister these drugs should be done with extreme caution and a careful assessment of treatment risks versus benefits. There is evidence that the use of halofantrine after mefloquine causes significant lengthening of the QTc interval. Mefloquine alone has not been reported to cause QT prolongation; however due to the lack of clinical data, mefloquine should be used with caution in patients receiving drugs that prolong the QT interval. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for P-glycoprotein (P-gp), while mefloquine is a P-gp substrate/inhibitor. Coadministration may result in increased serum concentrations of methadone.
Melatonin: (Moderate) Concomitant use of opioid agonists with melatonin may cause excessive sedation and somnolence. Limit the use of opioid pain medications with melatonin to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Meperidine: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Mepivacaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Meprobamate: (Moderate) Concomitant use of methadone with meprobamate can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of meprobamate. Monitor patients for sedation and respiratory depression.
Metaxalone: (Major) Concomitant use of opioid agonists with metaxalone may cause respiratory depression, profound sedation, and death. Limit the use of opioid pain medication with metaxalone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Consider prescribing naloxone for the emergency treatment of opioid overdose. Concomitant use of metaxalone and opioid agonists increases the risk for serotonin syndrome. Avoid concomitant use if possible and monitor for serotonin syndrome if use is necessary.
Methamphetamine: (Moderate) If concomitant use of methadone and amphetamines is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Methenamine; Sodium Acid Phosphate: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Methenamine; Sodium Acid Phosphate; Methylene Blue; Hyoscyamine: (Major) Avoid concomitant use of methadone in patients receiving methylene blue or within 14 days of stopping treatment with methylene blue due to the risk of serotonin syndrome or opioid toxicity, including respiratory depression. If cannot avoid use, choose the lowest possible methylene blue dose and observe the patient closely for up to 4 hours after administration. (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Methocarbamol: (Major) Concomitant use of methadone with a skeletal muscle relaxant may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a skeletal muscle relaxant to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Methohexital: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Methyldopa: (Moderate) Concomitant use of opioid agonists with methyldopa may cause excessive sedation and somnolence. Limit the use of opioid pain medication with methyldopa to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Methylene Blue: (Major) Avoid concomitant use of methadone in patients receiving methylene blue or within 14 days of stopping treatment with methylene blue due to the risk of serotonin syndrome or opioid toxicity, including respiratory depression. If cannot avoid use, choose the lowest possible methylene blue dose and observe the patient closely for up to 4 hours after administration.
Methylphenidate Derivatives: (Moderate) If concomitant use of methadone and methylphenidate derivatives is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Metoclopramide: (Moderate) The effects of metoclopramide on gastrointestinal motility are antagonized by narcotic analgesics. Concomitant use of opioid agonists with metoclopramide may also cause excessive sedation and somnolence. Limit the use of opioid pain medications with metoclopramide to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Metronidazole: (Major) Concomitant use of metronidazole and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Metyrosine: (Moderate) The concomitant administration of metyrosine with opiate agonists can result in additive sedative effects.
Midazolam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Midostaurin: (Major) Concomitant use of midostaurin and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary. Also monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with midostaurin is necessary. Consider increasing the dose of methadone as needed. If midostaurin is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; midostaurin is a weak CYP2B6 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Mifepristone: (Major) Avoid use together if possible. Coadministration of mifepristone may lead to a significant increase in serum concentrations of methadone. The increase in methadone concentrations can increase the risk for serious CNS and respiratory depression or QT prolongation, particularly when mifepristone is added after a stable dose of methadone is achieved. Methadone is a substrate for CYP3A4, CYP2B6, and P-glycoprotein (P-gp). Mifepristone, when used chronically for hormonal conditions such as Cushing's disease, inhibits CYP3A4, 2B6 and may inhibit P-gp. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Mifepristone use is also associated with QT prolongation; to minimize this risk, the lowest effective dose of mifepristone should always be used. Use of these drugs together may increase the risk for QT prolongation. Due to the slow elimination of mifepristone from the body, such interactions may be observed for a prolonged period after mifepristone administration.
Milnacipran: (Moderate) If concomitant use of methadone and milnacipran is warranted, monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Minocycline: (Minor) Injectable minocycline contains magnesium sulfate heptahydrate. Because of the CNS-depressant effects of magnesium sulfate, additive central-depressant effects can occur following concurrent administration with CNS depressants such as opiate agonists. Caution should be exercised when using these agents concurrently.
Mirabegron: (Moderate) Concurrent use of methadone with mirabegron may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Monitor closely until stable drug effects are achieved. Monitor patients for respiratory depression and sedation at frequent intervals. Methadone is a substrate for CYP3A4 and CYP2D6. Mirabegron is a moderate inhibitor of CYP2D6. Discontinuation of mirabegron in a patient taking methadone chronically may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. If mirabegron is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate.
Mirtazapine: (Major) Concomitant use of opioid agonists with mirtazapine may cause excessive sedation and somnolence. Limit the use of opioid pain medications with mirtazapine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Mitapivat: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with mitapivat is necessary. Consider increasing the dose of methadone as needed. If mitapivat is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, and CYP2C9; mitapivat is a weak CYP3A, CYP2B6, and CYP2C9 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Mitotane: (Major) Use caution if mitotane and methadone are used concomitantly, and monitor for decreased efficacy of methadone and a possible change in dosage requirements. Mitotane is a strong CYP3A4 inducer and methadone is a CYP3A4 substrate; coadministration may result in decreased plasma concentrations of methadone. Concurrent administration of another strong CYP3A inducer, rifampin, and methadone is associated with a 33 to 68% decrease in methadone levels due to induction of methadone metabolism by rifampin.
Mobocertinib: (Major) Concomitant use of mobocertinib and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary. Additionally, monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with mobocertinib is necessary. Consider increasing the dose of methadone as needed. If mobocertinib is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; mobocertinib is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Molindone: (Moderate) Concomitant use of opioid agonists like methadone with molindone may cause excessive sedation and somnolence. Limit the use of opioid pain medication with molindone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Monoamine oxidase inhibitors: (Major) Coadministration of methadone with monoamine oxidase inhibitors (MAOIs) or within 14 days after discontinuation of treatment with an MAOI is not recommended due to the risk of serotonin syndrome and/or respiratory depression.
Morphine: (Major) Concomitant use of morphine with methadone can potentiate the effects of both drugs on respiration, blood pressure, and alertness. Profound sedation and coma may also occur. Prior to concurrent use, assess the level of tolerance to CNS depression that has developed and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. A reduced dosage of morphine and/or methadone is recommended; for extended-release products, start with the lowest possible dose of morphine (i.e., 15 mg PO every 12 hours, extended-release tablets; 30 mg or less PO every 24 hours; extended-release capsules). Monitor patients for sedation and respiratory depression.
Morphine; Naltrexone: (Major) Concomitant use of morphine with methadone can potentiate the effects of both drugs on respiration, blood pressure, and alertness. Profound sedation and coma may also occur. Prior to concurrent use, assess the level of tolerance to CNS depression that has developed and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. A reduced dosage of morphine and/or methadone is recommended; for extended-release products, start with the lowest possible dose of morphine (i.e., 15 mg PO every 12 hours, extended-release tablets; 30 mg or less PO every 24 hours; extended-release capsules). Monitor patients for sedation and respiratory depression.
Moxifloxacin: (Major) Concurrent use of methadone and moxifloxacin should be avoided due to an increased risk for QT prolongation and torsade de pointes (TdP). Moxifloxacin has been associated with prolongation of the QT interval. Additionally, post-marketing surveillance has identified very rare cases of ventricular arrhythmias including TdP, usually in patients with severe underlying proarrhythmic conditions. The likelihood of QT prolongation may increase with increasing concentrations of moxifloxacin, therefore the recommended dose or infusion rate should not be exceeded. Methadone is also associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Nabilone: (Major) Avoid coadministration of opioid agonists with nabilone due to the risk of additive CNS depression.
Nalbuphine: (Major) Avoid the concomitant use of nalbuphine and opiate agonists, such as methadone. Nalbuphine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Nalbuphine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of nalbuphine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
Naltrexone: (Major) When naltrexone is used as adjuvant treatment of opiate or alcohol dependence, use is contraindicated in patients currently receiving opiate agonists. Naltrexone will antagonize the therapeutic benefits of opiate agonists and will induce a withdrawal reaction in patients with physical dependence to opioids. Also, patients should be opiate-free for at least 7-10 days prior to initiating naltrexone therapy. If there is any question of opioid use in the past 7-10 days and the patient is not experiencing opioid withdrawal symptoms and/or the urine is negative for opioids, a naloxone challenge test needs to be performed. If a patient receives naltrexone, and an opiate agonist is needed for an emergency situation, large doses of opiate agonists may ultimately overwhelm naltrexone antagonism of opiate receptors. Immediately following administration of exogenous opiate agonists, the opiate plasma concentration may be sufficient to overcome naltrexone competitive blockade, but the patient may experience deeper and more prolonged respiratory depression and thus, may be in danger of respiratory arrest and circulatory collapse. Non-receptor mediated actions like facial swelling, itching, generalized erythema, or bronchoconstriction may occur presumably due to histamine release. A rapidly acting opiate agonist is preferred as the duration of respiratory depression will be shorter. Patients receiving naltrexone may also experience opiate side effects with low doses of opiate agonists. If the opiate agonist is taken in such a way that high concentrations remain in the body beyond the time naltrexone exerts its therapeutic effects, serious side effects may occur.
Naratriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Nefazodone: (Major) Concomitant use of methadone with nefazodone may cause excessive sedation and somnolence. Limit the use of methadone with nefazodone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Monitor patients closely for respiratory depression and sedation at frequent intervals and base subsequent doses on the patient's severity of pain and response to treatment if concomitant administration of methadone and nefazodone is necessary; less frequent dosing of methadone may be required. Concomitant use of methadone and nefazodone may increase the plasma concentration of methadone, resulting in increased or prolonged opioid effects. If nefazodone is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP3A4 substrate and nefazodone is a strong CYP3A4 inhibitor. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Nelfinavir: (Moderate) Nelfinavir decreases methadone concentrations and the dose of methadone may need to be increased. Monitor patient response and titrate the methadone dose as needed.
Nesiritide, BNP: (Major) The potential for hypotension may be increased when coadministering nesiritide with opiate agonists.
Nevirapine: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with nevirapine is necessary. Consider increasing the dose of methadone as needed. If nevirapine is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; nevirapine is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Nicardipine: (Moderate) Nicardipine, a CYP3A4 inhibitor can theoretically inhibit hepatic metabolism of some opiate agonists, CYP3A4 substrates, such as methadone.
