Myambutol

Other Agents for Tuberculosis

 
Tuberculosis
Directly observed therapy (DOT) is recommended for all children as well as adolescents and adults living with HIV and any regimen consisting of intermittent therapy.[34361] [34362] [61094]

May administer with food.
Tablets may be crushed and mixed with apple juice or applesauce.

anaphylactoid reactions / Rapid / 0-1.0
optic neuritis / Delayed / Incidence not known
visual impairment / Early / Incidence not known
erythema multiforme / Delayed / Incidence not known
myocarditis / Delayed / Incidence not known
exfoliative dermatitis / Delayed / Incidence not known
pericarditis / Delayed / Incidence not known
eosinophilic pneumonia / Delayed / Incidence not known

scotomata / Delayed / Incidence not known
blurred vision / Early / Incidence not known
hepatitis / Delayed / Incidence not known
peripheral neuropathy / Delayed / Incidence not known
confusion / Early / Incidence not known
hallucinations / Early / Incidence not known
thrombocytopenia / Delayed / Incidence not known
neutropenia / Delayed / Incidence not known
leukopenia / Delayed / Incidence not known
lymphadenopathy / Delayed / Incidence not known
pneumonitis / Delayed / Incidence not known
gout / Delayed / Incidence not known
hyperuricemia / Delayed / Incidence not known

nausea / Early / Incidence not known
vomiting / Early / Incidence not known
abdominal pain / Early / Incidence not known
anorexia / Delayed / Incidence not known
arthralgia / Delayed / Incidence not known
headache / Early / Incidence not known
dizziness / Early / Incidence not known
fever / Early / Incidence not known
malaise / Early / Incidence not known
pruritus / Rapid / Incidence not known
rash / Early / Incidence not known

Myambutol

Rx

Used for mycobacterial infections including tuberculosis and atypical mycobacterial infections. First-line antituberculosis agent in combination with isoniazid, pyrazinamide, rifampin, and/or streptomycin. Appears to be more effective and less toxic than other antitubercular agents.

15 mg/kg/dose (Max: 1.5 g/dose) PO once daily.[28263] Ethambutol is generally recommended as part of the initial 2-month intensive phase of treatment as first-line therapy.[61094] [65619]

25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily. Ethambutol is generally recommended as part of the initial 2-month intensive phase of treatment as first-line therapy.

1.6 g PO once daily or 5 days/week, or alternatively, 2.4 g PO 3 days/week or 4 g PO twice weekly.[61094] The FDA-approved dose is 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy.[28263] Daily dosing is preferred and is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.[61094] [65619]

1.2 g PO once daily or 5 days/week, or alternatively, 2 g PO 3 days/week or 2.8 g PO twice weekly.[61094] The FDA-approved dose is 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy.[28263] Daily dosing is preferred and is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.[61094] [65619]

800 mg PO once daily or 5 days/week, or alternatively, 1.2 g PO 3 days/week or 2 g PO twice weekly.[61094] The FDA-approved dose is 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy.[28263] Daily dosing is preferred and is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.[61094] [65619]

15 to 25 mg/kg/dose (lean body weight) (Max: 1.6 g/dose) PO once daily or 5 days/week, or alternatively, 50 mg/kg/dose (lean body weight) PO 3 days/week (Max: 2.4 g/dose) or twice weekly (Max: 4 g/dose).[61094] The FDA-approved dose is 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (lean body weight) (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy. Daily dosing is preferred and is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.

15 to 25 mg/kg/dose (lean body weight) (Max: 1.6 g/dose) PO once daily or 5 days/week, or alternatively, 50 mg/kg/dose (lean body weight) PO 3 days/week (Max: 2.4 g/dose) or twice weekly (Max: 4 g/dose).[61094] Daily dosing is preferred and is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.

