Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PROSCAR vs DUTASTERIDE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Finasteride inhibits 5α-reductase type II, preventing conversion of testosterone to dihydrotestosterone (DHT) in the prostate, reducing prostate volume and improving urinary symptoms.
Competitive inhibitor of type II and type I 5α-reductase isoenzymes, blocking conversion of testosterone to dihydrotestosterone (DHT) in prostate, hair follicles, and other tissues.
Benign prostatic hyperplasia (BPH) to improve symptoms, reduce risk of acute urinary retention, and reduce need for surgery,Androgenetic alopecia (male pattern hair loss) - off-label for some formulations
FDA: Treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate,FDA: Reduce risk of acute urinary retention,FDA: Reduce need for BPH-related surgery,Off-label: Male androgenetic alopecia
5 mg orally once daily.
0.5 mg orally once daily.
Terminal elimination half-life is 6-8 hours (range 4-12 hours) in young adults; prolonged to 8-10 hours in elderly (≥70 years), but no dose adjustment required. Steady-state reached after 2 weeks dosing.
Terminal half-life approximately 3-4 weeks (21-35 days) in young adults; 5-6 weeks in elderly; supports once-daily dosing due to slow elimination.
Primarily metabolized by CYP3A4 to t-butyl side-chain hydroxylated metabolites; minor metabolism by other CYP enzymes.
Extensively metabolized in liver via CYP3A4 and CYP1A2; minor metabolism by CYP2C8, CYP2C9, CYP2C19, and CYP2D6.
Primarily hepatic metabolism (CYP3A4), metabolites excreted renally (39%) and fecally (57%) as unchanged drug and metabolites.
Primarily fecal (70%) as metabolites; renal excretion accounts for <5% unchanged drug.
Approximately 90% bound to plasma proteins (albumin and alpha-1-acid glycoprotein).
>99% bound to albumin and alpha-1 acid glycoprotein; high affinity.
Apparent volume of distribution is 1.4 L/kg (range 0.8-2.0 L/kg), indicating extensive tissue distribution (including prostate, seminal vesicles, and skin).
Approximately 300-500 L (3-5 L/kg), indicating extensive tissue distribution, particularly to prostate and seminal vesicles.
Oral bioavailability is approximately 63-80% (mean 65% from tablet formulation); food does not significantly affect absorption (Cmax decreased by 8%, AUC unchanged).
Oral: Approximately 60% (range 40-80%) with food; not administered parenterally.
No adjustment required for renal impairment; dose adjustment not studied in GFR < 30 m L/min.
No dose adjustment required for renal impairment (including dialysis).
No specific guidelines for Child-Pugh A or B; use with caution in severe hepatic impairment.
Contraindicated in Child-Pugh Class C; use with caution in mild to moderate impairment (Child-Pugh A/B) with no specific dose adjustment established.
Not indicated for use in pediatric patients; safety and efficacy not established.
Not indicated in pediatric patients; safety and efficacy not established.
No specific dose adjustment required; normal adult dosing recommended.
No specific dose adjustment required; monitor for adverse effects (e.g., dizziness, orthostatic hypotension) due to age-related comorbidities.
Not approved for use in women or children; finasteride is contraindicated in women who are or may become pregnant due to risk of hypospadias in male fetuses.
No FDA black box warning.
Increased risk of high-grade prostate cancer (Gleason score 8-10) reported in clinical trials; monitor for urinary obstruction; evaluate for other urological diseases; potential for decreased serum PSA levels; sexual dysfunction (decreased libido, erectile dysfunction, ejaculation disorder) may persist after discontinuation; mood changes including depression; breast cancer risk not established.
Risk of high-grade prostate cancer in men aged 50-79 with elevated PSA and previous negative biopsy (see PLCO trial),Increased risk of sexual adverse events (impotence, decreased libido, ejaculation disorders) that may persist after discontinuation,Elevated PSA levels: use caution when interpreting PSA values; establish new baseline after 6 months of treatment
Hypersensitivity to finasteride or any component, women who are or may become pregnant, pediatric patients (not indicated).
Women of childbearing potential (pregnancy category X; risk of fetal harm due to inhibition of 5α-reductase),History of hypersensitivity to dutasteride or other 5α-reductase inhibitors,Pediatric patients
No significant food interactions. Can be taken with or without meals.
No clinically significant food interactions. May be taken with or without food. Grapefruit juice does not affect dutasteride levels to a clinically relevant extent.
Finasteride is contraindicated in pregnancy (Category X). In first trimester, exposure may cause hypospadias in male fetuses due to inhibition of 5α-reductase; second and third trimester risks include ambiguous genitalia in male fetuses. Avoid handling crushed tablets if pregnant.
Dutasteride is contraindicated in pregnancy. It is a 5α-reductase inhibitor that can inhibit the conversion of testosterone to dihydrotestosterone (DHT), potentially causing abnormal development of external genitalia in male fetuses. Risk extends throughout all trimesters due to potential disruption of androgen-mediated development in male fetuses during the first trimester and cumulative effects from drug accumulation in adipose tissue. No adequate human studies exist; animal studies show teratogenicity in male offspring at clinically relevant doses.
Finasteride is excreted in breast milk in very low amounts (M/P ratio 0.52). Limited data; use caution. Consider alternative therapy, especially in nursing mothers of male infants due to theoretical risk of antiandrogenic effects.