Nilotinib: (Major) Avoid coadministration of nilotinib with methadone due to an increased risk for QT prolongation and torsade de pointes (TdP). Systemic exposure of methadone may also be increased resulting in an increase in methadone-related adverse reactions including respiratory depression and sedation. Nilotinib is a moderate CYP3A4 inhibitor; sudden death and QT interval prolongation have occurred in patients who received nilotinib therapy. Methadone is a CYP3A4 substrate that has also been associated with an increased risk of QT prolongation and TdP, especially at higher doses (greater than 200 mg per day but averaging approximately 400 mg per day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Niraparib; Abiraterone: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of abiraterone is necessary. If abiraterone is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate, and coadministration with CYP2D6 inhibitors like abiraterone can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If abiraterone is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Nirmatrelvir; Ritonavir: (Moderate) Coadministration of ritonavir with methadone has resulted in decreased methadone plasma concentrations. However, because methadone is metabolized by multiple CYP450 enzymes, including CYP3A4, CYP2C19, CYP2C9, and CYP2D6, and ritonavir is known to inhibit CYP3A4 and CYP2D6 and induce CYP2C19 and CYP2C9, the potential for increased methadone exposure should also be considered with concomitant administration. Therefore, concurrent use may increase or prolong opioid effects, resulting in fatal overdose or may decrease methadone efficacy or produce onset of withdrawal symptoms in patients physically dependent on methadone. Monitor for respiratory depression, sedation, and signs of opioid withdrawal. Consider adjusting the methadone dose until stable drug effects are achieved. If ritonavir is discontinued, and its CYP450 effects decline, methadone plasma concentrations may increase or decrease. Closely monitor for increased opioid adverse effects and for evidence of withdrawal and adjust the methadone dose as necessary when ritonavir is discontinued.
Nitisinone: (Moderate) Monitor for increased methadone-related adverse effects including excessive sedation and somnolence if coadministered with nitisinone. Increased methadone exposure is possible. Methadone is a CYP2C9 substrate. In vitro data predicts inhibition of CYP2C9 by nitisinone potentially resulting in clinically significant interactions.
Nitroglycerin: (Minor) Nitroglycerin can cause hypotension. This action may be additive with other agents that can cause hypotension such as opiate agonists. Patients should be monitored more closely for hypotension if nitroglycerin is used concurrently with opiate agonists.
Nortriptyline: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT p rolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Odevixibat: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with odevixibat is necessary. Consider increasing the dose of methadone as needed. If odevixibat is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; odevixibat is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Ofloxacin: (Major) Concomitant use of ofloxacin and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Olanzapine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as olanzapine, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, concomitant use of methadone with another CNS depressant, such as olanzapine, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Olanzapine; Fluoxetine: (Major) Coadministration may increase the risk of serotonin syndrome, QT prolongation, torsade de pointes (TdP), or opioid-related side effects. QT prolongation and TdP have been reported in patients treated with fluoxetine and the manufacturer recommends caution when using fluoxetine with other drugs that prolong the QT interval. Methadone is associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, both fluoxetine and methadone have central serotonergic properties and serotonin syndrome is possible. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical treatment should be implemented. Lastly, fluoxetine may inhibit the metabolism of methadone via CYP3A4 or CYP2D6. In patients treated with methadone and fluoxetine, the plasma concentration of methadone increased. Interestingly in patients treated with methadone, the R-enantiomer (the active moiety) was increased by the addition of fluoxetine. Patients may experience increases in CNS depressive effects or respiratory depression. Thus, methadone-treated patients receiving fluoxetine should be carefully monitored and dosage adjustments may be warranted. (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as olanzapine, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, concomitant use of methadone with another CNS depressant, such as olanzapine, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Olanzapine; Samidorphan: (Contraindicated) Salmidorphan is contraindicated in patients who are using opiate agonists or undergoing acute opioid withdrawal. Salmidorphan increases the risk of precipitating acute opioid withdrawal in patients dependent on opioids. Before initiating salmidorphan, there should be at least a 7-day opioid-free interval from the last use of short-acting opioids, and at least a 14-day opioid-free interval from the last use of long-acting opioids. In emergency situations, if a salmidorphan-treated patient requires opiates for anesthesia or analgesia, discontinue salmidorphan. The opiate agonist should be administered by properly trained individual(s), and the patient properly monitored in a setting equipped and staffed for cardiopulmonary resuscitation. In non-emergency situations, if a salmidorphan-treated patient requires opiate agonist treatment (e.g., for analgesia) discontinue salmidorphan at least 5 days before opioid treatment. Salmidorphan, as an opioid antagonist, may cause opioid treatment to be less effective or ineffective shortly after salmidorphan discontinuation. (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as olanzapine, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, concomitant use of methadone with another CNS depressant, such as olanzapine, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Oliceridine: (Major) Concomitant use of oliceridine with methadone may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of oliceridine with methadone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Olmesartan; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Olutasidenib: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with olutasidenib is necessary. Consider increasing the dose of methadone as needed. If olutasidenib is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; olutasidenib is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Omaveloxolone: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with omaveloxolone is necessary. Consider increasing the dose of methadone as needed. If omaveloxolone is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; omaveloxolone is a weak CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Ondansetron: (Major) Concomitant use of ondansetron and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary. Do not exceed 16 mg of IV ondansetron in a single dose; the degree of QT prolongation associated with ondansetron significantly increases above this dose.
Oritavancin: (Moderate) Coadministration of oritavancin and methadone may result in increases or decreases in methadone exposure and may increase side effects or decrease efficacy of methadone. Methadone is metabolized by CYP3A4, CYP2D6, CYP2C9, and CYP2C19. Oritavancin weakly induces CYP3A4 and CYP2D6, while weakly inhibiting CYP2C9 and CYP2C19. If these drugs are administered concurrently, monitor the patient for signs of toxicity or lack of efficacy, including abstinence syndrome in a patient who had developed physical dependence.
Orphenadrine: (Major) Concomitant use of methadone with orphenadrine may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with orphenadrine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Osilodrostat: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of osilodrostat is necessary; these effects may be more pronounced with osilodrostat as it can inhibit multiple CYP enzymes. If osilodrostat is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2D6, and CYP2C19; osilodrostat is a weak CYP3A4, CYP2D6, and CYP2C19 inhibitor. Concomitant use with osilodrostat can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Osimertinib: (Major) Avoid coadministration of methadone with osimertinib if possible due to the risk of QT prolongation and torsade de pointes (TdP). If concomitant use is unavoidable, use extreme caution; monitor ECGs for QT prolongation and monitor electrolytes. An interruption of osimertinib therapy with dose reduction or discontinuation of therapy may be necessary if QT prolongation occurs. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Oxaliplatin: (Major) The need to coadminister methadone with oxaliplatin should be done with extreme caution and a careful assessment of treatment risks versus benefits. Monitor electrolytes and ECGs for QT prolongation if coadministration of methadone with oxaliplatin is necessary; correct electrolyte abnormalities prior to administration of oxaliplatin. QT prolongation and ventricular arrhythmias including fatal torsade de pointes (TdP) have been reported with oxaliplatin use in post-marketing experience. Methadone is also considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg per day, averaging approximately 400 mg per day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Additive QT prolongation is possible.
Oxazepam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Oxycodone: (Major) Concomitant use of methadone with another CNS depressant, such as oxycodone, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also, consider a using a lower dose of the CNS depressant; use an initial dose of oxycodone at one-third to one-half the usual dosage. Monitor patients for sedation and respiratory depression.
Oxymorphone: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Ozanimod: (Major) In general, do not initiate ozanimod in patients taking methadone due to the risk of bradycardia, QT prolongation, and torsade de pointes (TdP). Additionally, there is a potential for increased blood pressure and serotonin syndrome. If treatment initiation is considered, seek advice from a cardiologist and monitor for hypertension. Ozanimod may result in a transient decrease in heart rate and atrioventricular conduction delays. An active metabolite of ozanimod inhibits monoamine oxidase B (MAO-B). The concomitant use of opioids with MAO inhibitors has resulted in serotonin syndrome. Ozanimod has not been studied in patients taking concurrent QT prolonging drugs; however, QT prolonging drugs have been associated with TdP in patients with bradycardia. Methadone is a serotonergic drug that is associated with QT prolongation and TdP, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Although a small number of patients treated with ozanimod were concomitantly exposed to opioids, this exposure was not adequate to rule out the possibility of an adverse reaction from co-administration.
Pacritinib: (Major) Concomitant use of pacritinib and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Methadone exposure may also increase. Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation. If pacritinib is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4; pacritinib is a CYP3A4 inhibitor. Concomitant use with pacritinib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Palbociclib: (Moderate) Closely monitor for an increase in methadone-related adverse reactions (e.g., sedation, respiratory depression) if coadministration with palbociclib is necessary. Consider a methadone dose reduction until stable drug effects are achieved. The addition of palbociclib, a weak time-dependent inhibitor of CYP3A, and methadone, a sensitive CYP3A4 substrate, may increase methadone serum concentrations and prolong opioid adverse effects. Fatal respiratory depression may occur, especially if a CYP3A4 inhibitor is added to a stable dose of methadone. If palbociclib is discontinued, monitor for signs of opioid withdrawal.
Paliperidone: (Major) Paliperidone has been associated with QT prolongation; torsade de pointes (TdP) and ventricular fibrillation have been reported in the setting of overdose. According to the manufacturer, since paliperidone may prolong the QT interval, it should be avoided in combination with other agents also known to have this effect, such as methadone. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. If coadministration is necessary and the patient has known risk factors for cardiac disease or arrhythmias, close monitoring is essential. Also monitor patients for additive sedation during concurrent use.
Panobinostat: (Major) QT prolongation has been reported with panobinostat therapy in patients with multiple myeloma in a clinical trial; use of panobinostat with other agents that prolong the QT interval is not recommended. Obtain an electrocardiogram at baseline and periodically during treatment. Hold panobinostat if the QTcF increases to >= 480 milliseconds during therapy; permanently discontinue if QT prolongation does not resolve. Drugs with a possible risk for QT prolongation and torsade de pointes that should be used cautiously and with close monitoring with panobinostat include methadone.
Paroxetine: (Moderate) Monitor patients for respiratory depression and sedation at frequent intervals if concomitant administration of methadone and paroxetine is necessary; consider reducing the methadone dose until stable effects are achieved. Concomitant use of methadone and paroxetine may increase the plasma concentration of methadone, resulting in increased or prolonged opioid effects. If paroxetine is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2D6 substrate and paroxetine is a CYP2D6 inhibitor. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Pasireotide: (Major) The need to coadminister methadone with pasireotide should be done with extreme caution and a careful assessment of treatment risks versus benefits, as coadministration may have additive effects on the prolongation of the QT interval. At high doses, methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses averaging approximately 400 mg/day.
