Comparison of clinical trials with finasteride and dutasteride.

Finasteride selectively inhibits the Type 2 isoenzyme of 5alpha-reductase (5AR) (the enzyme responsible for converting testosterone to dihydrotestosterone [DHT]) whereas dutasteride inhibits both Type 1 and Type 2 5AR. General conclusions regarding the differences and similarities of these 2 agents, in terms of pharmacologic effect, safety, and efficacy, can be drawn from evaluation of short-term comparative trials and similar but non-comparative long-term trials. Dutasteride therapy reduces serum DHT significantly more than does finasteride. In men with benign prostatic hyperplasia (BPH), treatment with either agent results in similar prostate gland volume reduction, flow rate and symptom improvement, and similar reductions in long-term risk of BPH development in terms of symptom progression and acute urinary retention (AUR) and BPH-related surgery. There does not appear to be any clinically significant difference between the adverse event profiles of dutasteride and finasteride. Although weak evidence suggests a difference in the onset of clinical benefit, the available non-comparative trial data do not confirm this finding. Patients with symptomatic BPH who receive dutasteride or finasteride, either as monotherapy or combination therapy with alpha-blockers, can expect to experience significant prostate gland size reduction, improved symptoms, and reduced risk of progression in terms of long-term adverse outcomes.