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

Finasteride Dosing

For benign prostatic hyperplasia (BPH), finasteride 5 mg once daily is the recommended dose, while for androgenetic alopecia (male pattern hair loss), finasteride 1 mg once daily is the standard dose. 1, 2

Dosing by Indication

Benign Prostatic Hyperplasia (BPH)

• Finasteride 5 mg once daily is the established dose for BPH treatment, consistently used across all major clinical trials including PCPT, MTOPS, PLESS, PREDICT, and VA Cooperative studies 1, 2
• This dose is only effective in patients with documented prostatic enlargement (prostate volume >30cc on imaging), as finasteride is ineffective in men with lower urinary tract symptoms who lack prostatic enlargement 3, 1
• Symptom improvement takes time—patients should be counseled that meaningful benefit may require 6 months of therapy, with an average 3-point improvement in the AUA Symptom Index typically achieved 3, 2
• Long-term studies demonstrate sustained symptom improvements of 3-4 points maintained for 6-10 years with the 5 mg dose 3, 1

Androgenetic Alopecia (Male Pattern Hair Loss)

• The American Academy of Dermatology recommends finasteride 1 mg once daily for treating male pattern hair loss in men aged 18-60 years 1, 4
• Visible improvement typically begins by 12 weeks, with maximal benefit at 1-2 years of continuous treatment 1, 4
• Efficacy is maintained over 5+ years, but hair loss resumes if treatment is discontinued 1, 4
• 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, 5

Critical PSA Monitoring Consideration

• 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, as finasteride reduces serum PSA by approximately 50% after one year of treatment 3, 1, 4, 5
• This adjustment applies equally to both the 1 mg dose for hair loss and the 5 mg dose for BPH 1, 5
• Failure to adjust PSA interpretation is a common pitfall that can delay prostate cancer detection 3

Sexual Side Effects Profile

• Sexual adverse events (decreased libido, ejaculatory dysfunction, erectile dysfunction) occur in approximately 2-4% more patients compared to placebo 4, 2
• For the 5 mg dose in BPH: decreased libido occurs in 6.4% in year 1 (vs 3.4% placebo) and 2.6% in years 2-4 (vs 2.6% placebo) 3, 2
• These side effects are typically reversible upon discontinuation and become less common after the first year of therapy 3, 4

Common Pitfall to Avoid

• Do not prescribe finasteride for BPH in patients without documented prostatic enlargement (prostate volume >30cc), as it is ineffective in this population 3, 1
• Inadequate treatment duration is another common error—patients must understand that finasteride has a slower onset of action compared to alpha-blockers, requiring several months for symptom improvement 3