5 alpha-reductase inhibitors: what's new?

Medical therapy is now the first-line treatment for most men with symptomatic benign prostatic hyperplasia. This review aims to highlight the recent contributions to our understanding of 5 alpha-reductase inhibitor usage.

For the last decade, finasteride has been the only available 5 alpha-reductase inhibitor, acting upon the type 2 isoenzyme of 5-alpha reductase. Dutasteride is the first drug that can inhibit both isoenzymes and is soon to be available. Biochemically it achieves greater and more rapid dihydrotestosterone suppression compared with finasteride. Clinically, it appears to be at least as good in terms of improving symptoms and flow rates, and reducing the risk of acute urinary retention or the requirement for benign prostatic hyperplasia-related surgery. However, until these two drugs are formally compared, the true benefits of additional type 1 isoenzyme inhibition are unknown. The recently reported Medical Therapy of Prostatic Symptoms trial has convincingly demonstrated superior outcomes with combination therapy compared with monotherapy, unlike previous trials of shorter duration. The ability of 5 alpha-reductase inhibitors to prevent disease progression was also confirmed. Newer roles for 5 alpha-reductase inhibitors are also being defined. Finasteride has been shown to reduce and control benign prostatic hyperplasia-related haematuria, although its value in controlling perioperative bleeding is less clear. Their role as chemopreventive agents for prostate cancer is also under investigation.

Recent studies have both clarified and extended the roles of 5 alpha-reductase inhibitors in benign prostatic hyperplasia, and these may expand further if chemopreventive abilities are proved. In addition, dual isoenzyme inhibition will soon be available.