Flomax

Alpha-Blockers

Oral Administration

Administer approximately 30 minutes after the same meal each day.[29677]
Per the package label, the capsules should be swallowed whole and not crushed, chewed, or opened.[29677] However, trials with pediatric patients have reported that the capsules were opened if the patient had difficulty swallowing or if the prescribed dosage required. The contents of a capsule (i.e., granules) were mixed with cool, soft food (e.g., yogurt or pudding) or with juice.[64293] [64294] If tamsulosin is administered via this method, instruct the patient not to chew, crush, or dissolve the granules as these actions may result in rapid drug release and serious side effects.[29677]
The administration of tamsulosin through nasogastric, gastric, or jejunostomy tubes has not been formally evaluated by the manufacturer; reports suggest that the granules may adhere to the sides of the tube, which complicates administration and increases the risk of tube blockage.[52913]

Severe

Stevens-Johnson syndrome / Delayed / Incidence not known
exfoliative dermatitis / Delayed / Incidence not known
angioedema / Rapid / Incidence not known
erythema multiforme / Delayed / Incidence not known
atrial fibrillation / Early / Incidence not known
arrhythmia exacerbation / Early / Incidence not known
visual impairment / Early / Incidence not known

Moderate

ejaculation dysfunction / Delayed / 8.4-18.1
chest pain (unspecified) / Early / 4.0-4.1
blurred vision / Early / 0.2-2.0
orthostatic hypotension / Delayed / 0.2-0.4
priapism / Early / 0-0.1
dyspnea / Early / Incidence not known
palpitations / Early / Incidence not known
sinus tachycardia / Rapid / Incidence not known
hypotension / Rapid / Incidence not known
constipation / Delayed / Incidence not known
floppy iris syndrome / Delayed / Incidence not known

Mild

headache / Early / 19.3-21.1
rhinitis / Early / 13.1-17.9
dizziness / Early / 14.9-17.1
infection / Delayed / 9.0-10.8
asthenia / Delayed / 7.8-8.5
back pain / Delayed / 7.0-8.3
rash / Early / 2.0-7.0
diarrhea / Early / 4.3-6.2
pharyngitis / Delayed / 5.1-5.8
cough / Delayed / 3.4-4.5
drowsiness / Early / 3.0-4.3
nausea / Early / 2.6-3.9
sinusitis / Delayed / 2.2-3.7
insomnia / Early / 1.4-2.4
libido decrease / Delayed / 1.0-2.0
vertigo / Early / 0.6-1.0
syncope / Early / 0.2-0.6
epistaxis / Delayed / Incidence not known
pruritus / Rapid / Incidence not known
urticaria / Rapid / Incidence not known
vomiting / Early / Incidence not known
xerostomia / Early / Incidence not known

Flomax

Rx

Oral alpha-blocker; used once-daily for BPH; may cause less hypotension than other alpha-blockers due to specificity for prostate alpha-receptors.

For the treatment of benign prostatic hyperplasia (BPH). Oral dosage Adults

0.4 mg PO once daily, initially. May increase the dose to 0.8 mg PO once daily after 2 to 4 weeks based on clinical response. If therapy is interrupted for several days, restart at 0.4 mg PO once daily.

For medical expulsive treatment (MET) as an adjunct to conservative management of distal uretal nephrolithiasis†. Oral dosage Adults

Adults with radiopaque lower ureteral stones of 10 mm or smaller have received tamsulosin 0.4 mg PO at bedtime for 28 days or until definite stone passage (i.e., evidence of stone on urine straining) in addition to standard analgesia (e.g., NSAID, etc.) in clinical studies. Data suggest that patients receiving tamsulosin for medical expulsive therapy (MET) with stones of 5 to 10 mm pass the stones earlier and with less pain than if no tamsulosin is received; thus, MET may be considered in these patients. Tamsulosin may offer little benefit over placebo for patients with stones of less than 5 mm.

Children and Adolescents

Pediatric patients with radiopaque lower ureteral stones of 10 or 12 mm or smaller have received the following doses: tamsulosin 0.4 mg PO at bedtime for children older than 4 years and 0.2 mg PO at bedtime for children 4 years or younger, given for 28 days or until definite stone passage (i.e., evidence of stone on urine straining). Tamsulosin is given in addition to standard analgesia (e.g., ibuprofen). Most patients receiving tamsulosin pass stones earlier and with less pain than if no tamsulosin is received. Mild somnolence is common. In children, if pain is controlled with oral analgesia, clear liquids are tolerated, and there is no evidence of infection, they are closely monitored for spontaneous passage for 3 to 4 weeks prior to definitive therapy, since most data demonstrate safe lower uretal stone expulsion in the first 10 days of conservative medical management.

