Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
DUTASTERIDE AND TAMSULOSIN HYDROCHLORIDE vs HYTRIN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Dutasteride inhibits both type 1 and type 2 isoforms of 5α-reductase, preventing conversion of testosterone to dihydrotestosterone (DHT), reducing prostate volume. Tamsulosin is a selective antagonist of alpha-1A and alpha-1D adrenoceptors, relaxing smooth muscle in the prostate and bladder neck.
Selective alpha-1 adrenergic receptor antagonist; inhibits activation of postsynaptic alpha-1 receptors, resulting in relaxation of smooth muscle in the prostate and bladder neck, improving urinary flow and reducing symptoms of benign prostatic hyperplasia (BPH).
treatment of symptomatic benign prostatic hyperplasia (BPH),combination therapy for BPH
Benign prostatic hyperplasia (BPH),Hypertension (as monotherapy or in combination with other antihypertensives)
One capsule (dutasteride 0.5 mg / tamsulosin hydrochloride 0.4 mg) orally once daily, approximately 30 minutes after the same meal each day.
Initial: 1 mg orally once daily at bedtime, increase gradually up to 20 mg/day; typical maintenance: 2-10 mg once daily. For BPH: 5-10 mg once daily. For hypertension: 1-5 mg once daily. Maximum: 20 mg/day.
Dutasteride: Terminal half-life ~5 weeks (3-7 weeks), allowing once-daily dosing; steady-state reached at 3-6 months. Tamsulosin: Terminal half-life ~9-13 hours in healthy subjects, prolonged in elderly (up to 16-19 hours).
Terminal elimination half-life: 12–13 hours (range 10–15 h); clinical context: steady state achieved in 2–3 days; dose adjustment not required in renal impairment but caution in hepatic impairment.
Dutasteride is extensively metabolized by CYP3A4 and CYP3A5; tamsulosin is primarily metabolized by CYP2D6 and to a lesser extent by CYP3A4.
Extensively metabolized in the liver via demethylation and dehydrogenation; multiple metabolites are formed, some pharmacologically active. CYP450 enzymes involved include CYP3A4 and CYP2D6.
Dutasteride: 40% as metabolites in feces (mainly via bile), 5% in urine. Tamsulosin: 76% in urine as unchanged drug and metabolites, 24% in feces.
Renal: ~40% as metabolites, <1% unchanged; biliary/fecal: ~60% as metabolites; total clearance 6.4 L/h.
Dutasteride: >99.5% bound to albumin and alpha-1-acid glycoprotein. Tamsulosin: 94-99% bound to alpha-1-acid glycoprotein.
90–94% bound to albumin; free fraction 6–10%.
Dutasteride: Vd 300-500 L (total body, large tissue distribution). Tamsulosin: Vd 0.2 L/kg (approx 14-30 L, moderate distribution).
Vd: 3.9 L/kg (range 3.5–4.3 L/kg); large Vd indicates extensive tissue distribution, high affinity for vascular smooth muscle.
Dutasteride: Oral bioavailability ~60% (enhanced with food). Tamsulosin: Oral bioavailability ~30% (increased with food; formulation designed for consistent absorption).
Oral bioavailability: >90% (first-pass metabolism minimal); food does not affect absorption.
No dosage adjustment is required for renal impairment. Tamsulosin is extensively metabolized and renally excreted as inactive metabolites; however, no specific GFR-based adjustments are recommended.
No specific GFR-based dose adjustment required; use with caution in severe renal impairment (Cr Cl <30 m L/min) due to potential accumulation.
Dutasteride is contraindicated in patients with severe hepatic impairment (Child-Pugh Class C). For mild to moderate hepatic impairment (Child-Pugh A or B), no dosage adjustment is recommended, but caution is advised.
Contraindicated in severe hepatic impairment (Child-Pugh class C). For mild to moderate (Child-Pugh A or B), initial dose 1 mg at bedtime, titrate cautiously; monitor for hypotension.
Safety and efficacy in pediatric patients have not been established. Use is not recommended in patients under 18 years of age.
Not approved for use in children; safety and efficacy not established.
No specific dose adjustment is required based on age alone. Elderly patients may be more sensitive to orthostatic hypotension from tamsulosin; monitor blood pressure and advise caution when rising from a seated or lying position.
Initiate at 1 mg at bedtime to minimize orthostatic hypotension; titrate slowly. Elderly patients may experience increased sensitivity to hypotensive effects. Monitor blood pressure and renal function.
None
None.
