One-year experience in the treatment of benign prostatic hyperplasia with finasteride. The MK-906 (Finasteride) Study Group.

Finasteride (MK-906) is a 5 alpha-reductase inhibitor that reduces circulating dihydrotestosterone (DHT) levels without lowering testosterone levels. The goal of this study was to evaluate the effects of long-term (12 months) treatment with finasteride in 67 men with benign prostatic hyperplasia to determine if previously reported short-term efficacy was maintained with chronic therapy. Treatment with 10 mg of finasteride resulted in a 78% to 80% reduction in DHT levels (P less than 0.001) levels, and a small but significant increase in testosterone levels (P less than 0.05) that were maintained over the 12-month period. Significant reduction in prostate volume was observed after 6 months of treatment and maintained at month 12 (P less than 0.05). In patients with baseline maximum flow rates less than or equal to 15 ml/second, maximum urinary flow significantly increased by a mean of 4 ml/second (P less than 0.01), with at least a 3 ml/second improvement observed in up to 70% of the patients at month 12. These results indicate that finasteride can reduce prostate size and improve maximum urinary flow with no loss of efficacy after 1 year of treatment. It is concluded that finasteride has the potential to be an effective chronic therapy for benign prostatic hyperplasia.