Pazopanib: (Major) Coadministration of pazopanib and other drugs that prolong the QT interval is not advised; pazopanib has been reported to prolong the QT interval. At high doses, methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP). If pazopanib and methadone must be continued, closely monitor the patient for QT interval prolongation. In addition, pazopanib is a weak inhibitor of CYP3A4 and CYP2D6. Coadministration of pazopanib and methadone, a CYP3A4 and CYP2D6 substrate, may cause an increase in systemic concentrations of methadone. Use caution when concurrent administration of pazopanib and methadone is necessary.
Peginterferon Alfa-2a: (Major) Addition of peginterferon alfa-2a 180 mcg SC once weekly to methadone maintenance therapy resulted in 10 to 15% higher mean methadone pharmacokinetic parameter values after 4 weeks of dual therapy as compared with baseline values. The pharmacokinetic parameter values of peginterferon alfa-2a were not altered by methadone. Patients received a median methadone dose of 95 mg (range, 30150 mg). If both drugs will be used concomitantly, the dosage of methadone may need to be lowered. Patients need to be cautioned to not drive or operate machinery until the effects of both drugs on them are known.
Peginterferon Alfa-2b: (Major) The administration of weekly peginterferon alfa-2b 1.5 mcg/kg to patients on methadone treatment may be associated with increases in methadone AUC. After 4 weeks of peginterferon alfa-2b, a mean increase of 16% in methadone AUC occurred; 2 of the 18 patients experienced an approximate doubling in methadone AUC. All patients were on stable methadone maintenance therapy of at least 40 mg daily. The methadone dose may need to be reduced in patients who also take peginterferon alfa-2b. As too much methadone can be fatal, use with peginterferon alfa-2b should be with extreme caution. If the drugs are used together, carefully monitor patients for an increased narcotic effect.
Pegvisomant: (Moderate) In clinical trials, patients taking opiate agonists often required higher serum pegvisomant concentrations to achieve appropriate IGF-I suppression compared with patients not receiving opiate agonists. The mechanism of this interaction is unknown.
Pentamidine: (Major) Pentamidine has been associated with QT prolongation. Methadone may inhibit cardiac potassium channels and may prolong the QT interval. The need to coadminister methadone or pentamidine with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Pentazocine: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as methadone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
Pentazocine; Naloxone: (Major) Avoid the concomitant use of pentazocine and opiate agonists, such as methadone. Pentazocine is a mixed opiate agonist/antagonist that may block the effects of opiate agonists and reduce analgesic effects. Pentazocine may cause withdrawal symptoms in patients receiving chronic opiate agonists. Concurrent use of pentazocine with other opiate agonists can cause additive CNS, respiratory, and hypotensive effects. The additive or antagonistic effects are dependent upon the dose of the opiate agonist used; antagonistic effects are more common at low to moderate doses of the opiate agonist.
Pentobarbital: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Perampanel: (Moderate) Concomitant use of opioid agonists with perampanel may cause excessive sedation and somnolence. Limit the use of opioid pain medications with perampanel to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Perindopril; Amlodipine: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Perphenazine: (Minor) Perphenazine should be used cautiously and with close monitoring with methadone. Perphenazine, a phenothiazine, is associated with a possible risk for QT prolongation. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP2D6. Concurrent use of methadone with inhibitors of this enzyme, such as perphenazine, may result in increased serum concentrations of methadone Phenothiazines can also potentiate the CNS-depressant action of methadone. Caution should be exercised during simultaneous use of these agents due to potential excessive CNS effects or additive hypotension.
Perphenazine; Amitriptyline: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus. (Minor) Perphenazine should be used cautiously and with close monitoring with methadone. Perphenazine, a phenothiazine, is associated with a possible risk for QT prolongation. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP2D6. Concurrent use of methadone with inhibitors of this enzyme, such as perphenazine, may result in increased serum concentrations of methadone Phenothiazines can also potentiate the CNS-depressant action of methadone. Caution should be exercised during simultaneous use of these agents due to potential excessive CNS effects or additive hypotension.
Pexidartinib: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with pexidartinib is necessary. Consider increasing the dose of methadone as needed. If pexidartinib is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4; pexidartinib is a moderate CYP3A4 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Phenelzine: (Major) Coadministration of methadone with monoamine oxidase inhibitors (MAOIs) or within 14 days after discontinuation of treatment with an MAOI is not recommended due to the risk of serotonin syndrome and/or respiratory depression.
Phenobarbital: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Phenobarbital; Hyoscyamine; Atropine; Scopolamine: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Phenytoin: (Moderate) Additive CNS depression including respiratory depression, hypotension, profound sedation, or coma may occur with the combined use of the hydantoin (e.g., phenytoin, fosphenytoin, and ethotoin) and methadone. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression. Methadone is a primary substrate for the CYP3A4 isoenzyme. Serum concentrations of methadone may decrease due to CYP3A4 induction by phenytoin, fosphenytoin, and possibly ethotoin; withdrawal symptoms may occur.
Pimavanserin: (Major) Pimavanserin may cause QT prolongation and should generally be avoided in patients receiving other medications known to prolong the QT interval, such as methadone. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Coadministration may increase the risk for QT prolongation.
Pimozide: (Contraindicated) Pimozide is associated with a well-established risk of QT prolongation and torsade de pointes (TdP). Because of the potential for TdP, use of methadone with pimozide is contraindicated.
Pirtobrutinib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of pirtobrutinib is necessary. If pirtobrutinib is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; pirtobrutinib is a weak CYP2C19 and CYP3A inhibitor. Concomitant use with pirtobrutinib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Pitolisant: (Major) Avoid coadministration of pitolisant with methadone as concurrent use may increase the risk of QT prolongation. Pitolisant prolongs the QT interval. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Ponesimod: (Major) In general, do not initiate ponesimod in patients taking methadone due to the risk of additive bradycardia, QT prolongation, and torsade de pointes (TdP). If treatment initiation is considered, seek advice from a cardiologist. Ponesimod initiation may result in a transient decrease in heart rate and atrioventricular conduction delays. Ponesimod has not been studied in patients taking concurrent QT prolonging drugs; however, QT prolonging drugs have been associated with TdP in patients with bradycardia. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Posaconazole: (Contraindicated) The concurrent use of posaconazole and methadone is contraindicated due to the risk of life threatening arrhythmias such as torsades de pointes (TdP). Posaconazole is a potent inhibitor of CYP3A4, an isoenzyme partially responsible for the metabolism of methadone, Further, both posaconazole and methadone are substrates of the drug efflux protein, P-glycoprotein, which when administered together may increase the absorption or decrease the clearance of the other drug. This complex interaction may ultimately result in altered plasma concentrations of both posaconazole and methadone and an increased risk for serious adverse events. Additionally, posaconazole has been associated with prolongation of the QT interval as well as rare cases of TdP; avoid use with other drugs that may prolong the QT interval and are metabolized through CYP3A4, such as methadone.
Potassium Phosphate; Sodium Phosphate: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Pramipexole: (Major) Concomitant use of opioid agonists with pramipexole may cause excessive sedation and somnolence. Limit the use of opioid pain medications with pramipexole to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Dopaminergic agents like pramipexole have also been associated with sudden sleep onset during activities of daily living such as driving, which has resulted in accidents in some cases. Prescribers should re-assess patients for drowsiness or sleepiness regularly throughout treatment, especially since events may occur well after the start of treatment.
Pramlintide: (Major) Pramlintide slows gastric emptying and the rate of nutrient delivery to the small intestine. Medications with the potential to slow GI motility, such as opiate agonists, should be used with caution, if at all, with pramlintide until more data are available from the manufacturer. Monitor blood glucose.
Prasugrel: (Moderate) Consider the use of a parenteral anti-platelet agent for patients with acute coronary syndrome who require concomitant opioid agonists. Coadministration of opioid agonists with prasugrel delays and reduces the absorption of prasugrel's active metabolite due to slowed gastric emptying.
Pregabalin: (Major) Concomitant use of opioid agonists with pregabalin may cause excessive sedation, somnolence, and respiratory depression. Limit the use of opioid pain medications with pregabalin to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, initiate pregabalin at the lowest recommended dose and monitor patients for symptoms of respiratory depression and sedation. Use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression and respiratory depression.
Prilocaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Prilocaine; Epinephrine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Primaquine: (Major) Due to the potential for QT interval prolongation with primaquine, caution is advised with other drugs that prolong the QT interval. Drugs with a possible risk for QT prolongation and TdP that should be used cautiously and with close monitoring with primaquine include methadone.
Primidone: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Procainamide: (Major) The need to coadminister methadone with procainamide should be done with extreme caution and a careful assessment of treatment risks versus benefits. Procainamide administration is associated with QT prolongation and torsades de pointes (TdP). Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Procarbazine: (Moderate) Opiate agonists may cause additive sedation or other CNS effects when given in combination with procarbazine.
Prochlorperazine: (Minor) Prochlorperazine should be used cautiously and with close monitoring with methadone. Prochlorperazine, a phenothiazine, is associated with a possible risk for QT prolongation. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, phenothiazines can potentiate the CNS-depressant action of methadone. Caution should be exercised during simultaneous use of these agents due to potential excessive CNS effects or additive hypotension.
Promethazine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Drugs with a potential risk for QT prolongation that should be used cautiously with methadone include promethazine. Additionally, use of methadone with another CNS depressant can lead to additive sedation, respiratory depression, hypotension, or coma. Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; for example, in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Promethazine; Dextromethorphan: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Drugs with a potential risk for QT prolongation that should be used cautiously with methadone include promethazine. Additionally, use of methadone with another CNS depressant can lead to additive sedation, respiratory depression, hypotension, or coma. Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; for example, in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Promethazine; Phenylephrine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Drugs with a potential risk for QT prolongation that should be used cautiously with methadone include promethazine. Additionally, use of methadone with another CNS depressant can lead to additive sedation, respiratory depression, hypotension, or coma. Because promethazine causes pronounced sedation, an enhanced CNS depressant effect or additive drowsiness may occur when it is combined with other CNS depressants. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; for example, in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Propafenone: (Major) Due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering propafenone with methadone. The need to coadminister these drugs should be done with a careful assessment of treatment risks versus benefits. Propafenone is a Class IC antiarrhythmic which increases the QT interval largely due to prolongation of the QRS interval. Methadone is also considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Propafenone inhibits CYP2D6 and P-gp. Concurrent use may result in increased serum concentrations of methadone.
