What is the recommended dosage and treatment duration for Finasteride (Finasteride) in treating benign prostatic hyperplasia (BPH) and androgenetic alopecia?

Finasteride Dosing and Treatment Duration

For benign prostatic hyperplasia (BPH), finasteride 5 mg daily is the established dose with indefinite continuation as long as benefit persists, while for androgenetic alopecia, finasteride 1 mg daily should be used with the understanding that treatment must continue indefinitely to maintain hair growth. 1, 2

Dosing by Indication

Benign Prostatic Hyperplasia (BPH)

• Finasteride 5 mg once daily is the standard dose for BPH treatment 1, 2
• This dose was consistently used across all major clinical trials including PCPT, MTOPS, and PLESS 1
• The medication should only be prescribed to men with documented prostatic enlargement (prostate volume >30cc), as finasteride is completely ineffective in patients without enlarged prostates 1, 3

Androgenetic Alopecia (Male Pattern Hair Loss)

• Finasteride 1 mg once daily is the recommended dose for hair loss in men aged 18-60 years 1
• Visible improvement typically begins by 12 weeks, with maximal benefit achieved 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

Treatment Duration

For BPH

• Treatment should be continued indefinitely as long as clinical benefit persists 3, 2
• Long-term studies demonstrate sustained symptom score improvements of 3-4 points maintained for 6-10 years with finasteride 1, 3
• Symptom improvement may take several months, with statistically significant improvement evident at 1 year and continuing through Year 4 2
• A therapeutic trial of at least 6 months is generally necessary to assess whether a beneficial response has been achieved 2

For Androgenetic Alopecia

• Treatment must continue indefinitely to maintain efficacy, as hair loss resumes if treatment is discontinued 1
• Efficacy is maintained over 5+ years of continuous treatment 1, 5
• Discontinuation results in return of DHT levels to pretreatment levels in approximately 2 weeks 2

Critical Clinical Considerations

PSA Monitoring Requirements

• 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, 4
• Finasteride reduces serum PSA by approximately 50% after one year of treatment at both doses 1, 4
• Men aged 40-49 years on 1 mg finasteride show a median 40% decrease in PSA, while men aged 50-60 years show a 50% decrease 4
• Failure to adjust PSA interpretation is a common and dangerous pitfall 3

Expected Clinical Response

BPH Response Timeline

• Patients experience an average 3-point improvement in the AUA Symptom Index, which is generally perceived as a meaningful clinical change 3
• Alpha-blocker response should be assessed at 2-4 weeks, while 5-ARI (finasteride) response requires assessment at minimum 6 months 3
• Finasteride has a slower onset of action compared to alpha-blockers; patients must be counseled that symptom improvement may take several months 3

Prostate Size Reduction

• Finasteride reduces prostate size by 15-25% within 6 months by reducing DHT in the prostate by approximately 70% 3
• Upon discontinuation, prostate volume returns to close to baseline after approximately three months 2

Common Side Effects

Sexual Side Effects (most common adverse reactions):

• Decreased libido: 6.4% in first year, 2.6% in years 2-4 3, 2
• Ejaculatory dysfunction: 3.7% in first year, 1.5% in years 2-4 3, 2
• Impotence: 8.1% in first year, 5.1% in years 2-4 2
• Decreased ejaculate volume: 3.7% in first year, 1.5% in years 2-4 2
• These side effects are typically reversible and become less common after the first year of therapy 3

Other Side Effects:

• Gynecomastia: 0.5% in first year, 1.8% in years 2-4 2
• Breast tenderness: 0.4% in first year, 0.7% in years 2-4 2

Critical Pitfalls to Avoid

1. Never prescribe finasteride for BPH in patients without documented prostatic enlargement (prostate volume >30cc) - it is completely ineffective in this population 1, 3

2. Inadequate treatment duration - finasteride has a slower onset than alpha-blockers; counsel patients that improvement may take several months 3

3. Failure to adjust PSA values - always double the measured PSA after 12 months of therapy at any dose 1, 3, 4

4. Premature discontinuation for hair loss - patients must understand that hair loss will resume if treatment stops 1

Combination Therapy Considerations

• For BPH with severe symptoms or very large prostates, combination therapy with an alpha-blocker plus finasteride is superior to monotherapy 3
• Combination therapy prevents progression of LUTS/BPH, reduces risk of acute urinary retention, and reduces need for future prostate-related surgery 3
• In the MTOPS study, combination therapy showed higher rates of certain adverse effects (asthenia, postural hypotension, dizziness, abnormal ejaculation) compared to monotherapy 2