†Indicates off-label use

Hepatic Impairment

Mild to moderate hepatic impairment (Child Pugh Class A or B): No dosage adjustment is needed.
Severe hepatic impairment (Child Pugh Class C): No dosage recommendations are available. Tamsulosin has not been studied in patients with severe hepatic impairment.

Renal Impairment

No dosage adjustment is needed. Patients with renal impairment should be monitored carefully for exaggerated hypotensive effects (e.g., first dose effect). Patients with end-stage renal disease (CrCl less than 10 mL/minute/1.73 m2) have not been specifically studied.
 
Intermittent hemodialysis:
No dosage adjustment appears to be needed. Patients with renal impairment should be monitored carefully for exaggerated hypotensive effects (e.g., first dose effect). Tamsulosin is highly protein bound and is not likely to be significantly removed during hemodialysis. Patients with end-stage renal disease (CrCl less than 10 mL/minute/1.73 m2) have not been specifically studied.

Abiraterone: (Moderate) Monitor for an increase in tamsulosin-related adverse reactions if coadministration with abiraterone is necessary. Tamsulosin is a CYP2D6 substrate and abiraterone is a moderate CYP2D6 inhibitor. The effects of coadministration with a moderate CYP2D6 on the pharmacokinetics of tamsulosin have not been evaluated; however, the manufacturer of tamsulosin recommends caution with use.
Acebutolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Acetaminophen; Aspirin; Diphenhydramine: (Moderate) Use caution if coadministration of diphenhydramine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and diphenhydramine is a moderate CYP2D6 inhibitor.
Acetaminophen; Chlorpheniramine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Acetaminophen; Chlorpheniramine; Dextromethorphan: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Acetaminophen; Chlorpheniramine; Phenylephrine : (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Acetaminophen; Diphenhydramine: (Moderate) Use caution if coadministration of diphenhydramine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and diphenhydramine is a moderate CYP2D6 inhibitor.
Adagrasib: (Major) Concurrent use of tamsulosin and adagrasib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A and CYP2D6 substrate and adagrasib is a strong CYP3A and moderate CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A inhibitor increased the AUC of tamsulosin by 2.8-fold.
Alpha-blockers: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
Ambrisentan: (Minor) Because symptoms of orthostasis (e.g., postural hypotension, dizziness, vertigo) are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Amiodarone: (Moderate) Use caution if coadministration of amiodarone with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 and CYP2D6 substrate and amiodarone is a moderate CYP3A4 and CYP2D6 inhibitor. The effects of concomitant administration of a moderate CYP3A4 and CYP2D6 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 and CYP2D6 inhibition.
Amlodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Amlodipine; Atorvastatin: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Amlodipine; Benazepril: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Amlodipine; Celecoxib: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Amlodipine; Olmesartan: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Amlodipine; Valsartan: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Amlodipine; Valsartan; Hydrochlorothiazide, HCTZ: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Amobarbital: (Moderate) Concurrent use of amobarbital with antihypertensive agents may lead to hypotension. Monitor for decreases in blood pressure during times of coadministration.
Amoxicillin; Clarithromycin; Omeprazole: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of clarithromycin. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as clarithromycin, should be avoided.
Aprepitant, Fosaprepitant: (Moderate) Use caution if tamsulosin and aprepitant, fosaprepitant are used concurrently and monitor for an increase in tamsulosin-related adverse effects for several days after administration of a multi-day aprepitant regimen. Tamsulosin 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 tamsulosin. 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.
Artemether; Lumefantrine: (Moderate) Use caution when administering tamsulosin with a strong CYP2D6 inhibitor such as artemether; lumefantrine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure. If concomitant use in necessary, monitor patient closely for increased side effects.
Atazanavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Atazanavir; Cobicistat: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Atenolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Atenolol; Chlorthalidone: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Avanafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of avanafil. Conversely, patients already receiving an optimized dose of avanafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of avanafil and tamsulosin.
Berotralstat: (Moderate) Use caution if coadministration of berotralstat with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg. The systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 and CYP2D6 substrate and berotralstat is a moderate CYP3A4 and CYP2D6 inhibitor. The effects of concomitant administration of a moderate CYP3A4/CYP2D6 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 inhibition.