15 to 25 mg/kg/dose PO once daily. Although tuberculosis is rare in neonates, congenital and postnatal cases have been successfully treated with antitubercular agents. Ethambutol is rarely recommended as part of the initial 2-month intensive phase of treatment due to the potential for optic neuritis and red-green color blindness.[53484] [53485] [61095] [65675]

1.6 g PO once daily. Monitor response and consider therapeutic drug monitoring to assure dosing adequacy. The FDA-approved dose is 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.

1.6 g PO once daily or 5 days/week.[34362] [61094] The FDA-approved dose is 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy.[28263] Daily dosing is defined as 5- or 7 days/week.[61094] Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.[34362] [61094] [65619]

1.2 g PO once daily or 5 days/week. [61094] The FDA-approved dose is 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy. Daily dosing is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.

800 mg PO once daily or 5 days/week. [61094] The FDA-approved dose is 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy. Daily dosing is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.

15 to 25 mg/kg/dose (lean body weight) (Max: 1.6 g/dose) PO once daily or 5 days/week. [61094] The FDA-approved dose is 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (lean body weight) (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy. Ethambutol is generally recommended as part of the initial 2-month intensive phase of treatment as first-line therapy.

15 to 25 mg/kg/dose (lean body weight) (Max: 1.6 g/dose) PO once daily or 5 days/week. [61094] Daily dosing is defined as 5- or 7 days/week. Ethambutol is generally recommended as part of the initial 2-month intensive phase as first-line therapy.

15 to 25 mg/kg/dose PO once daily. Although tuberculosis is rare in neonates, congenital and postnatal cases have been successfully treated with antitubercular agents. Ethambutol is rarely recommended as part of the initial 2-month intensive phase due to the potential for optic neuritis and red-green color blindness.[53484]

15 to 25 mg/kg/dose (lean body weight) PO once daily. The FDA-approved dose is 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (lean body weight) (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy.

15 to 25 mg/kg/dose (lean body weight) PO once daily.   The FDA-approved dose is 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in treatment-naive patients and 25 mg/kg/dose (lean body weight) (Max: 2.5 g/dose) PO once daily for 60 days, then 15 mg/kg/dose (lean body weight) (Max: 1.5 g/dose) PO once daily in patients who have previously received therapy.

15 to 25 mg/kg/dose (lean body weight) PO once daily.

15 mg/kg/dose PO once daily plus clarithromycin or azithromycin. May consider addition of third or fourth drug (rifabutin, amikacin, streptomycin, levofloxacin, or moxifloxacin) for patients with high mycobacterial loads (more than 2 log CFU/mL of blood) or in the absence of effective antiretroviral therapy. Duration of treatment depends on clinical response but should continue for at least 12 months.[34362]

15 mg/kg/dose PO once daily plus clarithromycin or azithromycin. May consider addition of third or fourth drug (rifabutin, amikacin, streptomycin, levofloxacin, or moxifloxacin) for patients with high mycobacterial loads (more than 2 log CFU/mL of blood) or in the absence of effective antiretroviral therapy. Duration of treatment depends on clinical response but should continue for at least 12 months.[34362]

15 to 25 mg/kg/dose PO once daily (Max: 2.5 g/day) plus clarithromycin or azithromycin. For severe disease, consider adding rifabutin. If rifabutin cannot be administered or if a fourth drug is needed for patients with more severe symptoms or disseminated disease, consider adding ciprofloxacin, levofloxacin, or amikacin. Duration of treatment depends on clinical response but should continue for at least 12 months.[34361]

15 mg/kg/dose PO once daily plus clarithromycin or azithromycin. May consider addition of third or fourth drug (rifabutin, amikacin, streptomycin, levofloxacin, or moxifloxacin) for patients with high mycobacterial loads (more than 2 log CFU/mL of blood) or in the absence of effective antiretroviral therapy. Consider discontinuing secondary prophylaxis in patients who have completed at least 12 months of MAC treatment, have no signs or symptoms of MAC, and have a sustained (more than 6 months) CD4 count more than 100 cells/mm3 in response to ART. Restart secondary prophylaxis if the CD4 count decreases to less than 100 cells/mm3.[34362]

