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  • CLASSES

    Alpha-Blockers

    DEA CLASS

    Rx

    DESCRIPTION

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

    COMMON BRAND NAMES

    Flomax

    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
    Adult males

    The recommended dosage is 0.4 mg PO once daily, 30 minutes following a meal and given at approximately the same time each day. In patients who fail to respond to this dose after 2 to 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. LIMITATION OF USE: Tamsulosin is not indicated for the treatment of hypertension.

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

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

    Children and Adolescents

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

    †Indicates off-label use

    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

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

    Renal Impairment

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

    ADMINISTRATION

    Oral Administration

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

    STORAGE

    Flomax:
    - Protect from moisture
    - Store at 77 degrees F; excursions permitted to 59-86 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 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. Elderly patients and patients with renal impairment or renal failure should 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 only approved by the FDA to treat benign prostatic hyperplasia in men. Tamsulosin is not indicated for use in women and there are no adequate data on the developmental risks associated with the use of tamsulosin during human pregnancy. Animals studies have not revealed adverse developmental effects; however, animal studies are not always predictive of human response.

    Breast-feeding

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

    Children, infants

    Tamsulosin is only FDA-approved to treat benign prostatic hyperplasia in men; the drug is not FDA-approved for use in children. There are limited clinical data regarding use in pediatric patients for off-label purposes; use with caution. There are no data describing tamsulosin use in infants.

    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 / 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

