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DESCRIPTION

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

HOW SUPPLIED

Flomax/Tamsulosin/Tamsulosin Hydrochloride Oral Cap: 0.4mg

DOSAGE & INDICATIONS

For the treatment of the signs and symptoms of benign prostatic hyperplasia (BPH).

Oral dosage

Adults

The recommended dosage is 0.4 mg PO once daily, 30 minutes following a meal. In patients who fail to respond to this dose after 2—4 weeks of therapy, the dose can be increased to 0.8 mg PO once daily. If therapy is interrupted for several days at either the 0.4 mg or 0.8 mg dose, therapy should resume at the 0.4 mg/day dosage. NOTE: Tamsulosin is not indicated for the treatment of hypertension.

Geriatric

See adult dosage. Elderly patients may be more sensitive to the effects of the usual adult dosage. Adjust dosage based on clinical response.

MAXIMUM DOSAGE

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.

DOSING CONSIDERATIONS

Hepatic Impairment

No dosage adjustment is needed in patients with mild to moderate hepatic dysfunction. Tamsulosin has not been studied in patients with severe hepatic impairment. Since tamsulosin is extensively metabolized, it is prudent to start with the lowest initial adult dosage (0.4 mg PO once daily) in liver disease. Monitor and adjust dosage based on clinical response.

Renal Impairment

No dosage adjustment is needed. Patients with renal impairment should be monitored carefully for exaggerated hypotensive effects (e.g., first dose effect).
 
Intermittent hemodialysis:
No dosage adjustment is needed. Tamsulosin is highly protein bound and is not likely to be significantly removed during hemodialysis. However, patients with renal failure should be monitored carefully for exaggerated hypotensive effects (e.g., first dose effect).

ADMINISTRATION

Oral Administration

Per the package label, the capsules should be swallowed whole and not crushed, chewed, or opened. However, the manufacturer indicates that the contents of a capsule (i.e., granules) may theoretically be mixed with a small quantity of acidic fruit juice (e.g., orange, grape) or acidic soft food (e.g., applesauce, yogurt) prior to administration. If tamsulosin is administered via this method, instruct the patient to not chew, crush, or dissolve the granules as these actions may result in rapid drug release and serious side effects.
The effects on drug delivery by 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.
Administer approximately 30 minutes after the same meal each day.

STORAGE

Flomax:
- Protect from moisture
- Store between 68 to 77 degrees F, excursions permitted 59 to 86 degrees F

CONTRAINDICATIONS / PRECAUTIONS

Sulfonamide hypersensitivity

Tamsulosin is a non-arylamine sulfonamide derivative. In patients with sulfonamide hypersensitivity, allergic reaction to tamsulosin has been rarely reported. If a patient reports a serious or life threatening sulfonamide allergy, the manufacturer advises caution when administering tamsulosin. However, tamsulosin is not contraindicated for use in patients with sulfonamide allergy. Based on clinical trials and post-marketing experience with tamsulosin, the potential for cross-reactivity in patients with sulfonamide allergy has not been established. In post-marketing experience, allergic-type reactions (such as skin rash, pruritus, urticaria, and angioedema of the tongue, lips, and face) have been reported in some cases, and, in very rare cases, in patients who had a history of sulfa allergy (manufacturer data on file). According to the manufacturer, clinical trials with tamsulosin did not screen for or exclude patients with a history of sulfonamide allergy; therefore, the actual potential for sulfonamide cross-reactivity with tamsulosin is unknown. Non-arylamine sulfonamide derivatives (e.g., tamsulosin) have been reported to be proposed to have a lower risk of allergic reactions in patients with sulfonamide allergy, presumably due to the lack of one of the proposed structural sites of action for sulfonamide allergy (arylamine group in the N4 position). One large retrospective cohort study has reported that in patients with the presence of an allergic reaction after exposure to a sulfonamide antibiotic, 9.9% had an allergic reaction after receiving a non-antibiotic sulfonamide derivative, and 1.6% of patients who lacked an allergic reaction after sulfonamide antibiotic exposure had an allergic reaction after administration of a non-antibiotic sulfonamide derivative (adjusted odds ratio 2.8; 95% CI, 2.1—3.7). A causal relationship between sulfonamide hypersensitivity and allergic reactions with non-arylamine sulfonamide derivatives has not been definitively established and remains controversial. In general, patients with a documented sulfonamide allergy are considered to be predisposed for development of allergic drug reactions. Until further data are available, caution is prudent when administering sulfonamide derivatives to patients with a documented sulfonamide hypersensitivity.