15 mg/kg/dose PO once daily plus clarithromycin or azithromycin. May consider addition of third or fourth drug (rifabutin, amikacin, streptomycin, levofloxacin, or moxifloxacin) for patients with high mycobacterial loads (more than 2 log CFU/mL of blood) or in the absence of effective antiretroviral therapy. Consider discontinuing secondary prophylaxis in patients who have completed at least 12 months of MAC treatment, have no signs or symptoms of MAC, and have a sustained (more than 6 months) CD4 count more than 100 cells/mm3 in response to ART. Restart secondary prophylaxis if the CD4 count decreases to less than 100 cells/mm3.[34362]

15 to 25 mg/kg/dose PO once daily (Max: 2.5 g/day) plus clarithromycin or azithromycin with rifabutin for children older than 5 years who received rifabutin as part of initial treatment. Do not discontinue secondary prophylaxis for children younger than 2 years. Consider discontinuing secondary prophylaxis in children older than 2 years who have received at least 12 months of MAC treatment, have no signs or symptoms of MAC, have been receiving stable antiretroviral therapy, and have a sustained (more than 6 months) CD4 count more than 200 cells/mm3 for children 2 to 5 years and more than 100 cells/mm3 for children 6 years and older. Restart secondary prophylaxis if the CD4 count falls below these thresholds.[34361]

†Indicates off-label use

Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed.

Reduce ethambutol dose in patients with renal impairment, since the main path of excretion of this drug is by the kidneys.[28263]
 
Adult patients† [34362] [61094] [65465]
CrCl 30 mL/minute or more: No dosage adjustment needed.
CrCl less than 30 mL/minute: 15 to 25 mg/kg/dose PO 3 days/week. Consider therapeutic drug monitoring to guide optimal dosing.
 
Pediatric patients† [32569]
GFR 30 mL/minute/1.73 m3 or more: No dosage adjustment needed
GFR 10 to 29 mL/minute/1.73 m3: 15 to 25 mg/kg/dose PO every 36 hours.
GFR less than 10 mL/minute/1.73 m3: 15 to 25 mg/kg/dose PO every 48 hours.
 
Intermittent hemodialysis†
Adult patients† [34362] [61094]
15 to 25 mg/kg/dose PO 3 days/week after hemodialysis. Consider therapeutic drug monitoring to guide optimal dosing.
 
Pediatric patients† [32569]
15 to 25 mg/kg/dose PO every 48 hours.
 
Peritoneal dialysis†
Adult patients† [32569]
15 to 25 mg/kg/dose PO every 48 hours.
 
Pediatric patients† [32569]
15 to 25 mg/kg/dose PO every 48 hours.
 
Continuous renal replacement therapy (CRRT)†NOTE: Various CRRT modalities include continuous venovenous hemofiltration (CVVH), continuous venovenous hemodialysis (CVVHD), continuous venovenous hemodiafiltration (CVVHDF), continuous venovenous high-flux hemodialysis (CVVHFD), continuous arteriovenous hemofiltration (CAVH), continuous arteriovenous hemodialysis (CAVHD), and continuous arteriovenous hemodiafiltration (CAVHDF). Dosing should take into consideration patient-specific factors (e.g., intrinsic renal function), type of infection, the duration of renal replacement therapy, the effluent flow rate, and the replacement solution administered.[42303]
 
Adult patients† [32569]
15 to 25 mg/kg/dose PO every 24 to 36 hours.
 
Pediatric patients† [32569]
No dosage adjustment needed.

