How Finasteride Works on the Prostate
Finasteride (brand name Proscar) is a 5-alpha reductase inhibitor that blocks the enzyme converting testosterone into dihydrotestosterone (DHT). As DHT stimulates prostate growth, lowering its levels with finasteride helps shrink an enlarged prostate, which is beneficial for benign prostatic hyperplasia (BPH) and reducing associated complications.
Success Rate for Benign Prostatic Hyperplasia (BPH)
Finasteride has been shown to improve BPH symptoms and slow its progression, particularly in men with larger prostates.
- Symptom Improvement: Studies like the MTOPS trial show finasteride significantly reduces symptoms compared to placebo in men with larger prostates (30 mL or more). A 6-year study also demonstrated about a 30% improvement in urinary symptom scores, maintained over time.
- Prostate Shrinkage: Finasteride typically reduces prostate volume by 20–25% within 6 to 12 months, with the most significant effect in men with larger prostates (>25-30 mL).
- Reduced Risk of Progression: The PLESS study showed long-term finasteride significantly reduced the risk of acute urinary retention by 57% and BPH-related surgery by 55% compared to placebo.
Finasteride and Prostate Cancer Prevention
Research, especially the Prostate Cancer Prevention Trial (PCPT), has explored finasteride's effect on prostate cancer.
- Reduced Overall Risk: The PCPT found finasteride reduced the overall risk of prostate cancer by about 25–30%, mainly low-grade types.
- Increased Detection of High-Grade Cancer: An initial finding of more high-grade cancers in the finasteride group was later attributed to detection bias, as prostate shrinkage made existing cancers easier to find. A follow-up confirmed no difference in overall survival.
Finasteride vs. Dutasteride Comparison
Finasteride and dutasteride are both 5-alpha reductase inhibitors for BPH but differ in mechanism and DHT suppression. Finasteride blocks type 2, while dutasteride blocks both type 1 and 2.
| Feature | Finasteride (Proscar) | Dutasteride (Avodart) |
|---|---|---|
| Mechanism | Inhibits type 2 5-alpha reductase | Inhibits type 1 and 2 5-alpha reductase |
| DHT Suppression | Suppresses serum DHT by approximately 70% | Suppresses serum DHT by approximately 93% |
| Prostate Volume Reduction | Approximately 20–25% | Up to 25–27% in some studies |
| Onset of Effect | Can take 6–12 months for full symptomatic effect | Possibly a slightly quicker onset of symptomatic relief, but long-term results are key |
| BPH Complication Reduction | Significantly reduces risk of AUR and BPH-related surgery | Significantly reduces risk of AUR and BPH-related surgery |
| Symptom Improvement | Comparable to dutasteride, though some studies suggest a slight advantage for dutasteride in Qmax | Comparable to finasteride |
Factors Influencing the Success Rate of Finasteride
Several factors affect how well finasteride works.
- Prostate Gland Size: Finasteride is most effective in men with larger prostates (e.g., >30-40 mL). Men with smaller prostates may not benefit as much.
- Long-Term Adherence: Consistent daily use is essential, as stopping the medication diminishes results and allows the prostate to regrow.
- Duration of Treatment: Full BPH symptom relief can take at least six months, with benefits sustained over years with continued use.
- Combination Therapy: Combining finasteride with an alpha-blocker can be more effective for men with moderate to severe symptoms and larger prostates, providing faster relief alongside long-term prostate shrinkage.
- Patient Expectations: Setting realistic expectations is important. Finasteride manages BPH and prevents complications but does not cure it.
Conclusion
Finasteride is highly successful for men with enlarged prostates due to BPH, providing long-term benefits in reducing prostate size, improving urinary symptoms, and preventing complications like urinary retention and surgery. Its success relies on consistent, long-term use and is most pronounced in men with larger prostates. While it reduces the risk of low-grade prostate cancer, potential risks and benefits should be discussed. Patient adherence and realistic expectations are crucial for good outcomes. More information on finasteride is available from the Mayo Clinic.