Beta-blockers: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Betaxolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Bisoprolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Bisoprolol; Hydrochlorothiazide, HCTZ: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Brimonidine; Timolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Bupropion: (Moderate) Use caution if coadministration of bupropion with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and bupropion is a strong CYP2D6 inhibitor. Concomitant treatment with another strong CYP2D6 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
Bupropion; Naltrexone: (Moderate) Use caution if coadministration of bupropion with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and bupropion is a strong CYP2D6 inhibitor. Concomitant treatment with another strong CYP2D6 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
Calcium-channel blockers: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Carteolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Carvedilol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Ceritinib: (Major) Concurrent use of tamsulosin and ceritinib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 like ceritinib are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Chloramphenicol: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as chloramphenicol. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure; interactions with moderate CYP3A4 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Codeine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Dextromethorphan: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Hydrocodone: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Ibuprofen; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpheniramine; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Chlorpromazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpromazine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Cimetidine: (Moderate) Use caution if coadministration of cimetidine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Treatment with cimetidine 400 mg every 6 hours for 6 days in healthy volunteers (n = 10) resulted in a 26% decrease in the clearance of tamsulosin, which resulted in a 44% increase in tamsulosin AUC. Tamsulosin is a CYP2D6 and CYP3A substrate and cimetidine is a weak CYP2D6 and CYP3A inhibitor.
Cinacalcet: (Moderate) Use caution if coadministration of cinacalcet with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and cinacalcet is a moderate CYP2D6 inhibitor.
Clarithromycin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of clarithromycin. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as clarithromycin, should be avoided.
Clevidipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Cobicistat: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Conivaptan: (Moderate) Use caution if coadministration of conivaptan with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A substrate and conivaptan is a moderate CYP3A inhibitor.
Crizotinib: (Moderate) Use caution if coadministration of crizotinib with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 substrate and crizotinib is a moderate CYP3A4 inhibitor. The effects of concomitant administration of a moderate CYP3A4 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 inhibition.
Cyclosporine: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as cyclosporine. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure; interactions with moderate CYP3A4 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Dacomitinib: (Moderate) Use caution if coadministration of dacomitinib with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and dacomitinib is a strong CYP2D6 inhibitor. Concomitant treatment with another strong CYP2D6 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
Danazol: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as danazol. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure; interactions with moderate CYP3A4 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Darifenacin: (Moderate) Use caution if coadministration of darifenacin with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and darifenacin is a moderate CYP2D6 inhibitor. The effects of concomitant administration of a moderate CYP2D6 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP2D6 inhibition.
Darunavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Darunavir; Cobicistat: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Darunavir; Cobicistat; Emtricitabine; Tenofovir alafenamide: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Delavirdine: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of delavirdine. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as delavirdine, should be avoided.
Dextromethorphan; Bupropion: (Moderate) Use caution if coadministration of bupropion with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and bupropion is a strong CYP2D6 inhibitor. Concomitant treatment with another strong CYP2D6 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
Dextromethorphan; Diphenhydramine; Phenylephrine: (Moderate) Use caution if coadministration of diphenhydramine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and diphenhydramine is a moderate CYP2D6 inhibitor.
Dextromethorphan; Quinidine: (Moderate) Use caution when administering tamsulosin with a strong CYP2D6 inhibitor such as quinidine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure. If concomitant use in necessary, monitor patient closely for increased side effects.
Diltiazem: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Diphenhydramine: (Moderate) Use caution if coadministration of diphenhydramine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and diphenhydramine is a moderate CYP2D6 inhibitor.