    Abiraterone: (Moderate) Monitor for an increase in tamsulosin-related adverse reactions if coadministration with abiraterone is necessary. Tamsulosin is a CYP2D6 substrate and abiraterone is a moderate CYP2D6 inhibitor. The effects of coadministration with a moderate CYP2D6 on the pharmacokinetics of tamsulosin have not been evaluated; however, the manufacturer of tamsulosin recommends caution with use.
    Acebutolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Acetaminophen; Chlorpheniramine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Acetaminophen; Chlorpheniramine; Dextromethorphan: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Acetaminophen; Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Acetaminophen; Chlorpheniramine; Phenylephrine : (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Acetaminophen; 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.
    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: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
    Ambrisentan: (Minor) Because symptoms of orthostasis (e.g., postural hypotension, dizziness, vertigo) are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents.
    Amiodarone: (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; Celecoxib: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Amlodipine; Olmesartan: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Amlodipine; Valsartan: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Amlodipine; Valsartan; Hydrochlorothiazide, HCTZ: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Amobarbital: (Moderate) Concurrent use of amobarbital with antihypertensive agents may lead to hypotension. Monitor for decreases in blood pressure during times of coadministration.
    Amoxicillin; Clarithromycin; Omeprazole: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of clarithromycin. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as clarithromycin, should be avoided.
    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) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Atenolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Atenolol; Chlorthalidone: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Avanafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of avanafil. Conversely, patients already receiving an optimized dose of avanafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of avanafil and tamsulosin.
    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
    Berotralstat: (Moderate) Use caution if coadministration of berotralstat with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg. The systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 and CYP2D6 substrate and berotralstat is a moderate CYP3A4 and CYP2D6 inhibitor. The effects of concomitant administration of a moderate CYP3A4/CYP2D6 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 inhibition.
    Beta-blockers: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Betaxolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Bisoprolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Bisoprolol; Hydrochlorothiazide, HCTZ: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Boceprevir: (Contraindicated) 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: (Major) Concurrent use of tamsulosin and ceritinib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 like ceritinib are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    Chloramphenicol: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as chloramphenicol. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure; interactions with moderate CYP3A4 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; Codeine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; Dextromethorphan: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; Dextromethorphan; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; Dextromethorphan; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; Dihydrocodeine; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; 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; Ibuprofen; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; Phenylephrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpheniramine; Pseudoephedrine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpheniramine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Chlorpromazine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as chlorpromazine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Cimetidine: (Moderate) 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: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    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: (Moderate) Use caution if coadministration of conivaptan with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A substrate and conivaptan is a moderate CYP3A inhibitor.
    Crizotinib: (Moderate) Use caution if coadministration of crizotinib with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 substrate and crizotinib is a moderate CYP3A4 inhibitor. The effects of concomitant administration of a moderate CYP3A4 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 inhibition.
    Cyclosporine: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as cyclosporine. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure; interactions with moderate CYP3A4 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Dacomitinib: (Moderate) Use caution if coadministration of dacomitinib with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and dacomitinib is a strong CYP2D6 inhibitor. Concomitant treatment with another strong CYP2D6 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively.
    Danazol: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as danazol. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure; interactions with moderate CYP3A4 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Darifenacin: (Moderate) Use caution if coadministration of darifenacin with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP2D6 substrate and darifenacin is a moderate CYP2D6 inhibitor. The effects of concomitant administration of a moderate CYP2D6 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP2D6 inhibition.
    Darunavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Darunavir; Cobicistat: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Darunavir; Cobicistat; Emtricitabine; Tenofovir alafenamide: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    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.
    Desogestrel; 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.
    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; 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: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
    Dronedarone: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of dronedarone. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as dronedarone, should be avoided.
    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.
    Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Alafenamide: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    Elvitegravir; Cobicistat; Emtricitabine; Tenofovir Disoproxil Fumarate: (Major) Concurrent use of tamsulosin and cobicistat is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is metabolized by CYP3A4 and CYP2D6 hepatic enzymes. Cobicistat is a strong inhibitor of CYP3A4 and a CYP2D6 inhibitor. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    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) Use caution when combining tamsulosin with alcohol-containing beverages. Alcohol-containing beverages may increase the effects of tamsulosin, which may lower the blood pressure. Tamsulosin ordinarily does not have much effect on blood pressure and the manufacturer does not make any formal advice on alcohol use, However, published literature suggests that ethanol potentiates antihypertensive effects of alpha blockers, including selective ones like tamsulosin. Some experts advise that the patient to limit alcohol use while using this drug.
    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; 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; 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.
    Ethynodiol Diacetate; 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.
    Etonogestrel; 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.
