Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PROPECIA vs PROSCAR
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Finasteride is a competitive and specific inhibitor of type II 5α-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT). By inhibiting 5α-reductase, finasteride reduces serum and intraprostatic DHT levels, decreasing androgenic stimulation of the prostate. In hair follicles, reduction of DHT levels slows hair loss and promotes hair regrowth.
Finasteride inhibits 5α-reductase type II, preventing conversion of testosterone to dihydrotestosterone (DHT) in the prostate, reducing prostate volume and improving urinary symptoms.
Treatment of male pattern hair loss (androgenetic alopecia) in men only,Treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate
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
1 mg orally once daily
5 mg orally once daily.
Terminal elimination half-life is approximately 6-8 hours in young adults (range 4-12 hours), with clinical relevance for once-daily dosing; slightly prolonged in elderly (8-11 hours).
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.
Finasteride is extensively metabolized in the liver, primarily via the cytochrome P450 3A4 enzyme system. Two major metabolites, t-butyl side chain hydroxylation and ω-hydroxylation, have been identified; these metabolites possess less than 20% of the 5α-reductase inhibitory activity of finasteride.
Primarily metabolized by CYP3A4 to t-butyl side-chain hydroxylated metabolites; minor metabolism by other CYP enzymes.
Primarily hepatic metabolism; 57% excreted in feces (as metabolites), 39% in urine (as metabolites, <0.1% as unchanged finasteride).
Primarily hepatic metabolism (CYP3A4), metabolites excreted renally (39%) and fecally (57%) as unchanged drug and metabolites.
Approximately 93% bound to plasma proteins (mainly albumin).
Approximately 90% bound to plasma proteins (albumin and alpha-1-acid glycoprotein).
Approximately 1.1 L/kg (range 0.9-1.3 L/kg), indicating extensive tissue distribution with penetration into seminal fluid and scalp tissue.
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).
Oral bioavailability is approximately 65% (range 60-70%); not affected by food.
Oral bioavailability is approximately 63-80% (mean 65% from tablet formulation); food does not significantly affect absorption (Cmax decreased by 8%, AUC unchanged).
No dose adjustment required for any degree of renal impairment
No adjustment required for renal impairment; dose adjustment not studied in GFR < 30 m L/min.
No dose adjustment recommended; no studies in hepatic impairment
No specific guidelines for Child-Pugh A or B; use with caution in severe hepatic impairment.
Not indicated in pediatric patients; safety and efficacy not established
Not indicated for use in pediatric patients; safety and efficacy not established.
No specific dose adjustment; limited data in elderly men with benign prostatic hyperplasia
No specific dose adjustment required; normal adult dosing recommended.
PROPECIA is not approved for use in women or children. Finasteride is contraindicated in women who are or may become pregnant due to risk of abnormalities of the external genitalia of a male fetus. Women should not handle crushed or broken tablets when pregnant or may be pregnant.
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.
Risk of prostate cancer: Finasteride may increase the risk of high-grade prostate cancer; digital rectal exam and PSA screening recommended before and during therapy.,Sexual dysfunction: Decreased libido, erectile dysfunction, ejaculation disorders, and decreased ejaculate volume have been reported; may persist after discontinuation.,Depression and suicidal ideation: Monitor for mood changes.,Breast cancer: Reported in men; evaluate any breast changes promptly.,Elevated PSA levels: Use caution interpreting PSA values in men on finasteride; adjust PSA levels by approximately 50% for clinical interpretation.,Hepatic impairment: Use with caution in patients with liver function abnormalities.,Pediatric use: Not indicated for use in children.
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.
Hypersensitivity to finasteride or any component of the formulation,Women who are or may become pregnant (due to risk of hypospadias in male fetuses),Children (not indicated for use in pediatric patients)
Hypersensitivity to finasteride or any component, women who are or may become pregnant, pediatric patients (not indicated).
No clinically significant food interactions. May be taken with or without food. However, avoid excessive alcohol intake as it may exacerbate certain side effects (e.g., dizziness).
No significant food interactions. Can be taken with or without meals.
Contraindicated in females of childbearing potential. Finasteride inhibits conversion of testosterone to DHT, and risk of hypospadias in male fetuses if exposure occurs during gestation. No adequate studies in pregnant women; animal studies show abnormal external genitalia in male offspring at doses 1-100 times human exposure.
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.
Not recommended. M/P ratio unknown. Finasteride is excreted in rat milk; no human data.
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 dose adjustments applicable as drug is contraindicated in pregnancy.
Not applicable; use is contraindicated in pregnancy. No pharmacokinetic studies in pregnancy; no dose adjustments recommended for any trimester as use is not indicated.
Monitor patients for sexual dysfunction (e.g., decreased libido, erectile dysfunction) which may persist after discontinuation. Finasteride lowers serum PSA by approximately 50%; when interpreting PSA values in men taking Propecia, double the measured value for prostate cancer screening. Use with caution in patients with liver impairment; hepatic metabolism is primary clearance route. Avoid handling crushed or broken tablets in women who are or may become pregnant due to risk of teratogenicity (fetal genital abnormalities). Onset of hair regrowth typically takes 3-6 months; continue use for at least 12 months before assessing efficacy.
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).
Take exactly as prescribed, usually one tablet (1 mg) daily with or without food.,Do not stop or skip doses without consulting your doctor; continuous use is needed to maintain benefit.,It may take 3-6 months to see hair regrowth and up to 12 months for full effect.,Report any new or worsening sexual side effects (e.g., decreased libido, erectile dysfunction, ejaculation disorders) promptly.,Finasteride may increase the risk of high-grade prostate cancer; discuss screening risks with your doctor.,Do not donate blood while taking Propecia and for at least 1 month after stopping to prevent exposure to pregnant women.,Women who are pregnant or may become pregnant should not handle crushed or broken tablets due to risk of birth defects.,If a dose is missed, skip it and take the next dose at the usual time; do not double up.
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.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PROPECIA vs PROSCAR, answered by our medical review team.
PROPECIA is a 5-alpha reductase inhibitor that works by Finasteride is a competitive and specific inhibitor of type II 5α-reductase, an intracellular enzyme that converts testosterone to dihydrotestosterone (DHT). By inhibiting 5α-reductase, finasteride reduces serum and intraprostatic DHT levels, decreasing androgenic stimulation of the prostate. In hair follicles, reduction of DHT levels slows hair loss and promotes hair regrowth.. 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.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PROPECIA and PROSCAR 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 PROPECIA is: 1 mg orally once daily. The standard adult dose of PROSCAR is: 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 PROPECIA and PROSCAR 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. PROPECIA is classified as Category C. Contraindicated in females of childbearing potential. Finasteride inhibits conversion of testosterone to DHT, and risk of hypospadias in male fetuses if exposure occurs during gest. 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. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.