Propofol: (Moderate) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma; examples include general anesthetics. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Protriptyline: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Pseudoephedrine; Triprolidine: (Moderate) Concomitant use of opioid agonists with triprolidine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with triprolidine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Pyrilamine: (Moderate) Concomitant use of opioid agonists with pyrilamine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with pyrilamine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Quazepam: (Major) Concurrent use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective dose and minimum duration possible. If methadone is initiated for pain in an opioid-naive patient taking a benzodiazepine, use an initial methadone dose of 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial benzodiazepine dose and titrate to response. In patients treated with methadone for opioid use disorder, cessation of benzodiazepines or other CNS depressants is preferred in most cases. Consider alternatives to benzodiazepines for conditions such as anxiety or insomnia during methadone maintenance treatment. Educate patients about the risks and symptoms of respiratory depression and sedation.
Quetiapine: (Major) Concurrent use of quetiapine and methadone should be avoided due to an increased risk for QT prolongation and torsade de pointes (TdP). The need to coadminister these drugs should be done with extreme caution and a careful assessment of treatment risks versus benefits. Limited data, including some case reports, suggest that quetiapine may be associated with a significant prolongation of the QTc interval in rare instances. Methadone is also considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses averaging approximately 400 mg/day in adult patients. In addition, concomitant use of methadone with another CNS depressant, such as quetiapine, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Quinidine: (Contraindicated) Quinidine administration is associated with QT prolongation and torsades de pointes (TdP). Quinidine inhibits CYP2D6 and has QT-prolonging actions; quinidine is contraindicated with other drugs that prolong the QT interval and are metabolized by CYP2D6 as the effects on the QT interval may be increased during concurrent use of these agents. Drugs that prolong the QT and are substrates for CYP2D6 that are contraindicated with quinidine include methadone.
Quinine: (Major) Concurrent use of quinine and methadone should be avoided due to an increased risk for QT prolongation and torsade de pointes (TdP). Quinine has been associated with prolongation of the QT interval and rare cases of TdP. Methadone is also considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, concentrations of methadone may be increased with concomitant use of quinine. Methadone is a CYP3A4 and CYP2D6 substrate and quinine is a CYP3A4/CYP2D6 inhibitor.
Quizartinib: (Major) Concomitant use of quizartinib and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Ramelteon: (Moderate) Concomitant use of opioid agonists with ramelteon may cause excessive sedation and somnolence. Limit the use of opioid pain medications with ramelteon to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Ranolazine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. At high doses, methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses averaging approximately 400 mg/day. In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with inhibitors of these enzymes may result in increased serum concentrations of methadone. Drugs with a possible risk for QT prolongation and TdP that inhibit CYP3A4, CYP2D6, and P-gp that should be used cautiously with methadone include ranolazine.
Rasagiline: (Contraindicated) Methadone use in patients taking rasagiline or within 14 days of stopping such treatment is contraindicated due to the risk of serotonin syndrome.
Relugolix: (Major) The need to coadminister methadone with drugs known to prolong the QT interval such as relugolix should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy (i.e., relugolix) may also prolong the QT/QTc interval.
Relugolix; Estradiol; Norethindrone acetate: (Major) The need to coadminister methadone with drugs known to prolong the QT interval such as relugolix should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy (i.e., relugolix) may also prolong the QT/QTc interval.
Remifentanil: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Remimazolam: (Major) Concomitant use of opioid agonists with remimazolam may cause respiratory depression, hypotension, profound sedation, and death. Titrate the dose of remimazolam to the desired clinical response and continuously monitor sedated patients for hypotension, airway obstruction, hypoventilation, apnea, and oxygen desaturation.
Ribociclib: (Major) Avoid coadministration of ribociclib with methadone due to an increased risk for QT prolongation and torsade de pointes (TdP). Systemic exposure of methadone may also be increased resulting in an increase in methadone-related adverse reactions including respiratory depression and sedation. Ribociclib is a strong CYP3A4 inhibitor that has been shown to prolong the QT interval in a concentration-dependent manner. Methadone is a CYP3A4 substrate that has also been associated with an increased risk of QT prolongation and TdP, especially at higher doses (greater than 200 mg per day but averaging approximately 400 mg per day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Concomitant use may increase the risk for QT prolongation.
Ribociclib; Letrozole: (Major) Avoid coadministration of ribociclib with methadone due to an increased risk for QT prolongation and torsade de pointes (TdP). Systemic exposure of methadone may also be increased resulting in an increase in methadone-related adverse reactions including respiratory depression and sedation. Ribociclib is a strong CYP3A4 inhibitor that has been shown to prolong the QT interval in a concentration-dependent manner. Methadone is a CYP3A4 substrate that has also been associated with an increased risk of QT prolongation and TdP, especially at higher doses (greater than 200 mg per day but averaging approximately 400 mg per day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Concomitant use may increase the risk for QT prolongation.
Rifampin: (Major) Concurrent administration of rifampin and methadone is associated with a 33 to 68% decrease in methadone levels due to induction of methadone metabolism by rifampin. When effective alternatives exist, rifampin should not be administered to patients receiving chronic methadone therapy. However, if rifampin treatment is necessary, the methadone dosage will need to be increased to maintain adequate suppression of opiate withdrawal symptoms.
Rifapentine: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with rifapentine is necessary; these effects may be more pronounced with rifapentine as it can induce multiple CYP enzymes. Consider increasing the dose of methadone as needed. If rifapentine is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4 and CYP2C9; rifapentine is a strong CYP3A4 inducer and moderate CYP2C9 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Rilpivirine: (Major) Close clinical monitoring is advised with coadministration. Use of these drugs together may cause the plasma concentration of methadone to decrease, thereby resulting in decreased methadone efficacy. No dose adjustments are required when initiating concurrent treatment; however, the maintenance dose of methadone may need to be adjusted in some patients. In addition, due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering rilpivirine with methadone. A careful assessment of treatment risks versus benefits should be conducted prior to coadministration. When initiating concurrent treatment no dose adjustments are required; however, the dose of methadone may need to be adjusted during maintenance therapy. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Supratherapeutic doses of rilpivirine (75 to 300 mg/day) have also been associated with prolongation of the QT interval.
Risperidone: (Major) Methadone has a known risk of QT prolongation and torsade de pointes (TdP) and a careful assessment of risks versus benefits should be performed before coadministration with drugs having a possible risk of QT prolongation and TdP such as risperidone. Methadone is particularly associated with an increased risk for QT prolongation and TdP at higher doses (e.g., 400 mg/day in adults). Concomitant use of CNS depressants, such as risperidone and methadone, can lead to additive CNS depression, hypotension, or coma. Prior to the use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, the patient's overall response to treatment, and the patient's use of alcohol or illicit drugs. In opioid-naive adults, initiate methadone at a dose of 2.5 mg every 12 hours in patients receiving other CNS depressants. Also consider using a lower dose of the CNS depressant.
Ritlecitinib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of ritlecitinib is necessary. If ritlecitinib is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; ritlecitinib is a moderate CYP3A inhibitor. Concomitant use with ritlecitinib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Ritonavir: (Moderate) Coadministration of ritonavir with methadone has resulted in decreased methadone plasma concentrations. However, because methadone is metabolized by multiple CYP450 enzymes, including CYP3A4, CYP2C19, CYP2C9, and CYP2D6, and ritonavir is known to inhibit CYP3A4 and CYP2D6 and induce CYP2C19 and CYP2C9, the potential for increased methadone exposure should also be considered with concomitant administration. Therefore, concurrent use may increase or prolong opioid effects, resulting in fatal overdose or may decrease methadone efficacy or produce onset of withdrawal symptoms in patients physically dependent on methadone. Monitor for respiratory depression, sedation, and signs of opioid withdrawal. Consider adjusting the methadone dose until stable drug effects are achieved. If ritonavir is discontinued, and its CYP450 effects decline, methadone plasma concentrations may increase or decrease. Closely monitor for increased opioid adverse effects and for evidence of withdrawal and adjust the methadone dose as necessary when ritonavir is discontinued.
Rizatriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Rolapitant: (Major) Use caution if methadone and rolapitant are used concurrently, and monitor for methadone-related adverse effects. Methadone is a substrate of CYP2D6 and P-glycoprotein (P-gp), where an increase in exposure may significantly increase adverse effects; rolapitant is an inhibitor of CYP2D6 and P-gp. The inhibitory effect of rolapitant is expected to persist beyond 28 days for an unknown duration. Exposure to another CYP2D6 substrate, following a single dose of rolapitant increased about 3-fold on Days 8 and Day 22. The inhibition of CYP2D6 persisted on Day 28 with a 2.3-fold increase in the CYP2D6 substrate concentrations, the last time point measured. When oral rolapitant was administered with another P-gp substrate, the day 1 Cmax and AUC were increased by 70% and 30%, respectively; the Cmax and AUC on day 8 were not studied. When the P-gp substrate was administered with a single dose of intravenous rolapitant, no effect on AUC and a 21% increase in the Cmax of P-gp substrate was observed.
Romidepsin: (Major) Romidepsin has been reported to prolong the QT interval. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. If romidepsin and methadone must be coadministered, appropriate cardiovascular monitoring precautions should be considered, such as the monitoring of electrolytes and ECGs at baseline and periodically during treatment.
Ropinirole: (Major) Concomitant use of opioid agonists with ropinirole may cause excessive sedation and somnolence. Limit the use of opioid pain medication with ropinirole to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Dopaminergic agents have also been associated with sudden sleep onset during activities of daily living such as driving, which has resulted in accidents in some cases. Reassess patients for drowsiness or sleepiness regularly throughout treatment, especially since events may occur well after the start of treatment.
Ropivacaine: (Moderate) The use of these drugs together must be approached with caution. Although commonly used together for additive analgesic effects, the patient must be monitored for respiratory depression, hypotension, and excessive sedation due to additive effects on the CNS and blood pressure. In rare instances, serious morbidity and mortality has occurred. Limit the use of opiate pain medications with local anesthetics to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. The use of the local anesthetic will allow for the use a lower initial dose of the opiate and then the doses can be titrated to proper clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Rotigotine: (Major) Concomitant use of opioid agonists with rotigotine may cause excessive sedation and somnolence. Limit the use of opioid pain medications with rotigotine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Dopaminergic agents like rotigotine have also been associated with sudden sleep onset during activities of daily living such as driving, which has resulted in accidents in some cases. Prescribers should re-assess patients for drowsiness or sleepiness regularly throughout treatment, especially since events may occur well after the start of treatment.
Rucaparib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of rucaparib is necessary. If rucaparib is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP3A4, CYP2C9, and CYP2C19 substrate; rucaparib is a weak inhibitor of CYP3A4, CYP2C9, and CYP2C19. Coadministration can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If rucaparib is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Safinamide: (Contraindicated) Concomitant use of safinamide with opioids is contraindicated due to the risk of serotonin syndrome. Allow at least 14 days between discontinuation of safinamide and initiation of treatment with opioids.
