What is the recommended dose of finasteride (Finasteride) for benign prostatic hyperplasia (BPH) and androgenetic alopecia?

Finasteride Dosing for BPH and Androgenetic Alopecia

For benign prostatic hyperplasia (BPH), use finasteride 5 mg once daily; for androgenetic alopecia (male pattern hair loss), use finasteride 1 mg once daily. 1, 2

Dosing by Indication

BPH Treatment

• Finasteride 5 mg daily is the established dose for BPH, consistently used across all major clinical trials including PCPT, MTOPS, PLESS, PREDICT, and VA Cooperative studies 1
• The FDA-approved dose of 5 mg/day was evaluated in multiple placebo-controlled studies showing significant efficacy in men with moderate to severe BPH symptoms 2
• Critical patient selection criterion: Finasteride is only effective in men with documented prostatic enlargement (prostate volume >30cc on imaging) 1, 3
• Do not use finasteride in men with lower urinary tract symptoms who lack prostatic enlargement, as it is ineffective in this population 1, 3

Androgenetic Alopecia Treatment

• Finasteride 1 mg once daily is the recommended dose for male pattern hair loss in men aged 18-60 years 1
• Visible improvement typically begins by 12 weeks, with maximal benefit at 1-2 years 1
• The 1 mg dose produces similar DHT suppression (approximately 50% PSA reduction after 12 months) as the 5 mg dose used for BPH 1, 4

Critical PSA Monitoring Requirement

All men taking finasteride at either dose (1 mg or 5 mg) must have their PSA values doubled after 12 months of therapy when screening for prostate cancer 1, 3

• Finasteride reduces serum PSA by approximately 50% after one year at both the 1 mg and 5 mg doses 1, 4
• Men aged 40-49 years on 1 mg finasteride show a median 40% decrease in PSA; men aged 50-60 years show a median 50% decrease 4
• Failure to adjust PSA interpretation is a common and dangerous pitfall that can delay prostate cancer detection 3

Duration and Efficacy Expectations

BPH

• Counsel patients that symptom improvement takes several months—finasteride has a slower onset than alpha-blockers 3
• Patients experience an average 3-point improvement in AUA Symptom Index, which is clinically meaningful 3, 2
• Long-term studies demonstrate sustained symptom improvements of 3-4 points maintained for 6-10 years 1, 3
• Finasteride reduces prostate size by 15-25% within 6 months through 70% reduction in prostatic DHT 3

Androgenetic Alopecia

• Efficacy is maintained over 5+ years of continuous treatment 1
• Hair loss resumes if treatment is discontinued, so patients must understand this is lifelong therapy 1

Common Side Effects

The most frequently reported adverse reactions relate to sexual function 2:

• Decreased libido: 6.4% in year 1, declining to 2.6% in years 2-4 3
• Ejaculatory dysfunction: 3.7% in year 1, declining to 1.5% in years 2-4 3
• Impotence: 8.1% in year 1 (vs 3.7% placebo), equalizing to 5.1% in both groups by years 2-4 2
• These side effects are typically reversible and become less common after the first year 3

Clinical Considerations for BPH

• Finasteride provides greater benefit in men with larger prostates and/or higher baseline PSA values 3
• For immediate symptom relief in severe cases, consider combination therapy with an alpha-blocker, which is more effective than finasteride monotherapy 3
• Finasteride reduces the risk of acute urinary retention and need for BPH-related surgery compared to placebo (6.6% vs 2.8% for acute retention; 10.1% vs 4.6% for surgical intervention) 2