Orthostatic hypotension, renal disease, renal failure, renal impairment, syncope

Tamsulosin should be used cautiously in patients with orthostatic hypotension, vertigo, or syncope. The signs and symptoms of orthostasis (postural hypotension, dizziness, and vertigo) were more frequently reported in tamsulosin-treated patients than those receiving placebo. As with other alpha-adrenergic blocking agents, there is a potential risk of syncope and patients should be cautioned to avoid situations where injury could result should syncope occur. Patients with renal impairment, renal failure, or other renal disease as well as elderly patients should also be monitored carefully for exaggerated hypotensive effects (e.g., first dose effect).

Prostate cancer

Prostate cancer and benign prostatic hyperplasia (BPH) cause many of the same symptoms and frequently they coexist. Patients should be evaluated prior to starting tamsulosin therapy to rule out the presence of prostate cancer.

Hepatic disease

Tamsulosin has not been studied in patients with severe hepatic impairment. Since tamsulosin is extensively metabolized, cautious dosage initiation at a lower dosage is prudent in patients with severe hepatic disease.

Pregnancy

Tamsulosin is classified pregnancy category B; however, tamsulosin is only indicated to treat benign prostatic hyperplasia in men and is not used for females.

Breast-feeding

Tamsulosin is only used to treat benign prostatic hyperplasia in men and is not indicated for breast-feeding women.

Children

Tamsulosin is not indicated for use in children.

Ocular surgery

Patients receiving or who have previously received treatment with tamsulosin or other alpha-1 blockers may be at risk for intraoperative floppy iris syndrome (IFIS) during surgery for cataracts (ocular surgery). Intraoperative floppy iris syndrome is a small pupil syndrome variant that is characterized by a flaccid iris that billows in response to intraoperative irrigation currents, progressive intraoperative miosis despite preoperative dilation with standard mydriatic drugs, and potential prolapse of the iris toward the phacoemulsification incisions. IFIS may increase the risk of eye complications during and after surgery. Ophthalmologists should be prepared for possible modifications to their surgical technique such as the use of iris hooks, iris dilator rings, or viscoelastic substances. The benefit of stopping alpha-1 blocker therapy prior to cataract surgery has not been established. However, it is recommended to avoid initiation of new therapy with tamsulosin in patients scheduled for cataract surgery.

Priapism

Rarely (probably less than 1 in 50,000), tamsulosin, like other alpha adrenergic antagonists, has been associated with priapism (persistent painful penile erection unrelated to sexual activity). Priapism, if not treated promptly, can result in irreversible damage to the erectile tissue. Patients who have an erection lasting greater than 4 hours, whether painful or not, should seek emergency medical attention.

Geriatric

Tamsulosin can cause orthostatic hypotension with accompanying dizziness or vertigo. Geriatric patients should be monitored carefully for exaggerated hypotensive effects (e.g., first dose effect). The federal Omnibus Budget Reconciliation Act (OBRA) regulates medication use in residents of long-term care facilities (LTCFs). According to the OBRA guidelines, assessment of the underlying causes and identification of the type/category of urinary incontinence needs to be documented prior to or soon after the time of initiating treatment with a urinary incontinence medication. These medications have specific and limited indications based on the cause and categorization of incontinence. Patients should be assessed periodically for medication effects on urinary incontinence as well as lower urinary tract symptoms and treatment tolerability.