No data on dutasteride in human milk. M/P ratio unknown. Dutasteride is highly lipophilic and likely excreted in breast milk. Because of potential adverse effects on the nursing infant (e.g., interference with androgen-mediated development in male infants), breastfeeding is contraindicated during therapy and for at least 6 months after the last dose due to long half-life (approximately 5 weeks).
Not applicable; use is contraindicated in pregnancy. No pharmacokinetic studies in pregnancy; no dose adjustments recommended for any trimester as use is not indicated.
No dose adjustment studies in pregnancy because dutasteride is contraindicated. Pharmacokinetic changes in pregnancy (increased volume of distribution, altered metabolism) could affect dutasteride levels, but no adjustments are recommended as drug should not be used. If inadvertently used, discontinue immediately and monitor for adverse effects.
Proscar (finasteride 5 mg) is indicated for benign prostatic hyperplasia (BPH); not interchangeable with Propecia (1 mg) for alopecia. Onset of symptom improvement may take 6-12 months. Monitor serum PSA (multiply by 2 for first 2 years). May cause reversible decrease in libido, ejaculatory dysfunction. Avoid in women of childbearing potential due to teratogenicity (risk of hypospadias).
Monitor PSA levels cautiously, as dutasteride reduces serum PSA by approximately 50% after 6 months; double the PSA value for comparison to untreated men. Do not handle crushed or broken capsules if pregnant or planning pregnancy, as absorption through skin may cause fetal harm. Assess for signs of high-grade prostate cancer before initiating therapy, as dutasteride may increase the risk of Gleason 8-10 tumors. Onset of symptom relief may take 3-6 months; do not discontinue prematurely. Avoid concomitant use with strong CYP3A4 inhibitors (e.g., ritonavir, ketoconazole) as they increase dutasteride exposure.
Take once daily with or without food.,Do not crush or split tablets.,Symptom improvement may take 6 months or longer.,Possible side effects include decreased libido, erectile dysfunction, or decreased semen volume.,Women who are pregnant or may become pregnant should not handle crushed or broken tablets.,Regular monitoring of PSA levels is required during treatment.,Do not donate blood while taking this medication.,Report any breast lumps or testicular pain to your healthcare provider.
Take exactly as prescribed; do not stop or change dose without consulting your doctor.,Swallow the capsule whole; do not chew or open it.,It may take 3 to 6 months to see improvement in symptoms.,Avoid handling leaking or crushed capsules if you are a woman who is or may become pregnant; wash area immediately with soap and water if skin contact occurs.,Do not donate blood for at least 6 months after your last dose to prevent exposure to a pregnant woman.,Report any breast lumps, pain, or nipple discharge promptly.,You will need regular blood tests for PSA level monitoring; inform your doctor that you are taking dutasteride.,Dutasteride can decrease sperm count and may affect fertility; discuss this with your doctor if planning to father a child.
No interactions on record
"Dutasteride, a 5α-reductase inhibitor, may inhibit cytochrome P450 enzymes, particularly CYP3A4, which is involved in the metabolism of sulfisoxazole. This inhibition can lead to decreased clearance of sulfisoxazole, resulting in elevated plasma concentrations. Increased sulfisoxazole levels may potentiate its adverse effects, including hypersensitivity reactions, crystalluria, and hematologic toxicity such as agranulocytosis."
"Concomitant use of dutasteride, a 5α-reductase inhibitor, with nelfinavir, a protease inhibitor and potent CYP3A4 inhibitor, is predicted to increase the serum concentration of nelfinavir. This occurs because dutasteride may inhibit the metabolism of nelfinavir via competition for CYP3A4, leading to elevated nelfinavir levels and an increased risk of adverse effects such as gastrointestinal disturbances, hepatotoxicity, and metabolic complications. Clinical monitoring for toxicity and dose adjustments are warranted."
"Dutasteride, a 5α-reductase inhibitor, is metabolized primarily by CYP3A4 and to a lesser extent by CYP2D6. Itraconazole is a potent inhibitor of CYP3A4 and also inhibits P-glycoprotein. Coadministration leads to significantly increased serum concentrations of dutasteride, raising the risk of adverse effects such as gynecomastia, sexual dysfunction, and depression. The effect on itraconazole levels is minimal and clinically irrelevant."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PROSCAR vs DUTASTERIDE, answered by our medical review team.
PROSCAR is a 5-Alpha Reductase Inhibitor that works by Finasteride inhibits 5α-reductase type II, preventing conversion of testosterone to dihydrotestosterone (DHT) in the prostate, reducing prostate volume and improving urinary symptoms.. DUTASTERIDE is a 5-alpha Reductase Inhibitor that works by Competitive inhibitor of type II and type I 5α-reductase isoenzymes, blocking conversion of testosterone to dihydrotestosterone (DHT) in prostate, hair follicles, and other tissues.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PROSCAR and DUTASTERIDE depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of PROSCAR is: 5 mg orally once daily.. The standard adult dose of DUTASTERIDE is: 0.5 mg orally once daily.. 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 PROSCAR and DUTASTERIDE 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. PROSCAR is classified as Category C. Finasteride is contraindicated in pregnancy (Category X). In first trimester, exposure may cause hypospadias in male fetuses due to inhibition of 5α-reductase; second and third tri. DUTASTERIDE is classified as Category D/X. Dutasteride is contraindicated in pregnancy. It is a 5α-reductase inhibitor that can inhibit the conversion of testosterone to dihydrotestosterone (DHT), potentially causing abnorm. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.