Diphenhydramine; Ibuprofen: (Moderate) Use caution if coadministration of diphenhydramine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and diphenhydramine is a moderate CYP2D6 inhibitor.
Diphenhydramine; Naproxen: (Moderate) Use caution if coadministration of diphenhydramine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and diphenhydramine is a moderate CYP2D6 inhibitor.
Diphenhydramine; Phenylephrine: (Moderate) Use caution if coadministration of diphenhydramine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and diphenhydramine is a moderate CYP2D6 inhibitor.
Dorzolamide; Timolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Doxazosin: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
Dronedarone: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of dronedarone. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as dronedarone, should be avoided.
Duloxetine: (Moderate) Use caution if coadministration of duloxetine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and duloxetine is a moderate CYP2D6 inhibitor.
Elbasvir; Grazoprevir: (Moderate) Administering tamsulosin with elbasvir; grazoprevir may result in elevated tamsulosin plasma concentrations. Tamsulosin is a substrate of CYP3A; grazoprevir is a weak CYP3A inhibitor. If these drugs are used together, closely monitor for signs of adverse events.
Eliglustat: (Moderate) Coadministration of tamsulosin and eliglustat may result in increased concentrations of tamsulosin. Use tamsulosin with caution in patients receiving eliglustat, particularly if the tamsulosin dose is greater than 0.4 mg, and monitor closely for tamsulosin-related adverse effects including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 and CYP3A4 substrate; eliglustat is a CYP2D6 inhibitor.
Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Alafenamide: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Disoproxil Fumarate: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Erythromycin: (Moderate) Use caution if coadministration of erythromycin with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A substrate and erythromycin is a moderate CYP3A inhibitor.
Escitalopram: (Moderate) Use caution if coadministration of escitalopram with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and escitalopram is a moderate CYP2D6 inhibitor.
Esmolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Everolimus: (Moderate) Monitor for an increase in tamsulosin-related adverse reactions if coadministration with everolimus is necessary. Tamsulosin is a CYP3A4 and CYP2D6 substrate. Everolimus is a weak CYP3A4 inhibitor and a CYP2D6 inhibitor. The effects of coadministration of both a CYP3A4 and CYP2D6 inhibitor with tamsulosin have not been evaluated; however, there is a potential for significantly increased plasma concentrations of tamsulosin.
Fedratinib: (Moderate) Use caution if coadministration of fedratinib with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 and CYP2D6 substrate and fedratinib is a moderate CYP3A4 and CYP2D6 inhibitor. The effects of concomitant administration of moderate CYP3A4 and moderate CYP2D6 inhibitors on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 and CYP2D6 inhibition.
Felodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Finasteride; Tadalafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest recommended dose of tadalafil. Conversely, patients already receiving an optimized dose of tadalafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. When tadalafil is used for benign prostatic hypertrophy (BPH), discontinue tamsulosin therapy at least 1 day prior to initiating tadalafil therapy. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of tadalafil and tamsulosin.
Fluconazole: (Moderate) Use caution if coadministration of fluconazole with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A substrate and fluconazole is a moderate CYP3A inhibitor.
Fluoxetine: (Moderate) Use caution if coadministration of fluoxetine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and fluoxetine is a strong CYP2D6 inhibitor. Concomitant treatment with another strong CYP2D6 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
Fluvoxamine: (Moderate) Tamsulosin should be used with caution in combination with moderate inhibitors of CYP3A4 such as fluvoxamine. The cytochrome P450 enzymes CYP3A4 and CYP2D6 are responsible for the extensive metabolism of tamsulosin. Strong inhibitors of CYP3A4 are known to increase the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. No studies have been performed with moderate CYP3A4 inhibitors. As with other alpha adrenergic blocking agents there is a potential risk of syncope with tamsulosin, particularly if serum concentrations are elevated. Monitor blood pressure and observe for symptoms of orthostasis.
Fosamprenavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Grapefruit juice: (Moderate) Hepatic cytochrome P450 enzymes 2D6 and 3A4 are responsible for the extensive metabolism of tamsulosin. Although no clinical studies have been done, tamsulosin should be used with caution with inhibitors of CYP3A4 isoenzymes (e.g., grapefruit juice).
Haloperidol: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as haloperidol. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Idelalisib: (Major) Avoid concomitant use of idelalisib, a strong CYP3A inhibitor, with tamsulosin, a CYP3A substrate, as tamsulosin toxicities may be significantly increased. The AUC of a sensitive CYP3A substrate was increased 5.4-fold when coadministered with idelalisib.