ADVERSE REACTIONS

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 (unspecified) / 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

DRUG INTERACTIONS

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; 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; Phenyltoloxamine: (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 when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
Acetaminophen; Propoxyphene: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of propoxyphene. 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 propoxyphene, should be avoided.
Alfuzosin: (Severe) The pharmacokinetic and pharmacodynamic interactions between alfuzosin 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, therefore, alfuzosin should not be administered in combination with other alpha-blockers.
Aliskiren; 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.
Aliskiren; 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.
Alpha-blockers: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
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: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of amiodarone. 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 amiodarone, should be avoided.
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; Hydrochlorothiazide, HCTZ; 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; Hydrochlorothiazide, HCTZ; 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; 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; Telmisartan: (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.
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; Lansoprazole: (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.
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.
Amphetamine; Dextroamphetamine Salts: (Major) Amphetamines increase both systolic and diastolic blood pressure and may counteract the activity of some antihypertensive agents. Due to the risk of unopposed alpha-adrenergic activity, amphetamines should be used cautiously with beta-blockers. Increased blood pressure, bradycardia, or heart block may occur due to excessive alpha-adrenergic receptor stimulation. In particular, amphetamines can inhibit the antihypertensive response to guanadrel, an adrenergic antagonist that causes depletion of norepinephrine in the synapse. Close monitoring of blood pressure or the selection of alternative therapeutic agents may be needed.
Amprenavir: (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.
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) 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. (Moderate) The plasma concentrations of tamsulosin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as hypotension, is recommended during coadministration. Cobicistat is a CYP3A4 and CYP2D6 inhibitor, while tamsulosin is a CYP3A4 and CYP2D6 substrate.
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: (Major) Since the symptoms of orthostasis (e.g., postural hypotension, dizziness and vertigo) are reported more frequently in tamsulosin-treated vs. placebo patients, there is a theoretical risk of enhanced hypotensive effects in individual patients when tamsulosin co-administered with vasodilatory agents such as phosphodiesterase inhibitors. Concurrent use of PDE5 inhibitors and alpha-blockers may lead to symptomatic hypotension in some patients. When sildenafil (25 mg) was simultaneously administered with doxazosin (4 mg) to patients with BPH, mean additional reductions in supine blood pressure of 7 mmHg systolic and 7 mmHg diastolic were observed. When higher doses of sildenafil were administered with doxazosin (4 mg), symptomatic postural hypotension within 1 to 4 hours was reported in some patients. Sildenafil doses greater than 25 mg should not be taken within 4 hours of taking alpha-blockers. The manufacturers for tadalafil and vardenafil state that patients should be stabilized on alpha blocker therapy prior to starting either tadalafil or vardenafil, or if already receiving optimum dose of tadalafil or vardenafil, alpha blocker therapy should be started at the lowest possible dose.
Bendroflumethiazide; 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
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
Boceprevir: (Severe) The concurrent use of tamsulosin and boceprevir is contraindicated due to the potential for serious/life-threatening reactions. Tamsulosin is metabolized by the hepatic isoenzyme CYP3A4; boceprevir inhibits this isoenzyme. Coadministration may result in elevated tamsulosin plasma concentrations, which could cause adverse events such as hypotension and priapism.
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 when administering tamsulosin with a strong CYP2D6 inhibitor such as bupropion. 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.
Bupropion; Naltrexone: (Moderate) Use caution when administering tamsulosin with a strong CYP2D6 inhibitor such as bupropion. 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.
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.
Carbetapentane; 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.
Carbetapentane; 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.
Carbetapentane; Diphenhydramine; Phenylephrine: (Moderate) Use caution when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
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: (Moderate) Monitor for tamsulosin-related adverse reactions if coadministration with ceritinib is necessary; the risk may higher if the patient is also taking a CYP2D6 inhibitor. Ceritinib is a CYP3A4 inhibitor and tamsulosin is primarily metabolized by CYP3A4. Coadministration with a strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by 2.2-fold and 2.8-fold, respectively; the effects of concomitant administration of a moderate CYP3A4 inhibitor have not been evaluated. The degree of CYP3A4 inhibition by ceritinib is unknown.
