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

Finasteride Dosing Recommendations

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

Dosing by Indication

BPH Treatment

• Finasteride 5 mg once daily is the established dose for BPH, consistently used across all major clinical trials including PCPT, MTOPS, PLESS, PREDICT, and VA Cooperative studies 1
• This dose is only effective in patients with documented prostatic enlargement (prostate volume >30cc), as finasteride is ineffective in men without enlarged prostates 1, 2
• Patients experience an average 3-point improvement in the AUA Symptom Index, which is generally perceived as a meaningful clinical change 2
• Long-term studies demonstrate sustained symptom score improvements of 3-4 points maintained for 6-10 years 1, 2

Androgenetic Alopecia Treatment

• The American Academy of Dermatology recommends finasteride 1 mg once daily 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
• Efficacy is maintained over 5+ years, but hair loss resumes if treatment is discontinued 1
• The 1 mg dose produces similar DHT suppression and PSA reduction (approximately 50% after 12 months) as the 5 mg dose used for BPH 1

Critical PSA Monitoring Requirement

• 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, 2
• Finasteride reduces serum PSA by approximately 50% after one year of treatment at both doses 1, 3
• In men aged 40-49 years taking 1 mg daily, median PSA decrease is 40%; in men aged 50-60 years, median decrease is 50% 3
• Failure to adjust PSA interpretation is a common pitfall that can delay prostate cancer detection 2

Important Clinical Considerations

Onset of Action and Patient Counseling

• Finasteride has a slower onset of action compared to alpha-blockers; patients should be counseled that symptom improvement for BPH may take several months (typically 3-6 months) 2
• Inadequate treatment duration is a common pitfall—patients may discontinue therapy prematurely before experiencing benefit 2

Side Effects

• Decreased libido occurs in 6.4% of patients in the first year and 2.6% in years 2-4 2
• Ejaculatory dysfunction occurs in 3.7% of patients in the first year and 1.5% in years 2-4 2
• These side effects are typically reversible and become less common after the first year of therapy 2
• Patients should not donate blood until 6 months after last dose due to risk to pregnant females 2

Combination Therapy for BPH

• For patients with very large prostates or severe symptoms, combination therapy with an alpha-blocker may be more effective than finasteride monotherapy 2
• Combination therapy provides both immediate symptom relief (from alpha-blocker) and long-term disease modification (from finasteride) 2

Common Pitfalls to Avoid

• Never prescribe finasteride for BPH in patients without documented prostatic enlargement (prostate volume >30cc)—it is ineffective in this population 1, 2
• Always double the PSA value after 12 months of therapy at either dose when screening for prostate cancer 1, 2, 3
• Do not expect immediate symptom relief—counsel patients about the 3-6 month timeframe for BPH symptom improvement 2
• Monitor for breast changes such as gynecomastia or breast tenderness 2