Iloprost: (Minor) Iloprost can have additive effects when administered with other antihypertensive agents, including alpha-blockers. These effects can be used to therapeutic advantage, but dosage adjustments may be necessary.
Imatinib: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of imatinib, STI-571. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as imatinib, STI-571, should be avoided.
Indinavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Isavuconazonium: (Moderate) The plasma concentrations of tamsulosin may be elevated when administered concurrently with isavuconazonium. Clinical monitoring for adverse effects, such as hypotension, is recommended during coadministration. Tamsulosin is a substrate of the hepatic isoenzyme CYP3A4 and drug transporter P-glycoprotein (P-gp); isavuconazole, the active moiety of isavuconazonium, is an inhibitor of CYP3A4 and P-gp.
Isradipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Itraconazole: (Major) Use of tamsulosin is not recommended during and for 2 weeks after itraconazole therapy due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Ketoconazole: (Major) Concurrent use of tamsulosin and ketoconazole is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations are expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4. Coadministration with ketoconazole, a strong CYP3A4 inhibitor, increased the Cmax and AUC of tamsulosin 2.2 and 2.8-fold, respectively.
Labetalol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Lansoprazole; Amoxicillin; Clarithromycin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of clarithromycin. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as clarithromycin, should be avoided.
Lefamulin: (Moderate) Use caution if coadministration of oral lefamulin with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 substrate and oral lefamulin is a moderate CYP3A4 inhibitor; an interaction is not expected with intravenous lefamulin. The effects of concomitant administration of a moderate CYP3A4 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 inhibition.
Lenacapavir: (Moderate) Use caution if coadministration of lenacapavir with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A substrate and lenacapavir is a moderate CYP3A inhibitor.
Letermovir: (Moderate) An increase in the plasma concentration of tamsulosin may occur when given with letermovir. Avoid this combination in patients who are also receiving treatment with cyclosporine because the magnitude of this interaction may be amplified. Tamsulosin is partially metabolized by CYP3A4. Letermovir is a moderate CYP3A4 inhibitor; however, when given with cyclosporine, the combined effect on CYP3A4 substrates is similar to a strong CYP3A4 inhibitor. In a drug interaction study, concomitant use of tamsulosin with another strong CYP3A4 inhibitor resulted in increase in the maximum plasma concentration and exposure of tamsulosin by a factor of 2.2 and 2.8, respectively. The effects of concurrent use with moderate CYP3A4 inhibitors have not been evaluated.
Levamlodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Levobunolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Levoketoconazole: (Major) Concurrent use of tamsulosin and ketoconazole is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations are expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4. Coadministration with ketoconazole, a strong CYP3A4 inhibitor, increased the Cmax and AUC of tamsulosin 2.2 and 2.8-fold, respectively.
Lonafarnib: (Major) Avoid concurrent use of tamsulosin and lonafarnib due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4, and strong inhibitors of CYP3A4, such as lonafarnib, are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Lopinavir; Ritonavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Metoprolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Metoprolol; Hydrochlorothiazide, HCTZ: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Mifepristone: (Major) Concurrent use of tamsulosin and mifepristone is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A, and strong inhibitors of CYP3A, such as mifepristone, are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Mirabegron: (Moderate) The effect of mirabegron on tamsulosin pharmacokinetics was determined in drug interaction studies, there was a lack of pharmacokinetic interaction. However, it is recommended that mirabegron be administered with caution in patients taking other medications in the setting of risks for urinary obstruction because of the risk of urinary retention. This includes caution when used with tamsulosin. In addition, mirabegron is a moderate CYP2D6 inhibitor. Exposure of drugs metabolized by CYP2D6 isoenzymes such as tamsulosin may be increased when co-administered with mirabegron.
Mitotane: (Moderate) Use caution if mitotane and tamsulosin are used concomitantly, and monitor for decreased efficacy of tamsulosin and a possible change in dosage requirements. Mitotane is a strong CYP3A4 inducer and tamsulosin is a CYP3A4 substrate; coadministration may result in decreased plasma concentrations of tamsulosin.
Nadolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Nebivolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Nebivolol; Valsartan: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Nefazodone: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of nefazodone. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as nefazodone, should be avoided.
Nelfinavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Nicardipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Nifedipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Nimodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicard

ipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Niraparib; Abiraterone: (Moderate) Monitor for an increase in tamsulosin-related adverse reactions if coadministration with abiraterone is necessary. Tamsulosin is a CYP2D6 substrate and abiraterone is a moderate CYP2D6 inhibitor. The effects of coadministration with a moderate CYP2D6 on the pharmacokinetics of tamsulosin have not been evaluated; however, the manufacturer of tamsulosin recommends caution with use.
Nirmatrelvir; Ritonavir: (Major) Consider withholding tamsulosin, if clinically appropriate, during receipt of ritonavir-boosted nirmatrelvir. If this is not feasible, consider using an alternative COVID-19 therapy or reducing the tamsulosin dose for patients receiving a dose of 0.8 mg daily. Coadministration may increase tamsulosin exposure resulting in increased hypotension or orthostasis. Tamsulosin is a CYP3A substrate and nirmatrelvir is a CYP3A inhibitor. (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Nisoldipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Olanzapine; Fluoxetine: (Moderate) Use caution if coadministration of fluoxetine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and fluoxetine is a strong CYP2D6 inhibitor. Concomitant treatment with another strong CYP2D6 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
Olmesartan; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Oritavancin: (Minor) Tamsulosin is metabolized by CYP3A4 and CYP2D6; oritavancin is a weak CYP3A4 and CYP2D6 inducer. Plasma concentrations and efficacy of tamsulosin may be reduced if these drugs are administered concurrently.
Paroxetine: (Moderate) Use caution if coadministration of paroxetine with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and paroxetine is a strong CYP2D6 inhibitor. Concomitant treatment with paroxetine increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
Pazopanib: (Moderate) Pazopanib is a weak inhibitor of CYP3A4. Coadministration of pazopanib and tamsulosin, a CYP3A4 substrate, may cause an increase in systemic concentrations of tamsulosin. Use caution when administering these drugs concomitantly.
Peginterferon Alfa-2b: (Minor) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as peginterferon alfa-2b. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Perindopril; Amlodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Perphenazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as perphenazine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Perphenazine; Amitriptyline: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as perphenazine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Phenoxybenzamine: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
Phentolamine: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
Pindolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Posaconazole: (Major) Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Plasma concentrations of tamsulosin are increased with concomitant use of ketoconazole, a strong inhibitor of CYP3A4. Concomitant treatment with ketoconazole resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as ketoconazole, itraconazole, posaconazole, or voriconazole should be avoided.
Prazosin: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
Propafenone: (Moderate) Use caution if coadministration of propafenone with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and propafenone is a moderate CYP2D6 inhibitor.
Propranolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Propranolol; Hydrochlorothiazide, HCTZ: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Protease inhibitors: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Quinidine: (Moderate) Use caution when administering tamsulosin with a strong CYP2D6 inhibitor such as quinidine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure. If concomitant use in necessary, monitor patient closely for increased side effects.
Quinine: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of quinine. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as quinine, should be avoided.
Ranolazine: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of ranolazine. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as ranolazine, should be avoided.
Ribociclib: (Major) Concurrent use of tamsulosin and ribociclib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Ribociclib; Letrozole: (Major) Concurrent use of tamsulosin and ribociclib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Ritlecitinib: (Moderate) Use caution if coadministration of ritlecitinib with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A substrate and ritlecitinib is a moderate CYP3A inhibitor.
Ritonavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Rolapitant: (Major) Use caution if tamsulosin and rolapitant are used concurrently, and monitor for tamsulosin-related adverse effects. Tamsulosin is a CYP2D6 substrate and rolapitant is a moderate CYP2D6 inhibitor; the inhibitory effect of rolapitant lasts for at least 7 days, and may last longer after single dose administration. The Cmax and AUC of another CYP2D6 substrate, dextromethorphan, were increased by 120% and 160%, respectively, on day 1 with rolapitant, and by 180% and 230%, respectively, on day 8 after rolapitant administration.
Saquinavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Sildenafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and tamsulosin.
Silodosin: (Major) The pharmacodynamic effects of coadministration of silodosin and other alpha-blockers has not been studied. Additive effects on blood pressure or an increased incidence of adverse reactions common to alpha-blocker treatment is possible. Therefore, combined use of silodosin and other alpha-blockers is not recommended.
Sotalol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Tadalafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest recommended dose of tadalafil. Conversely, patients already receiving an optimized dose of tadalafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. When tadalafil is used for benign prostatic hypertrophy (BPH), discontinue tamsulosin therapy at least 1 day prior to initiating tadalafil therapy. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of tadalafil and tamsulosin.
Telmisartan; Amlodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Terazosin: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
Terbinafine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as terbinafine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Thioridazine: (Moderate) Use caution when administering tamsulosin with a CYP2D6 inhibitor such as thioridazine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
Timolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
Tipranavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
Trandolapril; Verapamil: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Tucatinib: (Major) Concurrent use of tamsulosin and tucatinib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4, and strong inhibitors of CYP3A4, such as tucatinib, are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Vardenafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of vardenafil. Conversely, patients already receiving an optimized dose of vardenafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of vardenafil and tamsulosin.
Vemurafenib: (Moderate) Vemurafenib is an inducer of CYP3A4 and decreased plasma concentrations of drugs metabolized by this enzyme, such as tamsulosin, could be expected with concurrent use. Use caution, and monitor therapeutic effects of tamsulosin when coadministered with vemurafenib.
Verapamil: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
Vonoprazan; Amoxicillin; Clarithromycin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of clarithromycin. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as clarithromycin, should be avoided.
Voriconazole: (Major) Concurrent use of tamsulosin and voriconazole is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
Voxelotor: (Moderate) Use caution if coadministration of voxelotor with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A substrate and voxelotor is a moderate CYP3A inhibitor. The effects of concomitant administration of a moderate CYP3A inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A inhibition.
Zafirlukast: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as zafirlukast. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure; interactions with moderate CYP3A4 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.