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; 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; Dihydrocodeine; 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; Guaifenesin; Hydrocodone; 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; 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; Hydrocodone; 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; 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) Cimetidine is a weak inhibitor of CYP2D6, one of the enzymes responsible for metabolism of tamsulosin. The manufacturer recommends that tamsulosin be used with caution in combination with cimetidine. A study involving 10 healthy volunteers (age range 21 to 40 years) showed that cimetidine administered at the highest recommended dose (400 mg q6h for 6 days) significantly (26%) decreased the clearance of a single tamsulosin 0.4 mg dose. This resulted in a moderate increase in tamsulosin AUC (44%).
Cinacalcet: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as cinacalcet. 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.
Citalopram: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as citalopram. 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.
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: (Moderate) The plasma concentrations of tamsulosin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as hypotension, is recommended during coadministration. Cobicistat is a CYP3A4 and CYP2D6 inhibitor, while tamsulosin is a CYP3A4 and CYP2D6 substrate.
Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Alafenamide: (Moderate) The plasma concentrations of tamsulosin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as hypotension, is recommended during coadministration. Cobicistat is a CYP3A4 and CYP2D6 inhibitor, while tamsulosin is a CYP3A4 and CYP2D6 substrate.
Cobicistat; Elvitegravir; Emtricitabine; Tenofovir Disoproxil Fumarate: (Moderate) The plasma concentrations of tamsulosin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as hypotension, is recommended during coadministration. Cobicistat is a CYP3A4 and CYP2D6 inhibitor, while tamsulosin is a CYP3A4 and CYP2D6 substrate.
Codeine; Phenylephrine; Promethazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as promethazine. 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.
Codeine; Promethazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as promethazine. 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.
Conivaptan: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of conivaptan. 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 conivaptan, should be avoided.
Crizotinib: (Moderate) Monitor for an increase in tamsulosin-related adverse reactions, including hypotension, if coadministration with crizotinib is necessary. 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.
Dalfopristin; Quinupristin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of dalfopristin; quinupristin. 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 quinupristin, should be avoided.
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.
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) 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. (Moderate) The plasma concentrations of tamsulosin may be elevated when administered concurrently with cobicistat. Clinical monitoring for adverse effects, such as hypotension, is recommended during coadministration. Cobicistat is a CYP3A4 and CYP2D6 inhibitor, while tamsulosin is a CYP3A4 and CYP2D6 substrate.
Dasabuvir; Ombitasvir; Paritaprevir; 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.
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; Diphenhydramine; Phenylephrine: (Moderate) Use caution when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
Dextromethorphan; Promethazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as promethazine. 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.
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 when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
Diphenhydramine; Hydrocodone; Phenylephrine: (Moderate) Use caution when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
Diphenhydramine; Ibuprofen: (Moderate) Use caution when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
Diphenhydramine; Naproxen: (Moderate) Use caution when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
Diphenhydramine; Phenylephrine: (Moderate) Use caution when administering tamsulosin with moderate CYP2D6 inhibitors. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4. Diphenhydramine is a CYP2D6 inhibitor; consider if another antihistamine would be appropriate to treat the patient's symptoms. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. Interactions with moderate CYP2D6 inhibitors have not been evaluated. The effects of co-administration of both a CYP3A4 and a CYP2D6 inhibitor with tamsulosin have also not been evaluated. However, there is a potential for significant increase in tamsulosin exposure when tamsulosin is co-administered with a combination of both CYP3A4 and CYP2D6 inhibitors. If concomitant use in necessary, monitor patient closely for increased side effects.
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: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
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.