Orthostatic hypotension/syncope, especially with concurrent antihypertensives,Intraoperative floppy iris syndrome during cataract surgery,Risk of high-grade prostate cancer (increased Gleason score 8-10 with dutasteride),Hepatic impairment may increase exposure,Sexual dysfunction: decreased libido, erectile dysfunction, ejaculation disorders
Orthostatic hypotension and syncope, especially with first dose (first-dose effect); dose titration recommended.,Priapism (rare); advise patient to seek immediate medical attention if erection persists >4 hours.,Intraoperative floppy iris syndrome (IFIS) during cataract surgery in patients on alpha-1 blockers.,Use with caution in patients with renal impairment or hepatic impairment.,May cause dizziness, drowsiness, or blurred vision; caution when driving or operating machinery.
Hypersensitivity to dutasteride, tamsulosin, or other 5α-reductase inhibitors,Women who are or may become pregnant (risk of fetal harm due to androgen inhibition),Severe hepatic impairment (Child-Pugh Class C),History of orthostatic hypotension
Hypersensitivity to terazosin or any component of the formulation.,Concomitant use with phosphodiesterase-5 inhibitors (e.g., sildenafil) may increase risk of hypotension (relative contraindication; use with caution).
Absorption of tamsulosin is decreased when taken with food; however, the combination product should be taken 30 minutes after a meal to maintain consistent exposure. Avoid grapefruit juice as it may increase tamsulosin concentrations. No specific food interactions with dutasteride.
No significant food interactions. Avoid grapefruit juice as it may increase drug levels. Take with or without food. Limit alcohol intake as it may enhance orthostatic effects.
Dutasteride is contraindicated in pregnancy due to risk of fetal harm, particularly male genital abnormalities (e.g., hypospadias) from inhibition of dihydrotestosterone. Tamsulosin has no known teratogenic risk. First trimester: Dutasteride exposure may cause feminization of male fetuses. Second and third trimesters: Risk persists; avoid use.
Terazosin (HYTRIN) is FDA Pregnancy Category C. No adequate and well-controlled studies in pregnant women. In animal studies, terazosin was not teratogenic in rats or rabbits at doses up to 200 mg/kg/day (rat) and 75 mg/kg/day (rabbit), but delayed fetal ossification was observed. Risk cannot be ruled out; use only if potential benefit justifies potential risk to fetus.
Unknown if dutasteride or tamsulosin are excreted in human milk. Dutasteride is lipophilic and may appear in milk. Tamsulosin likely excreted. M/P ratio not available. Due to potential for adverse effects (e.g., hypotension), breastfeeding is not recommended during therapy.
It is not known whether terazosin is excreted in human milk. The M/P ratio is unknown. Caution is advised when administered to a nursing woman; consider developmental and health benefits of breastfeeding along with mother's clinical need.
No dose adjustment studies in pregnancy. Dutasteride should not be used; tamsulosin is not recommended. No pharmacokinetic changes requiring dose adjustment are established, but avoid use.
No specific pharmacokinetic data in pregnancy. However, pregnancy may alter volume of distribution and hepatic clearance, potentially affecting drug levels. Dose adjustments may be needed based on clinical response and blood pressure monitoring. Start with lowest effective dose and titrate cautiously.
Dutasteride/tamsulosin is a fixed-dose combination for benign prostatic hyperplasia (BPH). Dutasteride is a 5α-reductase inhibitor that reduces prostate volume over months; tamsulosin is an α1-adrenoceptor antagonist providing rapid symptom relief. Do not split or crush capsules. Avoid use in women and children. Monitor for orthostatic hypotension, especially when initiating therapy. Assess for drug-drug interactions: CYP3A4 inhibitors (e.g., ketoconazole) increase dutasteride exposure; tamsulosin interacts with other α-blockers, antihypertensives, and PDE5 inhibitors. Counsel patients about risk of postural hypotension and syncope. Advise patients to avoid driving or hazardous activities until they know how the medication affects them. Dutasteride may cause sexual dysfunction (decreased libido, ejaculatory dysfunction, gynecomastia). Tamsulosin may cause intraoperative floppy iris syndrome during cataract surgery; inform ophthalmologist of use. Monitor serum PSA levels: dutasteride decreases PSA by ~50% after 6 months; establish new baseline. Do not use in patients with history of prostate cancer.
HYTRIN (terazosin) is an alpha-1 adrenergic blocker used for hypertension and benign prostatic hyperplasia (BPH). First-dose syncope can occur; start with 1 mg at bedtime. Titrate slowly to avoid orthostatic hypotension. Monitor blood pressure 2-3 hours after initial dose and after dose increases. May cause intraoperative floppy iris syndrome (IFIS) in cataract surgery; notify ophthalmologist. Use with caution in patients with renal impairment. Can be used alone or with other antihypertensives.