Flomax/Tamsulosin/Tamsulosin Hydrochloride Oral Cap: 0.4mg

Adults

0.8 mg/day PO.

Elderly

0.8 mg/day PO.

Adolescents

Safety and efficacy have not been established.

Children

Safety and efficacy have not been established.

Mechanism of Action: Tamsulosin is a selective antagonist at alpha-1-receptors. Alpha-1-receptors are involved in contraction of smooth muscle and are abundant in the prostate, prostatic capsule, prostatic urethra, and bladder neck. Three subtypes of alpha-1-receptors have been identified: Alpha-1a, alpha-1b, and alpha-1d. Alpha-1a receptors mediate human prostatic smooth muscle contraction whereas alpha-1b and alpha-1d-receptors are involved in vascular smooth muscle contraction. Both alpha-1a and alpha-1b-receptors exist in the prostate, however, approximately 70% of the alpha-receptors in the human prostate are of the alpha-1a subtype. Tamsulosin has 7—38-fold greater affinity for alpha-1a-receptors than for alpha-1b-receptors. Blockade of these receptors by tamsulosin can cause smooth muscles in the bladder neck and prostate to relax, thereby improving urine flow rate and reducing symptoms of BPH.

Tamsulosin is administered orally.  In the systemic circulation, it is extensively bound to plasma proteins (94% to 99%), primarily to alpha1-acid glycoprotein (AAG). Tamsulosin is metabolized by CYP2D6 and CYP3A4. Metabolites undergo extensive conjugation to glucuronide or sulfate prior to excretion in the urine. Less than 10% of the dose is excreted unchanged in the urine. The elimination half-life of tamsulosin in normal volunteers is 14.9 +/- 3.9 hours.
 
Affected cytochrome P450 isoenzymes and drug transporters:  CYP2D6, CYP3A4
Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes.

Oral Route

Following oral administration, tamsulosin is almost completely (> 90%) absorbed under fasting conditions. However, taking tamsulosin in a fasted state results in a 30% increase in bioavailability and a 40—70% increase in Cmax compared to taking tamsulosin after a meal. Taking tamsulosin on an empty stomach could potentially increase the risk of some side effects (i.e., orthostasis); therefore tamsulosin should be taken with food. The time to maximum concentration is roughly 6—7 hours under fed conditions.

Pregnancy

Tamsulosin is only approved by the FDA to treat benign prostatic hyperplasia in men. Tamsulosin is not indicated for use in women and there are no adequate data on the developmental risks associated with the use of tamsulosin during human pregnancy. Animals studies have not revealed adverse developmental effects; however, animal studies are not always predictive of human response.

Tamsulosin is only approved by the FDA to treat benign prostatic hyperplasia in men. Tamsulosin is not indicated in women, and there are no data on the use of tamsulosin in breast-feeding women. There are no data regarding the presence or absence of tamsulosin in human milk, the effects of tamsulosin on the breastfed infant, or the effects on milk production.[29677]