Drospirenone; Ethinyl Estradiol: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Drospirenone; Ethinyl Estradiol; Levomefolate: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Duloxetine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as duloxetine. 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.
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.
Enalapril; 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.
Erythromycin: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as erythromycin. 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.
Erythromycin; Sulfisoxazole: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as erythromycin. 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.
Escitalopram: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as escitalopram. 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.
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
Ethanol: (Moderate) Ethanol interacts with antihypertensive agents by potentiating their hypotensive effect.
Ethinyl Estradiol: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Desogestrel: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Ethynodiol Diacetate: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Etonogestrel: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Levonorgestrel: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Levonorgestrel; Folic Acid; Levomefolate: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Norelgestromin: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Norethindrone Acetate: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Norethindrone Acetate; Ferrous fumarate: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Norethindrone: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Norethindrone; Ferrous fumarate: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Norgestimate: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
Ethinyl Estradiol; Norgestrel: (Moderate) Tamsulosin is metabolized by CYP3A4. Ethinyl Estradiol, which inhibits CYP3A4, may cause increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with ethinyl estradiol.
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.
Fluconazole: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as fluconazole. 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.
Fluoxetine: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of fluoxetine. 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 fluoxetine, should be avoided.
Fluoxetine; Olanzapine: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of fluoxetine. 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 fluoxetine, should be avoided.
Fluvoxamine: (Moderate) Hepatic cytochrome P450 enzymes 2D6 and 3A4 are responsible for the extensive metabolism of tamsulosin. Fluvoxamine, which inhibits both CYP2D6 and CYP3A4, may cause significant increases in tamsulosin plasma concentrations. Although no clinical studies have been done, tamsulosin should be used cautiously with fluvoxamine.
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.
Gefitinib: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as gefitinib. 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.
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).
Halofantrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as halofantrine. 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.
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.
Hydrochlorothiazide, HCTZ; 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
Hydrochlorothiazide, HCTZ; 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
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, STI-571: (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.
Isoniazid, INH: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of isoniazid, INH. 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. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as isoniazid, should be avoided.
Isoniazid, INH; Pyrazinamide, PZA; Rifampin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of isoniazid, INH. 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. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as isoniazid, should be avoided.
Isoniazid, INH; Rifampin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of isoniazid, INH. 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. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as isoniazid, should be avoided.
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) Avoid concurrent use and use of tamsulosin for up to 2 weeks after discontinuation of itraconazole treatment unless benefits of treatment outweigh the potentially increased risk of side effects. 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.
Ivacaftor: (Minor) Use caution when administering ivacaftor and tamsulosin concurrently. Ivacaftor is an inhibitor of CYP3A and tamsulosin is partially metabolized by CYP3A. Co-administration can theoretically increase tamsulosin exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Ketoconazole: (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.
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
Levobetaxolol: (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
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
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.
Lumacaftor; Ivacaftor: (Minor) Use caution when administering ivacaftor and tamsulosin concurrently. Ivacaftor is an inhibitor of CYP3A and tamsulosin is partially metabolized by CYP3A. Co-administration can theoretically increase tamsulosin exposure leading to increased or prolonged therapeutic effects and adverse events; however, the clinical impact of this has not yet been determined.