Saquinavir: (Major) Concurrent use of methadone and saquinavir boosted with ritonavir should be avoided if possible due to the risk of life threatening cardiac arrhythmias such as torsade de pointes (TdP). If no alternative therapy is acceptable, perform a baseline ECG prior to initiation of concomitant therapy and follow recommended ECG monitoring. Saquinavir boosted with ritonavir causes dose-dependent QT and PR prolongation. Methadone may also prolong the QT interval. Additionally, administering methadone (60 to 120 mg daily) in combination with saquinavir/ritonavir (1000/100 mg twice daily) has resulted in a decrease in both methadone and saquinavir serum concentrations. Monitor patients carefully and adjust the methadone dose if necessary.
Secobarbital: (Major) Concomitant use of methadone with a barbiturate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a barbiturate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation. Additionally, concurrent use of methadone with a barbiturate may decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to opioid agonists. Monitor for signs of opioid withdrawal. Discontinuation of a barbiturate may increase the risk of increased opioid-related adverse reactions, such as fatal respiratory depression. Barbiturates are inducers of CYP3A4, CYP2C9, and CYP2C19, isoenzymes partially responsible for the metabolism of methadone.
Selegiline: (Contraindicated) Coadministration of methadone and selegiline is contraindicated due to a risk for serotonin syndrome and opioid toxicity, including respiratory depression. At least 14 days should elapse between discontinuation of selegiline and initiation of treatment with methadone. After stopping treatment with methadone, a time period equal to 4 to 5 half-lives of methadone or any active metabolite should elapse before starting therapy with selegiline. If urgent use of an opioid is necessary, use test doses and frequent titration of small doses of an alternate opioid to treat pain while closely monitoring blood pressure and signs and symptoms of CNS and respiratory depression.
Selpercatinib: (Major) Monitor ECGs more frequently for QT prolongation if coadministration of selpercatinib with methadone is necessary due to the risk of additive QT prolongation. Systemic exposure of methadone may also be increased, resulting in increased or prolonged opioid effects, particularly when selpercatinib is added after a stable methadone dose is achieved. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of selpercatinib is necessary. If selpercatinib is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a CYP3A4 substrate that is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Selpercatinib is a weak CYP3A4 inhibitor that has been shown to prolong the QT interval in a concentration-dependent manner.
Serotonin-Receptor Agonists: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Sertraline: (Major) Coadministration should be avoided if possible due to the potential risk of serotonin syndrome, QT prolongation or torsade de pointes (TdP), or opioid-related side effects. There have been postmarketing reports of QT prolongation and TdP during treatment with sertraline and the manufacturer of sertraline recommends avoiding concurrent use with drugs known to prolong the QTc interval. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, both sertraline and methadone have central serotonergic properties and serotonin syndrome is possible. Serotonin syndrome is characterized by the rapid development of hyperthermia, hypertension, myoclonus, rigidity, autonomic instability, mental status changes (e.g., delirium or coma), and in rare cases, death. If serotonin syndrome occurs, all serotonergic agents should be discontinued and appropriate medical treatment should be implemented. Lastly, sertraline is a CYP2D6 inhibitor and methadone is partially metabolized by CYP2D6, which may increase the risk of CNS depressive effects, respiratory depression, QT prolongation, or other adverse effects.
Sevoflurane: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Halogenated anesthetics can prolong the QT interval. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Siponimod: (Major) In general, do not initiate treatment with siponimod in patients receiving methadone due to the potential for QT prolongation. Consult a cardiologist regarding appropriate monitoring if siponimod use is required. Siponimod therapy prolonged the QT interval at recommended doses in a clinical study. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes, especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Sodium Benzoate; Sodium Phenylacetate: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Sodium Oxybate: (Major) Concomitant use of opioid agonists with sodium oxybate may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medication with sodium oxybate to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Sodium Phenylbutyrate; Taurursodiol: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal and/or increased toxicity if coadministration with taurursodiol is necessary. Consider adjusting the dose of methadone as needed. Concomitant use may alter methadone exposure. If taurursodiol is discontinued, frequently monitor for signs of respiratory depression and sedation or withdrawal syndrome. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; taurursodiol is a weak CYP3A and CYP2B6 inducer and weak CYP2B6 inhibitor. The net effect on methadone exposure is unknown.
Sodium Phosphate Monobasic Monohydrate; Sodium Phosphate Dibasic Anhydrous: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Sodium Stibogluconate: (Major) Concomitant use of sodium stibogluconate and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Solifenacin: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Solifenacin has been associated with dose-dependent prolongation of the QT interval. TdP has been reported with postmarketing use, although causality was not determined. Additionally, monitor patients for signs of urinary retention or reduced gastric motility when methadone is used concomitantly with an anticholinergic drug, such as solifenacin. The concomitant use of methadone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
Sorafenib: (Major) Avoid coadministration of sorafenib with methadone due to the risk of additive QT prolongation. If concomitant use is unavoidable, monitor electrocardiograms and correct electrolyte abnormalities. An interruption or discontinuation of sorafenib therapy may be necessary if QT prolongation occurs. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg per day but averaging approximately 400 mg per day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Sorafenib is also associated with QTc prolongation.
Sotalol: (Major) Concomitant use of sotalol and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Sotorasib: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with sotorasib is necessary. Consider increasing the dose of methadone as needed. If sotorasib is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; sotorasib is a moderate CYP3A inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Sparsentan: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with sparsentan is necessary. Consider increasing the dose of methadone as needed. If sparsentan is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; sparsentan is a weak CYP2B6, CYP2C19, and CYP2C9 inducer.
Spironolactone: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of spironolactone is necessary. If spironolactone is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; spironolactone is a weak CYP3A inhibitor. Concomitant use with spironolactone can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. Additionally, monitor for decreased diuretic efficacy and additive orthostatic hypotension when spironolactone is administered with methadone. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
Spironolactone; Hydrochlorothiazide, HCTZ: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of spironolactone is necessary. If spironolactone is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; spironolactone is a weak CYP3A inhibitor. Concomitant use with spironolactone can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. Additionally, monitor for decreased diuretic efficacy and additive orthostatic hypotension when spironolactone is administered with methadone. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
St. John's Wort, Hypericum perforatum: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with St. John's Wort is necessary; these effects may be more pronounced with St. John's Wort as it can induce multiple CYP enzymes. Consider increasing the dose of methadone as needed. If St. John's Wort is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, and CYP2C9. St. John's Wort is a CYP3A4, CYP2B6, CYP2C19, and CYP2C9 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Stavudine, d4T: (Minor) Methadone decreases the bioavailability stavudine, d4T by slowing its absorption and increasing its first-pass metabolism. As a result, stavudine's AUC and Cmax are decreased by 18% and 39%, respectively; however, these effects are probably not clinically significant.
Stiripentol: (Moderate) Concomitant use of opioid agonists with stiripentol may cause excessive sedation and somnolence. Limit the use of opioid pain medications with stiripentol to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression. Coadministration may alter plasma concentrations of methadone resulting in an increased risk of adverse reactions and/or decreased efficacy. Methadone is a CYP3A4 substrate. In vitro data predicts inhibition or induction of CYP3A4 by stiripentol potentially resulting in clinically significant interactions.
Streptogramins: (Moderate) Concomitant use of methadone with dalfopristin; quinupristin may increase methadone plasma concentrations and prolong opioid adverse reactions, including hypotension, respiratory depression, profound sedation, coma, and death. Monitor patients closely at frequent intervals and consider a dosage reduction of methadone until stable drug effects are achieved. Discontinuation of dalfopristin; quinupristin could decrease methadone plasma concentrations, decrease opioid efficacy, and potentially lead to a withdrawal syndrome in those with physical dependence to methadone. If dalfopristin; quinupristin is discontinued, monitor the patient carefully and consider increasing the opioid dosage if appropriate. Methadone is a substrate for CYP3A4. Dalfopristin; quinupristin is a weak inhibitor of CYP3A4.
Sufentanil: (Major) Concomitant use of methadone with another CNS depressant can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressant, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Sumatriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Sumatriptan; Naproxen: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Sunitinib: (Major) Coadministration of methadone with drugs known to prolong the QT interval, such as sunitinib, should be done with extreme caution and a careful assessment of treatment risks versus benefits; monitor patients for QT prolongation. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day, but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Sunitinib can cause dose-dependent QT prolongation, which may increase the risk for ventricular arrhythmias, including TdP.
Suvorexant: (Moderate) Concomitant use of opioid agonists with suvorexant may cause excessive sedation and somnolence. Limit the use of opioid pain medications with suvorexant to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Tacrolimus: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as tacrolimus, should be done with extreme caution and a careful assessment of treatment risks versus benefits. When coadministering tacrolimus with other substrates of CYP3A, especially those that also have the potential to prolong the QT interval, such as methadone, monitoring of tacrolimus whole blood concentrations, and monitoring for QT prolongation is recommended. Consider obtaining electrocardiograms (ECGs) and monitoring electrolytes (magnesium, potassium, calcium) periodically during treatment in at-risk patients. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tacrolimus may also prolong the QT interval and has been reported to cause TdP.
Tamoxifen: (Major) Concomitant use of tamoxifen and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Tapentadol: (Major) Concomitant use of tapentadol with methadone may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of tapentadol with methadone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Also monitor patients for the emergence of serotonin syndrome. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome.
Tasimelteon: (Moderate) Concomitant use of opioid agonists with tasimelteon may cause excessive sedation and somnolence. Limit the use of opioid pain medications with tasimelteon to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Tazemetostat: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with tazemetostat is necessary. Consider increasing the dose of methadone as needed. If tazemetostat is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4; tazemetostat is a weak CYP3A4 inducer. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Tedizolid: (Major) Avoid concomitant use of methadone in patients receiving tedizolid or within 14 days of stopping treatment with tedizolid due to the risk of serotonin syndrome or opioid toxicity, including respiratory depression.
Telavancin: (Major) Due to the potential for QT prolongation and torsade de pointes (TdP), caution is advised when administering telavancin with methadone. The need to coadminister these drugs should be done with careful assessment of treatment risks versus benefits. Telavancin has been associated with QT prolongation. Methadone is considered to be associated with an increased risk for QT prolongation and TdP, especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Telmisartan; Amlodipine: (Moderate) Frequently monitor for respiratory depression and sedation if concurrent use of amlodipine is necessary; consider reducing the dose of methadone if clinically appropriate. If amlodipine is discontinued, monitor for evidence of opioid withdrawal; consider increasing the methadone dose if needed. Methadone is a CYP3A4 substrate; coadministration with a weak CYP3A4 inhibitor like amlodipine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If amlodipine is discontinued, methadone plasma concentrations may decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Telotristat Ethyl: (Moderate) Monitor for reduced efficacy of methadone and signs of opioid withdrawal if coadministration with telotristat is necessary; these effects may be more pronounced with telotristat as it can induce multiple CYP enzymes. Consider increasing the dose of methadone as needed. If telotristat is discontinued, consider a dose reduction of methadone and frequently monitor for signs of respiratory depression and sedation. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6. Telotristat is a weak CYP3A4 inducer and based on in vitro studies, potential induction of CYP2B6 in vivo by telotristat cannot be ruled out. Concomitant use can decrease methadone exposure resulting in decreased efficacy or onset of a withdrawal syndrome in patients who have developed physical dependence.
