The effect of finasteride on prostate volume, urinary flow rate and symptom score in men with benign prostatic hyperplasia.

This study was designed to determine the efficacy of the 5 alpha-reductase inhibitor finasteride (Proscar, MK-906) in men with reduced urinary flow rates and symptoms of urinary outflow obstruction secondary to benign prostatic hyperplasia. Forty-five men were randomized to one of three groups receiving either placebo, 1 mg/day or 5 mg/day finasteride for the first 12 months of the study period. At the end of this period all men received 5 mg/day finasteride for a further 2 years. Efficacy was determined by measurement of prostate volume, maximum urinary flow rate, and symptom score using a modified Boyarsky assessment. Prostate volume reduced by 20 and 27%, respectively, for those on 1 and 5 mg after the first year. At 3 years the volume had reduced by 43%. This reduction in prostate volume was associated with an improvement in maximum urinary flow rate by 50% (1 mg), and 35% (5 mg) at 1 year, and 36% at 3 years. The total, obstructive and non-obstructive symptom scores decreased (improved) for patients on 1 and 5 mg finasteride, with the total score reducing by 33% from baseline at year 3. The results demonstrate that finasteride causes a modest but significant clinical improvement in men with urinary outflow obstruction secondary to benign prostatic hyperplasia.