Meperidine; Promethazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as promethazine. 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.
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
Mifepristone, RU-486: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as mifepristone, RU-486. 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.
Mirabegron: (Minor) The effect of mirabegron on tamsulosin pharmacokinetics was determined in drug interaction studies. Although no dose adjustment is recommended with tamsulosin treatment based on the lack of pharmacokinetic interaction, mirabegron should be administered with caution in patients taking other medications in the setting of urinary obstruction because of the risk of urinary retention.
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, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
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.
Ombitasvir; Paritaprevir; 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.
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 when administering tamsulosin with a strong CYP2D6 inhibitor such as paroxetine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with paroxetine resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively. If concomitant use in necessary, monitor patient closely for increased side effects.
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.
Penbutolol: (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
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: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
Phentolamine: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
Phenylephrine; Promethazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as promethazine. 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.
Phosphodiesterase inhibitors: (Major) Since the symptoms of orthostasis (e.g., postural hypotension, dizziness and vertigo) are reported more frequently in tamsulosin-treated vs. placebo patients, there is a theoretical risk of enhanced hypotensive effects in individual patients when tamsulosin co-administered with vasodilatory agents such as phosphodiesterase inhibitors. Concurrent use of PDE5 inhibitors and alpha-blockers may lead to symptomatic hypotension in some patients. When sildenafil (25 mg) was simultaneously administered with doxazosin (4 mg) to patients with BPH, mean additional reductions in supine blood pressure of 7 mmHg systolic and 7 mmHg diastolic were observed. When higher doses of sildenafil were administered with doxazosin (4 mg), symptomatic postural hypotension within 1 to 4 hours was reported in some patients. Sildenafil doses greater than 25 mg should not be taken within 4 hours of taking alpha-blockers. The manufacturers for tadalafil and vardenafil state that patients should be stabilized on alpha blocker therapy prior to starting either tadalafil or vardenafil, or if already receiving optimum dose of tadalafil or vardenafil, alpha blocker therapy should be started at the lowest possible dose.
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: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
Promethazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as promethazine. 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.
Propafenone: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as propafenone. 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.
Propoxyphene: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of propoxyphene. 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 propoxyphene, should be avoided.
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
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: (Moderate) Use caution if coadministration of ribociclib 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 increase in treatment-related adverse reactions including hypotension, dizziness, and vertigo. Ribociclib is a moderate CYP3A4 inhibitor and tamsulosin is a CYP3A4 substrate. The effect of concomitant use of a moderate CYP3A4 inhibitor with tamsulosin has not been evaluated; however, administration with a strong CYP3A4 inhibitor significantly increased the AUC and Cmax of tamsulosin.
Ribociclib; Letrozole: (Moderate) Use caution if coadministration of ribociclib 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 increase in treatment-related adverse reactions including hypotension, dizziness, and vertigo. Ribociclib is a moderate CYP3A4 inhibitor and tamsulosin is a CYP3A4 substrate. The effect of concomitant use of a moderate CYP3A4 inhibitor with tamsulosin has not been evaluated; however, administration with a strong CYP3A4 inhibitor significantly increased the AUC and Cmax of tamsulosin.
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.
Sertraline: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as sertraline. 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.
Sildenafil: (Major) Since the symptoms of orthostasis (e.g., postural hypotension, dizziness and vertigo) are reported more frequently in tamsulosin-treated vs. placebo patients, there is a theoretical risk of enhanced hypotensive effects in individual patients when tamsulosin co-administered with vasodilatory agents such as phosphodiesterase inhibitors. Concurrent use of PDE5 inhibitors and alpha-blockers may lead to symptomatic hypotension in some patients. When sildenafil (25 mg) was simultaneously administered with doxazosin (4 mg) to patients with BPH, mean additional reductions in supine blood pressure of 7 mmHg systolic and 7 mmHg diastolic were observed. When higher doses of sildenafil were administered with doxazosin (4 mg), symptomatic postural hypotension within 1 to 4 hours was reported in some patients. Sildenafil doses greater than 25 mg should not be taken within 4 hours of taking alpha-blockers. The manufacturers for tadalafil and vardenafil state that patients should be stabilized on alpha blocker therapy prior to starting either tadalafil or vardenafil, or if already receiving optimum dose of tadalafil or vardenafil, alpha blocker therapy should be started at the lowest possible dose.