Temazepam: (Major) Concomitant use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If methadone is initiated in a patient taking a benzodiazepine, reduced dosages are recommended; in opioid-naive adults, use an initial dose of methadone 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Terbinafine: (Moderate) Coadministration of methadone and terbinafine may result in increased methadone concentrations. Systemic terbinafine inhibits hepatic isoenzyme CYP2D6, and thus may inhibit the clearance of drugs metabolized by this isoenzyme.
Tetrabenazine: (Major) Tetrabenazine causes a small increase in the corrected QT interval (QTc). The manufacturer recommends avoiding concurrent use of tetrabenazine with other drugs known to prolong QTc such as methadone. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. In addition, concurrent use of methadone and tetrabenazine should generally be avoided since the risk of adverse effects such as drowsiness, sedation, dizziness, or orthostatic hypotension may be increased.
Tezacaftor; Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as methadone. Ivacaftor is an inhibitor of CYP3A, P-glycoprotein (Pgp), and a weak inhibitor of CYP2C9; methadone is metabolized by CYP3A4, CYP2C9, and is a substrate of Pgp. Co-administration of ivacaftor with CYP3A, CYP2C9, and Pgp substrates,such as methadone may increase methadone exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Thalidomide: (Major) Avoid coadministration of opioid agonists with thalidomide due to the risk of additive CNS depression.
Thiazide diuretics: (Moderate) Diuretics can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with diuretics is needed. In addition, opiate agonists may potentiate orthostatic hypotension when used concurrently with diuretics.
Thioridazine: (Contraindicated) Because of the potential for torsades de pointes (TdP), concurrent use of methadone and thioridazine is contraindicated. Thioridazine is associated with a well-established risk of QT prolongation and torsades de pointes (TdP) and is considered contraindicated for use along with agents that, when combined with a phenothiazine, may prolong the QT interval and increase the risk of TdP, and/or cause orthostatic hypotension. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Thiotepa: (Moderate) The concomitant use of thiotepa and methadone may increase the exposure of methadone; however, the clinical relevance of this interaction is unknown. Thiotepa is a CYP2B6 inhibitor in vitro; methadone is a CYP2B6 substrate.
Thiothixene: (Moderate) Concomitant use of opioid agonists like methadone with thiothixene may cause excessive sedation and somnolence. Limit the use of opioid pain medication with thiothixene to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Ticagrelor: (Moderate) Coadministration of opioid agonists, such as methadone, may delay and reduce the absorption of ticagrelor resulting in reduced exposure and diminished inhibition of platelet aggregation. Consider the use of a parenteral antiplatelet agent in acute coronary syndrome patients requiring an opioid agonist. Mean ticagrelor exposure decreased up to 36% in ACS patients undergoing PCI when intravenous morphine was administered with a loading dose of ticagrelor; mean platelet aggregation was higher up to 3 hours post loading dose. Similar effects on ticagrelor exposure and platelet inhibition were observed when fentanyl was administered with a ticagrelor loading dose in ACS patients undergoing PCI. Although exposure to ticagrelor was decreased up to 25% in healthy adults administered intravenous morphine with a loading dose of ticagrelor, platelet inhibition was not delayed or decreased in this population.
Tipranavir: (Moderate) Protease inhibitors may interact with methadone to varying degrees. Most of the protease inhibitors reduce the metabolism of methadone, and there is a potential for excessive methadone-related side effects.
Tizanidine: (Major) Concomitant use of methadone with a skeletal muscle relaxant may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opioid pain medications with a skeletal muscle relaxant to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. Educate patients about the risks and symptoms of respiratory depression and sedation.
Tolterodine: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tolterodine has been associated with dose-dependent prolongation of the QT interval, especially in poor CYP2D6 metabolizers. Additionally, monitor patients for signs of urinary retention or reduced gastric motility when methadone is used concomitantly with an anticholinergic drug, such as tolterodine. The concomitant use of methadone and anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect.
Toremifene: (Major) Avoid coadministration of methadone with toremifene if possible due to the risk of additive QT prolongation. If concomitant use is unavoidable, closely monitor ECGs for QT prolongation and monitor electrolytes; correct hypokalemia or hypomagnesemia prior to administration of toremifene. Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation. If toremifene is discontinued, consider increasing the methadone dose until stable drug effects are achieved and monitor for evidence of opioid withdrawal. Methadone is a CYP2C9 substrate that is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Toremifene is a weak CYP2C9 inhibitor that has also been shown to prolong the QTc interval in a dose- and concentration-related manner. Coadministration with weak CYP2C9 inhibitors like toremifene can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone. If toremifene is discontinued, methadone plasma concentrations will decrease resulting in reduced efficacy of the opioid and potential withdrawal syndrome in a patient who has developed physical dependence to methadone.
Torsemide: (Moderate) Diuretics can cause electrolyte disturbances such as hypomagnesemia and hypokalemia, which may prolong the QT interval. As methadone may also prolong the QT interval, cautious coadministration with diuretics is needed.
Tramadol: (Major) Concomitant use of tramadol increases the seizure risk in patients taking opiate agonists. Also, tramadol can cause additive CNS depression and respiratory depression when used with opiate agonists; avoid concurrent use whenever possible. If used together, extreme caution is needed, and a reduced tramadol dose is recommended.
Tramadol; Acetaminophen: (Major) Concomitant use of tramadol increases the seizure risk in patients taking opiate agonists. Also, tramadol can cause additive CNS depression and respiratory depression when used with opiate agonists; avoid concurrent use whenever possible. If used together, extreme caution is needed, and a reduced tramadol dose is recommended.
Trandolapril; Verapamil: (Moderate) Verapamil may increase methadone serum concentrations via inhibition of CYP3A4 metabolism of methadone. Inhibition of methadone metabolism can lead to toxicity including CNS adverse effects and potential for QT prolongation and torsades de pointes when high doses of methadone are used.
Tranylcypromine: (Major) Coadministration of methadone with monoamine oxidase inhibitors (MAOIs) or within 14 days after discontinuation of treatment with an MAOI is not recommended due to the risk of serotonin syndrome and/or respiratory depression.
Trazodone: (Major) Avoid coadministration of trazodone and methadone due to an additive risk of QT prolongation. Concomitant use of opioid agonists with trazodone may also cause excessive sedation, somnolence, and increase the risk for serotonin syndrome. Limit the use of opioid pain medications with trazodone to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of serotonin syndrome and excessive CNS depression. Trazodone can prolong the QT/QTc interval at therapeutic doses, and there are postmarketing reports of torsade de pointes (TdP). Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (i.e., more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Triamterene: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when triamterene is administered with methadone. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
Triamterene; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for decreased diuretic efficacy and additive orthostatic hypotension when triamterene is administered with methadone. Adjustments to diuretic therapy may be needed in some patients. The efficacy of diuretics may be reduced due to opioid-induced release of antidiuretic hormone.
Triazolam: (Major) Concomitant use of opiate agonists with benzodiazepines may cause respiratory depression, hypotension, profound sedation, and death. Limit the use of opiate pain medications with benzodiazepines to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. If methadone is initiated in a patient taking a benzodiazepine, reduced dosages are recommended; in opioid-naive adults, use an initial dose of methadone 2.5 mg PO every 12 hours. If a benzodiazepine is prescribed for an indication other than epilepsy in a patient taking an opiate agonist, use a lower initial dose of the benzodiazepine and titrate to clinical response. Educate patients about the risks and symptoms of respiratory depression and sedation.
Triclabendazole: (Major) Concomitant use of triclabendazole and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Tricyclic antidepressants: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Trifluoperazine: (Minor) The need to coadminister methadone with drugs known to prolong the QT interval, such as trifluoperazine, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, concomitant use of methadone with another CNS depressant, such as trifluoperazine, can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use of methadone in patients taking a CNS depressan t, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; also consider a using a lower dose of the CNS depressant. Monitor patients for sedation and respiratory depression.
Trimethobenzamide: (Moderate) The concurrent use of trimethobenzamide with other medications that cause CNS depression, like opiate agonists, may potentiate the effects of either trimethobenzamide or the opiate agonist.
Trimipramine: (Major) Concomitant use of methadone with tricyclic antidepressants may cause excessive sedation and somnolence. Limit the use of methadone with tricyclic antidepressants to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, reduce initial dosage and titrate to clinical response; use the lowest effective doses and minimum treatment durations. The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks vs. benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Tricyclic antidepressants (TCAs) share pharmacologic properties similar to the Class IA antiarrhythmic agents and may prolong the QT interval, particularly in overdose or with higher-dose therapy (elevated serum concentrations). Monitor patients closely for cardiac conduction changes. Also monitor patients for the emergence of serotonin syndrome and for signs of urinary retention or reduced gastric motility. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs. The concomitant use of opioids with other drugs that affect the serotonergic neurotransmitter system has resulted in serotonin syndrome. The concomitant use of opioids with anticholinergic drugs may increase risk of urinary retention or severe constipation, which may lead to paralytic ileus.
Triprolidine: (Moderate) Concomitant use of opioid agonists with triprolidine may cause excessive sedation and somnolence. Limit the use of opioid pain medication with triprolidine to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Triptorelin: (Major) Coadministration of methadone with triptorelin should be undertaken with extreme caution and a careful assessment of the benefits of therapy versus the risks of QT prolongation. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (greater than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Androgen deprivation therapy may prolong the QT/QTc interval.
Trofinetide: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of trofinetide is necessary. If trofinetide is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; trofinetide is a weak CYP3A inhibitor. Concomitant use with trofinetide can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Trospium: (Moderate) Monitor patients for signs of urinary retention or reduced gastric motility when trospium, an anticholinergic drug for overactive bladder, is used with opiate agonists. The concomitant use of these drugs together may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Opiates increase the tone and decrease the propulsive contractions of the smooth muscle of the gastrointestinal tract. Prolongation of the gastrointestinal transit time may be the mechanism of the constipating effect. Both agents may also cause drowsiness or blurred vision, and patients should use care in driving or performing other hazardous tasks until the effects of the drugs are known.
Tucatinib: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of tucatinib is necessary. If tucatinib is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4; tucatinib is a strong CYP3A inhibitor. Concomitant use with tucatinib can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Valerian, Valeriana officinalis: (Moderate) Concomitant use of opioid agonists with valerian may cause excessive sedation and somnolence. Limit the use of opioid pain medication with valerian to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect.
