What is the recommended use and dosage of Finasteride (finasteride) for benign prostatic hyperplasia (BPH) and androgenetic alopecia (male pattern baldness)?

Finasteride: Recommended Use and Dosage

Benign Prostatic Hyperplasia (BPH)

Finasteride 5 mg daily is indicated for men with lower urinary tract symptoms (LUTS) who have documented prostatic enlargement greater than 30cc on imaging. 1, 2

Patient Selection Criteria

• Only prescribe finasteride for BPH in patients with prostate volume >30cc - it is ineffective in men without prostatic enlargement 1, 2
• Finasteride provides greater benefit in men with larger prostates and/or higher PSA values 1, 2
• Patients should have moderate to severe symptoms (AUA Symptom Score typically ≥8) 3

Dosing and Administration

• Standard dose: 5 mg once daily 3
• Patients require at least 6 months of therapy to assess therapeutic benefit, as finasteride has a slower onset of action compared to alpha-blockers 1, 3
• Symptom improvement typically becomes evident after 3-6 months 1

Expected Clinical Outcomes

• Average 3-point improvement in AUA Symptom Index, which is clinically meaningful 1, 3
• 15-25% reduction in prostate size within 6 months 1, 2
• Long-term studies demonstrate sustained symptom improvements maintained for 6-10 years 1, 2
• Reduces risk of acute urinary retention by 57% (2.8% vs 6.6% with placebo) 3
• Reduces need for BPH-related surgery by 55% (4.6% vs 10.1% with placebo) 3

Critical PSA Monitoring Consideration

• Finasteride reduces serum PSA by approximately 50% after 12 months of therapy 1, 2
• When screening for prostate cancer, double the measured PSA value after 1 year of finasteride therapy 1, 2
• Failure to adjust PSA interpretation is a common and serious pitfall 1

Side Effects

• Decreased libido: 6.4% in first year, 2.6% in years 2-4 1, 3
• Ejaculatory dysfunction: 3.7% in first year, 1.5% in years 2-4 1, 3
• Impotence: 8.1% in first year, 5.1% in years 2-4 3
• Gynecomastia: 0.5% in first year, 1.8% in years 2-4 3
• These side effects typically become less common after the first year and are generally reversible 1, 3

Combination Therapy

• Combination therapy with finasteride 5 mg plus an alpha-blocker (e.g., tamsulosin 0.4 mg) is more effective than either monotherapy alone for men with moderate-to-severe LUTS and enlarged prostates 1, 2, 4
• The combination reduces overall BPH clinical progression by 67% compared to 39% for alpha-blockers alone and 34% for finasteride alone 4
• Consider combination therapy for patients with very large prostates or severe symptoms requiring more immediate relief 1, 2

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Androgenetic Alopecia (Male Pattern Baldness)

Finasteride 1 mg daily is approved for the treatment of male pattern hair loss in men. 5

Dosing and Administration

• Standard dose: 1 mg once daily 6, 5
• This lower dose (1 mg) is distinct from the 5 mg dose used for BPH 6, 5

Mechanism and Efficacy

• Inhibits type II 5α-reductase, preventing conversion of testosterone to dihydrotestosterone (DHT) 5
• Reduction in DHT results in significant improvement in hair growth and density 5
• Well-tolerated with favorable adverse event profile 5

Critical PSA Consideration for Alopecia Patients

• Men aged 40-60 years taking 1 mg finasteride for hair loss experience a 40-50% median decrease in serum PSA within 48 weeks 6
• The existing recommendation to double PSA values for prostate cancer screening applies equally to men taking 1 mg finasteride for alopecia, not just those taking 5 mg for BPH 6
• This is a frequently overlooked clinical pitfall that can delay prostate cancer diagnosis 6

Common Side Effects

• Reduced libido 5
• Decreased ejaculate volume 5
• Gynecomastia 5

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Important Safety Considerations Across Both Indications

High-Grade Prostate Cancer Risk

• The Prostate Cancer Prevention Trial (PCPT) found a higher incidence of Gleason score 8-10 prostate cancer in men treated with finasteride 5 mg (1.8%) compared to placebo (1.4%) 3
• This finding remains controversial regarding whether it represents a real increase or detection bias 7

Post-Finasteride Syndrome

• A small subgroup of patients may experience persistent sexual, neurological, psychiatric, and metabolic side effects even after discontinuing finasteride 8
• This syndrome has serious quality of life implications without clear etiology or established therapy 8

Special Population: Men on Testosterone Supplementation

• Finasteride can be safely used in men on testosterone supplementation for BPH/LUTS, as it specifically targets prostatic DHT without lowering serum testosterone to castration levels 1
• Confirm prostatic enlargement (>30cc) before initiating finasteride in this population 1