Aluminum Hydroxide: (Moderate) Aluminum hydroxide can reduce the rate or extent of ethambutol absorption. At least 4 hours should elapse between doses of aluminum hydroxide-containing antacids and ethambutol.
Aluminum Hydroxide; Magnesium Carbonate: (Moderate) Aluminum hydroxide can reduce the rate or extent of ethambutol absorption. At least 4 hours should elapse between doses of aluminum hydroxide-containing antacids and ethambutol.
Aluminum Hydroxide; Magnesium Hydroxide: (Moderate) Aluminum hydroxide can reduce the rate or extent of ethambutol absorption. At least 4 hours should elapse between doses of aluminum hydroxide-containing antacids and ethambutol.
Aluminum Hydroxide; Magnesium Hydroxide; Simethicone: (Moderate) Aluminum hydroxide can reduce the rate or extent of ethambutol absorption. At least 4 hours should elapse between doses of aluminum hydroxide-containing antacids and ethambutol.
Aluminum Hydroxide; Magnesium Trisilicate: (Moderate) Aluminum hydroxide can reduce the rate or extent of ethambutol absorption. At least 4 hours should elapse between doses of aluminum hydroxide-containing antacids and ethambutol.
Aminosalicylate sodium, Aminosalicylic acid: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of aminosalicylate sodium, aminosalicylic acid and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs may be used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Bacillus Calmette-Guerin Vaccine, BCG: (Major) Urinary concentrations of ethambutol could interfere with the therapeutic effectiveness of BCG. Postpone instillation of BCG if the patient is receiving antibiotics.
Capreomycin: (Moderate) Adverse hepatic effects have been associated with capreomycin, especially with concurrent use of other antituberculosis drugs known to alter hepatic function. Theoretically, coadministration of capreomycin and ethambutol could increase the risk of hepatotoxicity. Monitor patients for changes in liver function if these drugs are coadministered.
Ethionamide: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of ethionamide and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs may be used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Isoniazid, INH: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of ethambutol and isoniazid, INH. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of ethambutol and isoniazid, INH. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program. (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of pyrazinamide, PZA and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program. (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of rifampin and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Isoniazid, INH; Rifampin: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of ethambutol and isoniazid, INH. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program. (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of rifampin and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Omeprazole; Amoxicillin; Rifabutin: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of rifabutin and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Probenecid: (Moderate) Probenecid has uricosuric actions. Ethambutol can also cause hyperuricemia. Although this effect represents a pharmacodynamic interaction, dosage adjustments of probenecid may be necessary if ethambutol is administered to patients being treated with probenecid.
Probenecid; Colchicine: (Moderate) Probenecid has uricosuric actions. Ethambutol can also cause hyperuricemia. Although this effect represents a pharmacodynamic interaction, dosage adjustments of probenecid may be necessary if ethambutol is administered to patients being treated with probenecid.
Pyrazinamide, PZA: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of pyrazinamide, PZA and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Rifabutin: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of rifabutin and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Rifampin: (Moderate) Careful monitoring of hepatic function is recommended with the concurrent use of rifampin and ethambutol. Each drug has the potential to cause hepatotoxicity, and hepatotoxicity risk may be increased with concomitant use. These drugs are often used together for the treatment of active tuberculosis (TB) infection, and patients should also be assessed for additional risk factors for hepatotoxicity, such as other hepatotoxic drugs, alcohol use, and underlying hepatic disease. Any adverse event leading to hospitalization or death should be reported to local or state health departments as well as the FDA MedWatch program.
Vigabatrin: (Major) Vigabatrin should not be used with ethambutol, which is associated with serious ophthalmic effects (e.g., retinopathy or glaucoma) unless the benefit of treatment clearly outweighs the risks.

Ethambutol/Ethambutol Hydrochloride/Myambutol Oral Tab: 100mg, 400mg

Dosing is based on lean body weight.

25 mg/kg/dose (Max: 2.5 g/dose) PO once daily is the FDA-approved maximum dosage. Other regimens and maximum dosages have been used off-label.
Weighing more than 90 kg: 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily.
Weighing 76 to 90 kg: 1.6 g PO once daily or 5 days/week, 2.4 g PO 3 days/week, or 4 g PO twice weekly.
Weighing 56 to 75 kg: 1.2 g PO once daily or 5 days/week, 2 g PO 3 days/week, or 2.8 g PO twice weekly.
Weighing 40 to 55 kg: 800 mg PO once daily or 5 days/week, 1.2 g PO 3 days/week, or 2 g PO twice weekly.

