Can finasteride help Benign Prostatic Hyperplasia (BPH) with Lower Urinary Tract Symptoms (LUTS) without stopping testosterone supplementation?

Finasteride for BPH with LUTS in Patients on Testosterone Supplementation

Finasteride is an appropriate and effective treatment for BPH with LUTS in patients on testosterone supplementation, as it specifically blocks the conversion of testosterone to dihydrotestosterone in the prostate without affecting serum testosterone levels. 1, 2

Mechanism of Action and Rationale

• Finasteride inhibits the 5-alpha-reductase type II isoenzyme, reducing dihydrotestosterone (DHT) in the prostate by approximately 70%, leading to a 15-25% reduction in prostate size within 6 months 2
• Finasteride does not lower serum testosterone to castration levels, making it compatible with testosterone supplementation 1
• The medication specifically targets the conversion of testosterone to DHT in prostatic tissue, allowing testosterone supplementation to continue while addressing prostate enlargement 1, 2

Efficacy for BPH with LUTS

• Finasteride provides an average 3-point improvement in the AUA Symptom Index, which is generally perceived as a meaningful clinical change 1, 2
• Finasteride significantly reduces the risk of acute urinary retention (by 67%) and the need for BPH-related surgery (by 64%) compared to placebo 3
• Long-term studies demonstrate symptom score improvements of 3-4 points maintained for 6-10 years with finasteride therapy 2
• Finasteride is FDA-approved for treatment of symptomatic BPH to improve symptoms, reduce risk of acute urinary retention, and reduce need for surgery 3

Important Patient Selection Criteria

• Finasteride is most effective in patients with demonstrable prostatic enlargement (prostate volume >30cc) 1, 2
• Finasteride is ineffective in patients who do not have enlarged prostates 1
• Patients with larger prostates and/or higher PSA values derive greater benefit from finasteride therapy 1, 2

Potential Side Effects

• Sexual side effects include decreased libido (6.4% in first year, 2.6% in years 2-4), ejaculatory dysfunction (3.7% in first year, 1.5% in years 2-4), and erectile dysfunction 2, 4
• These side effects are typically reversible and become less common after the first year of therapy 1, 2
• Some studies suggest finasteride may worsen erectile dysfunction and potentially reduce total testosterone levels with long-term use 4
• A small subgroup of patients may experience persistent sexual side effects even after discontinuing the medication (post-finasteride syndrome) 5

Combination Therapy Considerations

• Combination therapy with an alpha-blocker and finasteride is more effective than finasteride alone for immediate symptom relief 1, 6
• The combination of finasteride with doxazosin reduces the risk of symptomatic progression of BPH by 67% compared to placebo 3
• Alpha-blockers provide faster symptom relief, while finasteride offers long-term benefits in reducing disease progression 2, 6

Clinical Pearls and Pitfalls

• PSA levels decrease by approximately 50% after 12 months of finasteride therapy; measured PSA should be doubled for accurate assessment 2
• Patients should be counseled that symptom improvement may take several months, as finasteride has a slower onset of action compared to alpha-blockers 2
• Finasteride can be used as monotherapy after an initial period of combination therapy with an alpha-blocker, maintaining symptom control for at least 9 months 7

Algorithm for Treatment

1. Confirm prostatic enlargement (>30cc) before initiating finasteride 1, 2
2. For immediate symptom relief, consider starting with combination therapy (finasteride + alpha-blocker) 1, 3
3. Monitor for sexual side effects, especially in the first year of treatment 2, 4
4. Continue testosterone supplementation as finasteride specifically targets prostatic DHT without affecting serum testosterone 1, 2
5. Adjust PSA interpretation by doubling the measured value after 12 months of therapy 2
6. Consider transitioning to finasteride monotherapy after 9 months of combination therapy if symptoms are well-controlled 7