Valproic Acid, Divalproex Sodium: (Moderate) Concomitant use of opioid agonists with valproic acid may cause excessive sedation and somnolence. Limit the use of opioid pain medications with valproic acid to only patients for whom alternative treatment options are inadequate. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Educate patients about the risks and symptoms of excessive CNS depression.
Vandetanib: (Major) Avoid coadministration of vandetanib with methadone due to an increased risk of QT prolongation and torsade de pointes (TdP). If concomitant use is unavoidable, monitor ECGs for QT prolongation and monitor electrolytes; correct hypocalcemia, hypomagnesemia, and/or hypomagnesemia prior to vandetanib administration. An interruption of vandetanib therapy or dose reduction may be necessary for QT prolongation. Vandetanib can prolong the QT interval in a concentration-dependent manner; TdP and sudden death have been reported in patients receiving vandetanib. Methadone is also associated with an increased risk for QT prolongation and TdP, especially at higher doses (greater than 200 mg/day, averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction.
Vardenafil: (Major) Concomitant use of vardenafil and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Vemurafenib: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as vemurafenib, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Also, methadone is a substrate of CYP2C9, 2D6, 3A4, and P-glycoprotein (P-gp), while vemurafenib is a CYP2C9 inhibitor, a weak CYP2D6 inhibitor, a CYP3A4 substrate/inducer, and a P-gp substrate/inhibitor. Therefore, altered concentrations of methadone may occur with concomitant use. If coadministration is necessary, ECG monitoring is recommended; closely monitor the patient for QT interval prolongation.
Venlafaxine: (Major) Concomitant use of venlafaxine and methadone increases the risk of QT/QTc prolongation and torsade de pointes (TdP). Avoid concomitant use if possible, especially in patients with additional risk factors for TdP. Consider taking steps to minimize the risk for QT/QTc interval prolongation and TdP, such as electrolyte monitoring and repletion and ECG monitoring, if concomitant use is necessary.
Verapamil: (Moderate) Verapamil may increase methadone serum concentrations via inhibition of CYP3A4 metabolism of methadone. Inhibition of methadone metabolism can lead to toxicity including CNS adverse effects and potential for QT prolongation and torsades de pointes when high doses of methadone are used.
Vigabatrin: (Moderate) Vigabatrin may cause somnolence and fatigue. Drugs that can cause CNS depression, if used concomitantly with vigabatrin, may increase both the frequency and the intensity of adverse effects such as drowsiness, sedation, and dizziness. Caution should be used when vigabatrin is given with opiate agonists.
Vilazodone: (Moderate) Because of the potential risk and severity of excessive sedation, somnolence, and serotonin syndrome, caution should be observed when administering methadone with vilazodone. If concurrent use is necessary, use the lowest effective doses and minimum treatment durations needed to achieve the desired clinical effect. Inform patients taking this combination of the possible increased risks and monitor for the emergence of excessive CNS depression and serotonin syndrome, particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Viloxazine: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of viloxazine is necessary. If viloxazine is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A4, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; viloxazine is a weak CYP3A and weak CYP2D6 inhibitor. Concomitant use with viloxazine can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Vincristine Liposomal: (Minor) As methadone is a weak base, the renal elimination of methadone is increased by urine acidification. Thus acidifying agents may lower the serum methadone concentration. The limited amounts of circulating methadone that undergo glomerular filtration are partially reabsorbed by the kidney tubules, and this reabsorption is pH-dependent. Several studies have demonstrated that methadone is cleared faster from the body with an acidic urinary pH as compared with a more basic pH.
Voclosporin: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as voclosporin, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is associated with an increased risk for QT prolongation and torsade de pointes (TdP), especially at higher doses (more than 200 mg/day but averaging approximately 400 mg/day in adult patients). Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Voclosporin has been associated with QT prolongation at supratherapeutic doses.
Vonoprazan; Amoxicillin: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of vonoprazan is necessary. If vonoprazan is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; vonoprazan is a weak CYP3A and CYP2C19 inhibitor. Concomitant use with vonoprazan can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Vonoprazan; Amoxicillin; Clarithromycin: (Major) The need to coadminister methadone with drugs known to prolong the QT interval, such as clarithromycin, should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). In addition, methadone is a substrate for CYP3A4, CYP2D6, and P-glycoprotein (P-gp). Concurrent use of methadone with clarithromycin, an inhibitor of CYP3A4 and P-gp, may result in increased serum concentrations of methadone. (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of vonoprazan is necessary. If vonoprazan is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; vonoprazan is a weak CYP3A and CYP2C19 inhibitor. Concomitant use with vonoprazan can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Voriconazole: (Major) Caution is advised when administering voriconazole with drugs that are known to prolong that QT interval and are metabolized by CYP3A4, such as methadone. If these drugs must be used together, frequent monitoring for adverse events and toxicities related to methadone is recommended; dosage reduction of methadone may be needed. Voriconazole inhibits the primary metabolism of methadone via CYP3A4 inhibition. A clinical study evaluated concurrent use of voriconazole (400 mg PO every 12 hours for 1 day, then 200 mg PO every 12 hours for 4 days) in subjects receiving methadone maintenance dosage (30 to 100 mg PO once daily). Coadministration increased the Cmax and AUC of pharmacologically active R-methadone by 31% and 47%, respectively. In addition, the Cmax and AUC of S-methadone increased by 65% and 103%, respectively. Increased plasma concentrations of methadone have been associated with toxicity including QT prolongation and torsades de pointes, especially at high doses. Voriconazole has been associated with QT prolongation and rare cases of TdP, cardiac arrest, and sudden death. Concurrent use may increase this risk. If these drugs are given together, closely monitor for prolongation of the QT interval. Rigorous attempts to correct any electrolyte abnormalities (i.e., potassium, magnesium, calcium) should be made before initiating concurrent therapy.
Vorinostat: (Major) The need to coadminister methadone with drugs known to prolong the QT interval should be done with extreme caution and a careful assessment of treatment risks versus benefits. Methadone is considered to be associated with an increased risk for QT prolongation and torsades de pointes (TdP), especially at higher doses (> 200 mg/day but averaging approximately 400 mg/day in adult patients). Laboratory studies, both in vivo and in vitro, have demonstrated that methadone inhibits cardiac potassium channels and prolongs the QT interval. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Vorinostat therapy is associated with a risk of QT prolongation and should be used cautiously with methadone.
Vortioxetine: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with vortioxetine. Inform patients taking this combination of the possible increased risks and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Voxelotor: (Moderate) Consider a reduced dose of methadone with frequent monitoring for respiratory depression and sedation if concurrent use of voxelotor is necessary. If voxelotor is discontinued, methadone plasma concentrations can decrease resulting in reduced efficacy and potential withdrawal syndrome in a patient who has developed physical dependence to methadone. Methadone is a substrate of CYP3A, CYP2B6, CYP2C19, CYP2C9, and CYP2D6; voxelotor is a moderate CYP3A inhibitor. Concomitant use with voxelotor can increase methadone exposure resulting in increased or prolonged opioid effects including fatal respiratory depression, particularly when an inhibitor is added to a stable dose of methadone.
Zafirlukast: (Moderate) The concurrent administration of methadone and inhibitors of cytochrome P450 3A4, such as zafirlukast, may result in increased concentrations of methadone. Inhibition of methadone metabolism can lead to toxicity including CNS adverse effects and potential for QT prolongation and torsades de pointes when high doses of methadone are used.
Zaleplon: (Moderate) Concomitant use of methadone with zaleplon can lead to additive respiratory depression, hypotension, profound sedation, or coma. Prior to concurrent use, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of zaleplon. Monitor patients for sedation and respiratory depression.
Ziconotide: (Moderate) Concurrent use of ziconotide and opiate agonists may result in an increased incidence of dizziness and confusion. Ziconotide neither interacts with opiate receptors nor potentiates opiate-induced respiratory depression. However, in animal models, ziconotide did potentiate gastrointestinal motility reduction by opioid agonists.
Zidovudine, ZDV: (Moderate) Methadone increases exposure zidovudine, ZDV. Patients should be monitored for zidovudine toxicity during concurrent methadone treatment; however, the manufacturer of zidovudine states that routine dosage adjustment of zidovudine is not required during coadministration of methadone. Patients who receive both methadone and zidovudine may experience symptoms characteristic of opiate withdrawal and attribute the cause to decreased methadone levels due to zidovudine. However, it is more likely patients are actually experiencing zidovudine side effects due to increased levels since zidovudine has no effect on methadone metabolism. In one pharmacokinetic study (n=9), coadministration of methadone increased the AUC of zidovudine by about 43% (range: 16-64%). It appears methadone inhibits zidovudine glucuronidation and, to a lesser extent, decreases zidovudine renal clearance.
Ziprasidone: (Contraindicated) Ziprasidone is contraindicated with any drugs that list QT prolongation as a pharmacodynamic effect when this effect has been described within the contraindications or bolded or boxed warnings of the official labeling for such drugs, including methadone. QT interval prolongation and serious arrhythmia such as torsade de pointes (TdP) have occurred during treatment with methadone. Most cases involve patients being treated for pain with large, multiple daily doses of methadone, although cases have been reported in patients receiving doses commonly used for maintenance treatment of opioid addiction. Ziprasidone has also been associated with a possible risk for QT prolongation and/or TdP. Both drugs may also cause CNS depression, and this may increase risk for serious respiratory depression from methadone in some patients.
Zolmitriptan: (Moderate) Because of the potential risk and severity of serotonin syndrome, caution should be observed when administering methadone with serotonin-receptor agonists. Inform patients taking this combination of the possible increased risk and monitor for the emergence of serotonin syndrome particularly during treatment initiation and dose adjustment. Discontinue all serotonergic agents and initiate symptomatic treatment if serotonin syndrome occurs.
Zolpidem: (Major) Concomitant use of methadone with zolpidem can lead to additive respiratory depression, hypotension, profound sedation, or coma. In addition, sleep-related behaviors, such as sleep-driving, are more likely to occur during concurrent use of zolpidem and other CNS depressants than with zolpidem alone. Prior to concurrent use, assess the level of tolerance to CNS depression that has developed, the duration of use, and the patient's overall response to treatment. Consider the patient's use of alcohol or illicit drugs. Methadone should be used with caution and in reduced dosages if used concurrently with a CNS depressant; in opioid-naive adults, use an initial methadone dose of 2.5 mg every 12 hours. Also consider a using a lower dose of zolpidem. For Intermezzo brand of sublingual zolpidem tablets, reduce the dose to 1.75 mg/night. Monitor patients for sedation and respiratory depression.