25 mg/kg/dose (Max: 2.5 g/dose) PO once daily is the FDA-approved maximum dosage. Other regimens and maximum dosages have been used off-label.
Weighing more than 90 kg: 25 mg/kg/dose (Max: 2.5 g/dose) PO once daily.
Weighing 76 to 90 kg: 1.6 g PO once daily or 5 days/week, 2.4 g PO 3 days/week, or 4 g PO twice weekly.
Weighing 56 to 75 kg: 1.2 g PO once daily or 5 days/week, 2 g PO 3 days/week, or 2.8 g PO twice weekly.
Weighing 40 to 55 kg: 800 mg PO once daily or 5 days/week, 1.2 g PO 3 days/week, or 2 g PO twice weekly.

25 mg/kg/dose (Max: 2.5 g/dose) PO once daily is the FDA-approved maximum dose. 25 mg/kg/dose (Max: 1.6 g/dose) PO once daily or 5 days/week or 50 mg/kg/dose PO 3 days/week (Max: 2.4 g/dose) or twice weekly (Max: 4 g/dose) has been used off-label.

Safety and efficacy have not been established. 25 mg/kg/dose (Max: 1.6 g) PO once daily or 5 days/week or 50 mg/kg/dose PO 3 days/week (Max: 2.4 g/dose) or twice weekly (Max: 4 g/dose) has been used off-label.

Safety and efficacy have not been established. 25 mg/kg/dose PO once daily or 5 days/week or 50 mg/kg/dose PO 3 days/week or twice weekly has been used off-label.

Safety and efficacy have not been established. 25 mg/kg/dose PO once daily has been used off-label.

Ethambutol is primarily bacteriostatic, although in higher doses it also exhibits bactericidal properties. The exact mechanism is not known; however, it appears to inhibit RNA synthesis, resulting in impaired cellular metabolism and multiplication. Ethambutol is effective only against bacilli that are actively dividing. Cross-resistance between ethambutol and other antitubercular agents has not been demonstrated.
 
In general, the following organisms are susceptible to ethambutol: M. tuberculosis; M. bovis; M. marinum; and some strains of M. kansasii, M. avium, M. fortuitum, and M. intracellulare.

Ethambutol is administered orally. Ethambutol is widely distributed, with high concentrations in the kidneys, lungs, and saliva. It penetrates inflamed meninges (10—50%) to reach therapeutic levels in the CSF. The drug crosses the placenta, resulting in plasma fetal concentrations that are 30% of maternal concentrations, and is distributed into breast milk in amounts similar to maternal plasma levels. Ethambutol is partially metabolized in the liver. The parent drug and its metabolites are excreted primarily in the urine (65%), with the remaining 20—25% excreted unchanged in the feces. The elimination half-life is 3.5 hours and can be up to 15 hours in renal disease.

Approximately 75—80% of an ethambutol oral dose is absorbed. Peak serum levels are attained within 2—4 hours.

Use ethambutol during pregnancy only if the benefit justifies the potential risk to the fetus. There are no adequate and well-controlled studies of ethambutol use in pregnant women. There are reports of ophthalmic abnormalities occurring in infants born to women on antituberculosis therapy that included ethambutol. Ethambutol has been shown to be teratogenic in animal studies when given in high doses. Tuberculosis guidelines support treatment initiation in pregnancy whenever the probability of maternal disease is moderate to high due to the risk of untreated tuberculosis to a pregnant woman and her fetus.

Use ethambutol during breast-feeding only if the expected benefit to the mother outweighs the potential risk to the fetus. Ethambutol is distributed into human breast milk.[28263] Previous American Academy of Pediatrics recommendations considered ethambutol to be usually compatible with breast-feeding.[27500] Tuberculosis guidelines encourage breast-feeding for women who are noninfectious and being treated with first-line agents, such as ethambutol, as the small concentrations of these drugs measured in breast milk have not been reported to produce toxic effects in the nursing infant.[61094]