Take this medication once daily, 30 minutes after the same meal each day.,Swallow capsules whole; do not crush, chew, or open.,Rise slowly from sitting or lying down to avoid dizziness or fainting.,Avoid driving or operating machinery until you know how the drug affects you.,Inform your doctor if you plan to have cataract surgery, as this drug may cause complications.,Do not donate blood while taking this medication, as it may harm a fetus if given to a pregnant woman.,Women who are pregnant or may become pregnant should not handle crushed or broken capsules.,Report any breast lumps, pain, or nipple discharge, as gynecomastia is possible.,Use condoms if your partner is pregnant, as dutasteride can be absorbed through skin contact with semen.,Keep all appointments for PSA blood tests; the test result will be lower than expected.,Do not take other alpha-blocker medications for blood pressure or prostate problems while on this drug unless prescribed.,Grapefruit juice may increase side effects; limit or avoid consumption.,Do not stop taking this medication suddenly without consulting your doctor.
Take the first dose at bedtime to minimize dizziness or fainting.,Avoid sudden standing or sitting up quickly to prevent orthostatic hypotension.,Report any prolonged erections lasting more than 4 hours immediately.,Avoid driving or hazardous activities until you know how the drug affects you.,Do not stop taking abruptly; consult doctor for gradual dose reduction.,Inform all healthcare providers, especially eye surgeons, that you are taking terazosin.
"Tamsulosin, an alpha-1 adrenergic antagonist, and fosinopril, an ACE inhibitor, both lower blood pressure through distinct mechanisms, leading to additive hypotensive effects. This synergistic action increases the risk of orthostatic hypotension, dizziness, syncope, and falls, particularly at treatment initiation or dose escalation. The interaction is of clinical concern in elderly patients or those with volume depletion."
"Lofexidine, a central alpha-2 adrenergic agonist, reduces sympathetic outflow and can cause bradycardia and hypotension. Tamsulosin, an alpha-1 adrenergic receptor antagonist, also lowers blood pressure, especially orthostatic. Combined use leads to additive hypotensive effects, increasing risk of symptomatic bradycardia, orthostatic hypotension, syncope, and falls, particularly at therapy initiation or dose titration."
"The combination of tamsulosin and moexipril can lead to an increased risk of hypotension and orthostatic hypotension due to additive vasodilatory effects. Tamsulosin, an alpha-1 adrenergic antagonist, reduces peripheral vascular resistance, while moexipril, an ACE inhibitor, decreases angiotensin II production, further promoting vasodilation. This synergistic effect may cause symptomatic hypotension, dizziness, and syncope, particularly at the initiation of therapy or during dose adjustments."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about DUTASTERIDE AND TAMSULOSIN HYDROCHLORIDE vs HYTRIN, answered by our medical review team.
DUTASTERIDE AND TAMSULOSIN HYDROCHLORIDE is a Alpha-1 Blocker that works by Dutasteride inhibits both type 1 and type 2 isoforms of 5α-reductase, preventing conversion of testosterone to dihydrotestosterone (DHT), reducing prostate volume. Tamsulosin is a selective antagonist of alpha-1A and alpha-1D adrenoceptors, relaxing smooth muscle in the prostate and bladder neck.. HYTRIN is a Alpha-1 Blocker that works by Selective alpha-1 adrenergic receptor antagonist; inhibits activation of postsynaptic alpha-1 receptors, resulting in relaxation of smooth muscle in the prostate and bladder neck, improving urinary flow and reducing symptoms of benign prostatic hyperplasia (BPH).. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between DUTASTERIDE AND TAMSULOSIN HYDROCHLORIDE and HYTRIN depend on the specific clinical indication. These are both Alpha-1 Blocker agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of DUTASTERIDE AND TAMSULOSIN HYDROCHLORIDE is: One capsule (dutasteride 0.5 mg / tamsulosin hydrochloride 0.4 mg) orally once daily, approximately 30 minutes after the same meal each day.. The standard adult dose of HYTRIN is: Initial: 1 mg orally once daily at bedtime, increase gradually up to 20 mg/day; typical maintenance: 2-10 mg once daily. For BPH: 5-10 mg once daily. For hypertension: 1-5 mg once daily. Maximum: 20 mg/day.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between DUTASTERIDE AND TAMSULOSIN HYDROCHLORIDE and HYTRIN in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. DUTASTERIDE AND TAMSULOSIN HYDROCHLORIDE is classified as Category A/B. Dutasteride is contraindicated in pregnancy due to risk of fetal harm, particularly male genital abnormalities (e.g., hypospadias) from inhibition of dihydrotestosterone. Tamsulosi. HYTRIN is classified as Category C. Terazosin (HYTRIN) is FDA Pregnancy Category C. No adequate and well-controlled studies in pregnant women. In animal studies, terazosin was not teratogenic in rats or rabbits at do. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.