What are the uses of finasteride (Propecia)?

Finasteride Uses

Finasteride is FDA-approved for two primary indications: treatment of symptomatic benign prostatic hyperplasia (BPH) in men with enlarged prostates at 5 mg daily, and treatment of male pattern hair loss (androgenetic alopecia) in men at 1 mg daily. 1

Benign Prostatic Hyperplasia (BPH)

Mechanism and Efficacy

• Finasteride inhibits type 2 5α-reductase enzyme, blocking conversion of testosterone to dihydrotestosterone (DHT), resulting in approximately 20-25% reduction in prostate volume 2, 3
• Finasteride reduces prostate size, increases peak urinary flow rate, and reduces BPH symptoms, with the average patient experiencing a 3-point improvement in the AUA Symptom Index 2
• The drug reduces risk of acute urinary retention and need for BPH-related surgery, with absolute benefit increasing with rising prostate volume or serum PSA 2

Critical Patient Selection Criteria

• Finasteride is NOT appropriate for men with lower urinary tract symptoms (LUTS) who do not have prostatic enlargement—it is ineffective in this population 2, 3
• Greatest benefit occurs in men with larger glands (>40 grams) or higher PSA values, as these patients face higher risk of disease progression 2
• Symptom improvement requires long-term therapy; benefits are lost when treatment is withdrawn 4

Dosing and Monitoring

• Standard dose: 5 mg once daily for BPH 1, 5
• PSA levels must be doubled after 12 months of finasteride therapy to accurately interpret prostate cancer screening results, as finasteride reduces PSA by approximately 50% 3, 1

Male Pattern Hair Loss (Androgenetic Alopecia)

Efficacy Profile

• Finasteride 1 mg daily produces visible hair growth in up to 66% of men with mild to moderate alopecia and stops hair loss in 91% of patients 6, 7
• Visible improvement typically begins by 12 weeks, with maximal benefit at 1-2 years 3, 8
• In men with vertex hair loss, global photographs showed improvement in 48% at 1 year and 66% at 2 years, compared with 7% of placebo recipients 7
• Hair counts demonstrated that 83% of finasteride recipients versus 28% of placebo recipients had no further hair loss at 2 years 7

Patient Selection

• Treatment should be initiated in men aged 18-60 years seeking medical treatment for androgenetic alopecia 3
• The proven preservative effect of finasteride provides strong indication for prescribing it in early cases before much hair has been lost 6
• Hair loss resumes following withdrawal of finasteride, confirming the need for continuous therapy 6

Dosing

• Standard dose: 1 mg once daily for androgenetic alopecia 1, 9, 7

Prostate Cancer Chemoprevention (Investigational/Controversial)

Evidence Base

• The Prostate Cancer Prevention Trial (PCPT) demonstrated a decrease in cumulative incidence of prostate cancer from 24.4% in placebo to 18.4% in finasteride arm over 7 years 2
• However, an observed increase in Gleason scores 7-10 tumors in the finasteride arm (37%) compared with placebo (22.2%) triggered significant concern about potential harm 2, 1

Current Guideline Recommendations

• Asymptomatic men with PSA ≤3.0 ng/mL who are regularly screened with PSA may benefit from discussion of 5-ARIs for 7 years for prevention, but must be counseled about the potential risk of high-grade prostate cancer 2
• Men already taking 5-ARIs for benign conditions (BPH or hair loss) should receive similar counseling about prostate cancer prevention benefits and risks 2
• This is NOT a routine recommendation—it requires individualized shared decision-making based on patient risk factors and values 2

Adverse Effects Profile

Sexual Dysfunction

• Reported adverse events are primarily sexually related: decreased libido, ejaculatory dysfunction, and erectile dysfunction 2
• Sexual adverse events occur in 3.8% of finasteride recipients versus 2.1% of placebo recipients 7
• These effects are typically reversible after discontinuation and uncommon after the first year of therapy 2
• Postmarketing reports describe sexual dysfunction that continued after discontinuation in rare cases, though causality is uncertain 1

Other Adverse Effects

• Gynecomastia: 4.5% with finasteride versus 2.8% with placebo in long-term studies 2
• Decreased ejaculate volume 2, 9
• Rare reports of male breast cancer (relationship to finasteride currently unknown) 1
• Rare reports of male infertility and/or poor seminal quality (normalization reported after discontinuation) 1

Contraindications

• Finasteride is absolutely contraindicated in pregnant women due to risk of hypospadias in male fetuses 7
• Women should not handle crushed or broken tablets 1

Common Pitfalls and Clinical Caveats

• Do not prescribe finasteride for LUTS in men without documented prostatic enlargement—it will be ineffective 2, 3
• Remember to adjust PSA interpretation by doubling the value after 12 months of therapy 3
• Counsel patients that benefits require continuous therapy and are lost upon discontinuation 4, 6
• For hair loss, set realistic expectations: treatment prevents further loss more reliably than it regrows hair 6, 7
• Sexual side effects peak in the first year and often resolve with continued therapy 2
• Patients with higher baseline PSA or larger prostates derive greater benefit for BPH but also face higher baseline risk 2