Zonisamide: (Minor) Zonisamide is a weak inhibitor of P-glycoprotein (P-gp), and methadone is a substrate of P-gp. There is theoretical potential for zonisamide to affect the pharmacokinetics of drugs that are P-gp substrates. Use caution when starting or stopping zonisamide or changing the zonisamide dosage in patients also receiving drugs which are P-gp substrates.
How Supplied
Dolophine/Methadone Hydrochloride Intramuscular Inj Sol: 1mL, 10mg
Dolophine/Methadone Hydrochloride Intravenous Inj Sol: 1mL, 10mg
Dolophine/Methadone Hydrochloride Subcutaneous Inj Sol: 1mL, 10mg
Dolophine/Methadone Hydrochloride/Methadose Oral Tab: 5mg, 10mg, 40mg
Methadone Hydrochloride/Methadose Oral Sol: 1mL, 5mg, 5mL, 10mg
Methadone Hydrochloride/Methadose Oral Tab for Susp: 40mg
Maximum Dosage
With appropriate dosage titration, there is no maximum dose of methadone. Safety and efficacy in pediatric patients have not been established; however, methadone is used off-label in these populations.
Mechanism Of Action
Methadone is a potent µ-opiate receptor agonist. Opiate receptors include µ (mu), kappa (kappa), and delta (delta), which have been reclassified by an International Union of Pharmacology subcommittee as OP1 (delta), OP2 (kappa), and OP3 (µ). These receptors are coupled with G-protein (guanine-nucleotide-binding protein) receptors and function as modulators, both positive and negative, of synaptic transmission via G-proteins that activate effector proteins. Opioid-G-protein systems include adenylyl cyclase-cyclic adenosine monophosphate (cAMP) and phospholipase3 C (PLC)-inositol 1,4,5 triphosphate (Ins(1,4,5)P3)-Ca2). The optical isomers of methadone differ in their binding affinities for opiate receptors. The R-isomer of methadone has a higher affinity for µ1 and µ2 receptors than S-methadone or the racemate. It appears that R-methadone has a receptor binding pattern similar to morphine and S-methadone does not contribute to the opioid effects of the racemic methadone. Methadone isomers and the racemate have low affinities for delta and kappa receptors. Methadone is considered a weak serotonin re-uptake inhibitor and has been implicated in serotonin syndrome toxicity reactions.
Opiates do not alter the pain threshold of afferent nerve endings to noxious stimuli, nor do they affect the conductance of impulses along peripheral nerves. Analgesia is mediated through changes in the perception of pain at the spinal cord (µ2-, delta-, kappa-receptors) and higher levels in the CNS (µ1- and kappa3 receptors). There is no ceiling effect of analgesia for opiates. The emotional response to pain is also altered. Opiates close N-type voltage-operated calcium channels (kappa-receptor agonist) and open calcium-dependent inwardly rectifying potassium channels (µ and delta receptor agonist) resulting in hyperpolarization and reduced neuronal excitability. Binding of the opiate stimulates the exchange of guanosine triphosphate (GTP) for guanosine diphosphate (GDP) on the G-protein complex. Binding of GTP leads to a release of the G-protein subunit, which acts on the effector system. In this case of opioid-induced analgesia, the effector system is adenylate cyclase and cAMP located at the inner surface of the plasma membrane. Thus, opiates decrease intracellular cAMP by inhibiting adenylate cyclase that modulates the release of nociceptive neurotransmitters such as substance P, GABA, dopamine, acetylcholine and norepinephrine. Opiates also modulate the endocrine and immune systems. Opiates inhibit the release of vasopressin, somatostatin, insulin and glucagon.
Clinically, stimulation of µ-receptors produces analgesia, euphoria, respiratory depression, miosis, decreased gastrointestinal motility, and physical dependence. Methadone has a blunted euphoric effect due to its long duration of action and slow onset of action. The decreased euphoric effects of methadone make it unattractive as a drug of abuse and an appropriate agent for the management of opiate dependence. During addiction, the functioning of the opiate receptor is altered due to repeated opiate exposure. Methadone treatment normalizes neurologic and endocrine process. Methadone suppresses opiate 'craving' and produces a blockade of the euphoria induced by morphine-like opiate agonists. Miosis is produced by an excitatory action on the autonomic segment of the nucleus of the oculomotor nerve. Respiratory depression is caused by direct action of opiate agonists on respiratory centers in the brain stem. Opiate agonists increase smooth muscle tone in the antral portion of the stomach, the small intestine (especially the duodenum), the large intestine, and the sphincters. Opiate agonists also decrease secretions from the stomach, pancreas, and biliary tract. The combination of effects of opiate agonists on the GI tract results in constipation and delayed digestion. Urinary smooth muscle tone is also increased by opiate agonists. The tone of the bladder detrusor muscle, ureters, and vesical sphincter is increased, which sometimes causes urinary retention.
Several other clinical effects occur with opiate agonists including cough suppression, hypotension, and nausea/vomiting. The antitussive effects of opiate agonists are mediated through direct action on receptors in the cough center of the medulla. Cough suppression can be achieved at lower doses than those required to produce analgesia. Hypotension is possibly due to an increase in histamine release and/or depression of the vasomotor center in the medulla. Induction of nausea and vomiting possibly occurs from direct stimulation of the vestibular system and/or the chemoreceptor trigger zone.
Pharmacokinetics
Methadone may be administered orally, intravenously, subcutaneously, or intramuscularly. It undergoes a distribution phase with a half-life of 2 to 3 hours. Methadone is 85% to 90% bound to alpha-1-acid-glycoprotein. Disease states, such as cancer, and other medications that affect the serum concentrations of alpha-1-acid-glycoprotein may alter patient response. Methadone is widely distributed into tissues due to its basic and lipophilic properties, and is secreted into breast milk. Concentrations in amniotic fluid and cord plasma are proportional to maternal plasma concentrations. Due to slow release from tissue binding sites, prolonged serum concentrations and cumulative effects occur. Steady-state plasma concentrations and full analgesic effects are usually not obtained until days 3 to 5 of dosing. The peak respiratory depressant effects typically occur later and persist longer than its peak analgesic effects, especially during the early dosing period. Depressant effects after overdosage can persist for 36 to 48 hours.
Methadone undergoes N-demethylation in the liver by CYP450 microsomal isoenzymes CYP3A4 (primary), CYP2B6, and CYP2C19 to an inactive metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenypyrrolidine (EDDP); CYP2C9 and CYP2D6 are involved to a lesser degree. With chronic dosing, methadone may induce its own metabolism via CYP3A4. Fecal elimination accounts for the majority of excretion. Urinary excretion of methadone and inactive metabolites, which is considered a minor route, is by glomerular filtration and occurs to a variable degree. Urinary excretion is pH-dependent and increases at urinary pH less than 6. As the pH of the urine decreases, this route of elimination becomes clinically significant. The elimination half-life in adults is 8 to 150 hours. With repeated dosing, methadone is retained in the liver and then slowly released, which extends the duration of potential toxicity. Elimination half-lives as long as 120 hours have been reported in patients receiving repeated doses.
In adults, R-methadone has a significantly longer mean elimination half-life than S-methadone (37.6 hours and 28.6 hours, respectively). Significant differences in mean clearance are also seen. Methadone may exhibit large inter-patient variability in plasma concentrations at the same dose. Trough concentrations more than 200 to 400 ng/mL are usually required to prevent withdrawal symptoms at the end of the dosing interval. Methadone plasma concentrations do not correlate with subjective complaints but do relate to the actual physical manifestations of withdrawal. There is a group of patients who are excessive metabolizers and may require higher than usual doses to remain stable. Pharmacokinetic monitoring of methadone concentrations in these patients may be worthwhile to determine appropriate dosage adjustments.
Affected cytochrome P450 isoenzymes and drug transporters: CYP3A, CYP2B6, CYP2C19, CYP2C9, CYP2D6, P-glycoprotein (P-gp)
Methadone undergoes N-demethylation in the liver by CYP450 microsomal isoenzymes CYP3A4 (primary), CYP2B6, and CYP2C19 to an inactive metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenypyrrolidine (EDDP); CYP2C9 and CYP2D6 are involved to a lesser degree. Concurrent administration with agents that inhibit or induce CYP isoenzymes may affect patient response. Methadone also is a substrate of P-glycoprotein (P-gp); methadone concentrations can be altered by P-gp inhibitors.
Methadone is well-absorbed (36% to 100%) after oral administration, and peak serum concentrations occur 1 to 7.5 hours after a dose. Onset of action occurs within 30 to 60 minutes of oral dose administration. Methadone also undergoes first-pass metabolism in the GI tract where methadone is a substrate for P-glycoprotein. The transport of methadone across the gut wall may be increased in the presence of P-glycoprotein inhibitors.
Intravenous RouteOnset of action occurs within 10 to 20 minutes of parenteral administration. As compared to oral administration intravenous administration results in a higher concentration to dose ratios of R-methadone, the active isomer; this is due to a decreased first-pass effect in the liver and the by-passing of gut metabolism of methadone.
Intramuscular RouteAbsorption after intramuscular administration of methadone has not been well characterized but appears to be unpredictable.
Subcutaneous RouteAbsorption after subcutaneous administration of methadone has not been well characterized but appears to be unpredictable.
Pregnancy And Lactation
Methadone is excreted in breast milk. According to the American Academy of Breastfeeding Medicine and previous American Academy of Pediatrics recommendations, therapeutic methadone use is usually compatible with breast-feeding. Consider the benefits of breast-feeding along with the mother's clinical need for methadone and any potential adverse effects on the breast-fed child from methadone or the underlying maternal condition. Women who received methadone maintenance therapy for opioid dependence during pregnancy who are stable may be encouraged to breast-feed, unless another contraindication (e.g., street drug abuse) is present. Other drugs (e.g., morphine) are preferable for pain control during breast-feeding. At maternal oral doses of 10 to 80 mg/day, methadone concentrations from 50 to 570 mcg/L in milk have been reported. In most samples, the milk concentrations were lower than maternal serum drug concentrations at steady state. Based on an average milk consumption of 150 mL/kg/day, an infant would consume approximately 17.4 mcg/kg/day, which is approximately 2% to 3% of the oral maternal dose. Methadone has been detected in very low plasma concentrations in some infants whose mothers were taking methadone. Although breast-feeding may help mitigate withdrawal symptoms in the neonate, in some cases when methadone maintenance was used during pregnancy, the amount of methadone in breast milk may not be enough to fully avoid withdrawal in the infant. Of 8 breast-fed babies born to women maintained on methadone 50 to 105 mg/day, 1 required pharmacotherapy for neonatal opioid withdrawal syndrome, whereas 4 of 8 formula-fed babies needed treatment for the event. Advise breast-feeding women taking methadone to monitor the infant for increased drowsiness and breathing difficulty. There are rare cases of sedation and respiratory depression in infants exposed to methadone through breast milk.