Finasteride for BPH: Treatment Duration & What to Expect

Finasteride 5 mg daily is a long-term treatment for benign prostatic hyperplasia (BPH). It inhibits 5α-reductase type II, reducing intraprostatic DHT by ~70–90%, shrinking the prostate over time.

Timeline of Effects

• 1–3 months: PSA decreases ~50% (adjust interpretation). Symptom improvement may begin.
• 6–12 months: Maximal prostate volume reduction (~20–30%). Significant symptom relief (IPSS), improved flow rate.
• Long-term (≥4 years): Reduces risk of acute urinary retention (AUR) by ~50% and BPH-related surgery by ~50% (MTOPS trial).

Duration

Continued indefinitely while benefits outweigh risks. Discontinuation → prostate regrowth, symptom return within months.

Monitoring

• PSA at baseline, 3–6 months, then annually (multiply by 2 for screening interpretation).
• DRE annually.
• Symptom score (IPSS) periodically.

Side Effects

• Sexual: decreased libido, ED, ejaculatory disorder (~3–5% > placebo).
• Gynecomastia, tenderness.
• Mood changes (rare); high-grade prostate cancer risk debated (PCPT trial).

Discuss risks/benefits with your urologist. Finasteride is not for prostate cancer prevention.