    Everolimus: (Moderate) Monitor for an increase in tamsulosin-related adverse reactions if coadministration with everolimus is necessary. Tamsulosin is a CYP3A4 and CYP2D6 substrate. Everolimus is a weak CYP3A4 inhibitor and a CYP2D6 inhibitor. The effects of coadministration of both a CYP3A4 and CYP2D6 inhibitor with tamsulosin have not been evaluated; however, there is a potential for significantly increased plasma concentrations of tamsulosin.
    Fedratinib: (Moderate) Use caution if coadministration of fedratinib with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 and CYP2D6 substrate and fedratinib is a moderate CYP3A4 and CYP2D6 inhibitor. The effects of concomitant administration of moderate CYP3A4 and moderate CYP2D6 inhibitors on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 and CYP2D6 inhibition.
    Felodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    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.
    Fluvoxamine: (Moderate) Tamsulosin should be used with caution in combination with moderate inhibitors of CYP3A4 such as fluvoxamine. The cytochrome P450 enzymes CYP3A4 and CYP2D6 are responsible for the extensive metabolism of tamsulosin. Strong inhibitors of CYP3A4 are known to increase the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. No studies have been performed with moderate CYP3A4 inhibitors. As with other alpha adrenergic blocking agents there is a potential risk of syncope with tamsulosin, particularly if serum concentrations are elevated. Monitor blood pressure and observe for symptoms of orthostasis.
    Fosamprenavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Grapefruit juice: (Moderate) Hepatic cytochrome P450 enzymes 2D6 and 3A4 are responsible for the extensive metabolism of tamsulosin. Although no clinical studies have been done, tamsulosin should be used with caution with inhibitors of CYP3A4 isoenzymes (e.g., grapefruit juice).
    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.
    Idelalisib: (Major) Avoid concomitant use of idelalisib, a strong CYP3A inhibitor, with tamsulosin, a CYP3A substrate, as tamsulosin toxicities may be significantly increased. The AUC of a sensitive CYP3A substrate was increased 5.4-fold when coadministered with idelalisib.
    Iloprost: (Minor) Iloprost can have additive effects when administered with other antihypertensive agents, including alpha-blockers. These effects can be used to therapeutic advantage, but dosage adjustments may be necessary.
    Imatinib: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of imatinib, STI-571. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as imatinib, STI-571, should be avoided.
    Indinavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Isavuconazonium: (Moderate) The plasma concentrations of tamsulosin may be elevated when administered concurrently with isavuconazonium. Clinical monitoring for adverse effects, such as hypotension, is recommended during coadministration. Tamsulosin is a substrate of the hepatic isoenzyme CYP3A4 and drug transporter P-glycoprotein (P-gp); isavuconazole, the active moiety of isavuconazonium, is an inhibitor of CYP3A4 and P-gp.
    Isradipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Itraconazole: (Major) Use of tamsulosin is not recommended during and for 2 weeks after itraconazole therapy due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    Ketoconazole: (Major) Avoid use of tamsulosin with strong CYP3A4 inhibitors such as systemic ketoconazole.Tamsulosin is extensively metabolized by CYP3A4 and potent CYP3A4 inhibitors are expected to significantly raise tamsulosin concentrations. Ketoconaozole increased plasma concentrations of tamsulosin; resulting in an increase in the Cmax and AUC of tamsulosin by a 2.2- and 2.8-fold, respectively. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension.
    Labetalol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Lansoprazole; Amoxicillin; Clarithromycin: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of clarithromycin. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as clarithromycin, should be avoided.
    Lefamulin: (Moderate) Use caution if coadministration of oral lefamulin with tamsulosin is necessary, especially at a tamsulosin dose higher than 0.4 mg, as the systemic exposure of tamsulosin may be increased resulting in increased treatment-related adverse reactions including hypotension, dizziness, and vertigo. Tamsulosin is a CYP3A4 substrate and oral lefamulin is a moderate CYP3A4 inhibitor; an interaction is not expected with intravenous lefamulin. The effects of concomitant administration of a moderate CYP3A4 inhibitor on the pharmacokinetics of tamsulosin have not been evaluated, but tamsulosin exposure may increase based on the effects of strong CYP3A4 inhibition.
    Letermovir: (Moderate) An increase in the plasma concentration of tamsulosin may occur when given with letermovir. Avoid this combination in patients who are also receiving treatment with cyclosporine because the magnitude of this interaction may be amplified. Tamsulosin is partially metabolized by CYP3A4. Letermovir is a moderate CYP3A4 inhibitor; however, when given with cyclosporine, the combined effect on CYP3A4 substrates is similar to a strong CYP3A4 inhibitor. In a drug interaction study, concomitant use of tamsulosin with another strong CYP3A4 inhibitor resulted in increase in the maximum plasma concentration and exposure of tamsulosin by a factor of 2.2 and 2.8, respectively. The effects of concurrent use with moderate CYP3A4 inhibitors have not been evaluated.
    Levamlodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    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
    Levonorgestrel; 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.
    Levonorgestrel; Ethinyl Estradiol; Ferrous Bisglycinate: (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.
    Lonafarnib: (Major) Avoid concurrent use of tamsulosin and lonafarnib due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4, and strong inhibitors of CYP3A4, such as lonafarnib, are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    Lopinavir; Ritonavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    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
    Metoprolol; Hydrochlorothiazide, HCTZ: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Mifepristone: (Moderate) Use caution when administering tamsulosin with a moderate CYP3A4 inhibitor such as mifepristone. If concomitant use in necessary, monitor patient closely for increased side effects, including hypotension, since tamsulosin exposure may be increased. Tamsulosin is extensively metabolized by CYP3A4. 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. However, mifepristone is expected to increase concentrations of CYP3A4 substrates. Due to the slow elimination of mifepristone from the body, any interactions that do occur may be prolonged.
    Mirabegron: (Moderate) The effect of mirabegron on tamsulosin pharmacokinetics was determined in drug interaction studies, there was a lack of pharmacokinetic interaction. However, it is recommended that mirabegron be administered with caution in patients taking other medications in the setting of risks for urinary obstruction because of the risk of urinary retention. This includes caution when used with tamsulosin. In addition, mirabegron is a moderate CYP2D6 inhibitor. Exposure of drugs metabolized by CYP2D6 isoenzymes such as tamsulosin may be increased when co-administered with mirabegron.
    Mitotane: (Moderate) Use caution if mitotane and tamsulosin are used concomitantly, and monitor for decreased efficacy of tamsulosin and a possible change in dosage requirements. Mitotane is a strong CYP3A4 inducer and tamsulosin is a CYP3A4 substrate; coadministration may result in decreased plasma concentrations of tamsulosin.
    Nadolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Nebivolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Nebivolol; Valsartan: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Nefazodone: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of nefazodone. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as nefazodone, should be avoided.
    Nelfinavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Nicardipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Nifedipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Nimodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, 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.