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.
Simeprevir: (Moderate) Simeprevir, a mild intestinal CYP3A4 inhibitor, may increase the side effects of tamsulosin, which is a CYP3A4 substrate. Monitor patients for adverse effects of tamsulosin, such as hypotension, dizziness, syncope, and vertigo.
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
Streptogramins: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of dalfopristin; quinupristin. 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 quinupristin, should be avoided.
Tadalafil: (Major) Since the symptoms of orthostasis (e.g., postural hypotension, dizziness and vertigo) are reported more frequently in tamsulosin-treated vs. placebo patients, there is a theoretical risk of enhanced hypotensive effects in individual patients when tamsulosin co-administered with vasodilatory agents such as phosphodiesterase inhibitors. Concurrent use of PDE5 inhibitors and alpha-blockers may lead to symptomatic hypotension in some patients. When sildenafil (25 mg) was simultaneously administered with doxazosin (4 mg) to patients with BPH, mean additional reductions in supine blood pressure of 7 mmHg systolic and 7 mmHg diastolic were observed. When higher doses of sildenafil were administered with doxazosin (4 mg), symptomatic postural hypotension within 1 to 4 hours was reported in some patients. Sildenafil doses greater than 25 mg should not be taken within 4 hours of taking alpha-blockers. The manufacturers for tadalafil and vardenafil state that patients should be stabilized on alpha blocker therapy prior to starting either tadalafil or vardenafil, or if already receiving optimum dose of tadalafil or vardenafil, alpha blocker therapy should be started at the lowest possible dose.
Telaprevir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of telaprevir. 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 telaprevir, should be avoided.
Telithromycin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of telithromycin. 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 telithromycin, should be avoided.
Telotristat Ethyl: (Moderate) Use caution if coadministration of telotristat ethyl and tamsulosin is necessary, as the systemic exposure of tamsulosin may be decreased resulting in reduced efficacy. If these drugs are used together, monitor patients for suboptimal efficacy of tamsulosin; consider increasing the dose of tamsulosin if necessary. Tamsulosin is a CYP3A4 substrate. The mean Cmax and AUC of another sensitive CYP3A4 substrate was decreased by 25% and 48%, respectively, when coadministered with telotristat ethyl; the mechanism of this interaction appears to be that telotristat ethyl increases the glucuronidation of the CYP3A4 substrate.
Terazosin: (Severe) Tamsulosin should not be adminsitered in combination with other alpha-blockers.
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.
Vardenafil: (Major) Since the symptoms of orthostasis (e.g., postural hypotension, dizziness and vertigo) are reported more frequently in tamsulosin-treated vs. placebo patients, there is a theoretical risk of enhanced hypotensive effects in individual patients when tamsulosin co-administered with vasodilatory agents such as phosphodiesterase inhibitors. Concurrent use of PDE5 inhibitors and alpha-blockers may lead to symptomatic hypotension in some patients. When sildenafil (25 mg) was simultaneously administered with doxazosin (4 mg) to patients with BPH, mean additional reductions in supine blood pressure of 7 mmHg systolic and 7 mmHg diastolic were observed. When higher doses of sildenafil were administered with doxazosin (4 mg), symptomatic postural hypotension within 1 to 4 hours was reported in some patients. Sildenafil doses greater than 25 mg should not be taken within 4 hours of taking alpha-blockers. The manufacturers for tadalafil and vardenafil state that patients should be stabilized on alpha blocker therapy prior to starting either tadalafil or vardenafil, or if already receiving optimum dose of tadalafil or vardenafil, alpha blocker therapy should be started at the lowest possible dose.
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.
Voriconazole: (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.
Warfarin: (Moderate) The manufacturer reports that results from limited in vitro and in vivo drug-drug interaction studies between tamsulosin and warfarin have been inconclusive; and therefore, tamsulosin should be used cautiously with warfarin.
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.
Zileuton: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as zileuton. 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.

PREGNANCY AND LACTATION

Pregnancy

Tamsulosin is classified pregnancy category B; however, tamsulosin is only indicated to treat benign prostatic hyperplasia in men and is not used for females.

Tamsulosin is only used to treat benign prostatic hyperplasia in men and is not indicated for breast-feeding women.

MECHANISM OF ACTION

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.

PHARMACOKINETICS

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.


Source: http://www.pdr.net/drug-summary/Flomax-tamsulosin-hydrochloride-2893


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