    Norethindrone Acetate; Ethinyl Estradiol; 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.
    Norethindrone; 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.
    Norethindrone; Ethinyl Estradiol; 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.
    Norgestimate; 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.
    Olanzapine; 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.
    Olmesartan; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    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: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
    Phentolamine: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
    Pindolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Posaconazole: (Major) Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Plasma concentrations of tamsulosin are increased with concomitant use of ketoconazole, a strong inhibitor of CYP3A4. Concomitant treatment with ketoconazole resulted in an increase in the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use with a strong CYP3A4 inhibitor, such as ketoconazole, itraconazole, posaconazole, or voriconazole should be avoided.
    Prazosin: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
    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.
    Promethazine; Dextromethorphan: (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.
    Promethazine; Phenylephrine: (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
    Propranolol; Hydrochlorothiazide, HCTZ: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Protease inhibitors: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Quinidine: (Moderate) Use caution when administering tamsulosin with a strong CYP2D6 inhibitor such as quinidine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure. If concomitant use in necessary, monitor patient closely for increased side effects.
    Quinine: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of quinine. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as quinine, should be avoided.
    Ranolazine: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of ranolazine. Tamsulosin is extensively metabolized by CYP2D6 and CYP3A4 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Therefore, concomitant use with drugs that inhibit both CYP2D6 and CYP3A4, such as ranolazine, should be avoided.
    Ribociclib: (Major) Concurrent use of tamsulosin and ribociclib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    Ribociclib; Letrozole: (Major) Concurrent use of tamsulosin and ribociclib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    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.
    Segesterone Acetate; 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.
    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: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of sildenafil. Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and tamsulosin.
    Silodosin: (Major) The pharmacodynamic effects of coadministration of silodosin and other alpha-blockers has not been studied. Additive effects on blood pressure or an increased incidence of adverse reactions common to alpha-blocker treatment is possible. Therefore, combined use of silodosin and other alpha-blockers is not recommended.
    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
    Tadalafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest recommended dose of tadalafil. Conversely, patients already receiving an optimized dose of tadalafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. When tadalafil is used for benign prostatic hypertrophy (BPH), discontinue tamsulosin therapy at least 1 day prior to initiating tadalafil therapy. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of tadalafil and tamsulosin.
    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.
    Telmisartan; Amlodipine: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Terazosin: (Major) Tamsulosin should not be administered in combination with other alpha-blockers. The pharmacokinetic and pharmacodynamic interactions between tamsulosin and other alpha-blockers (used for high blood pressure or for benign prostatic hyperplasia) have not been determined. However, interactions or side effects (dizziness, hypotension, syncope, etc.) may be expected from the duplication of pharmacologic effects.
    Terbinafine: (Moderate) Use caution when administering tamsulosin with a moderate CYP2D6 inhibitor such as terbinafine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Thioridazine: (Moderate) Use caution when administering tamsulosin with a CYP2D6 inhibitor such as thioridazine. Tamsulosin is extensively metabolized by CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP2D6 inhibitor resulted in increases in tamsulosin exposure; interactions with moderate CYP2D6 inhibitors have not been evaluated. If concomitant use in necessary, monitor patient closely for increased side effects.
    Timolol: (Minor) Tamsulosin did not potentiate the hypotensive effects of atenolol. However, since the symptoms of orthostasis are reported more frequently in tamsulosin-treated vs. placebo patients, there is a potential risk of enhanced hypotensive effects when co-administered with antihypertensive agents
    Tipranavir: (Major) Plasma concentrations of tamsulosin may be increased with concomitant use of anti-retroviral protease inhibitors. Tamsulosin is extensively metabolized by CYP3A4 and CYP2D6 hepatic enzymes. In clinical evaluation, concomitant treatment with a strong CYP3A4 inhibitor resulted in significant increases in tamsulosin exposure. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension. Therefore, concomitant use of tamsulosin with a strong CYP3A4 inhibitor, or an agent with both CYP3A4 and CYP2D6 inhibitor activity, should be avoided.
    Trandolapril; Verapamil: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Tucatinib: (Major) Concurrent use of tamsulosin and tucatinib is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4, and strong inhibitors of CYP3A4, such as tucatinib, are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    Vardenafil: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on tamsulosin therapy before initiating therapy with the lowest dose of vardenafil. Conversely, patients already receiving an optimized dose of vardenafil should be started on the lowest dose of tamsulosin; increases in the alpha-blocker dose should be done in a stepwise fashion. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of vardenafil and tamsulosin.
    Vemurafenib: (Moderate) Vemurafenib is an inducer of CYP3A4 and decreased plasma concentrations of drugs metabolized by this enzyme, such as tamsulosin, could be expected with concurrent use. Use caution, and monitor therapeutic effects of tamsulosin when coadministered with vemurafenib.
    Verapamil: (Moderate) The concomitant administration of tamsulosin with other antihypertensive agents can cause additive hypotensive effects. In addition, diltiazem, nicardipine, and verapamil may increase tamsulosin plasma concentrations via CYP3A4 inhibition. This interaction can be therapeutically advantageous, but dosages must be adjusted accordingly.
    Voriconazole: (Major) Concurrent use of tamsulosin and voriconazole is not recommended due to the potential for elevated tamsulosin concentrations. Such increases in tamsulosin concentrations may be expected to produce clinically significant and potentially serious side effects, such as hypotension, dizziness, and vertigo. Tamsulosin is extensively metabolized by CYP3A4 hepatic enzymes, and strong inhibitors of CYP3A4 are expected to significantly raise tamsulosin concentrations. Concomitant treatment with another strong CYP3A4 inhibitor increased the Cmax and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively.
    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 only approved by the FDA to treat benign prostatic hyperplasia in men. Tamsulosin is not indicated for use in women and there are no adequate data on the developmental risks associated with the use of tamsulosin during human pregnancy. Animals studies have not revealed adverse developmental effects; however, animal studies are not always predictive of human response.

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

    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.