Symptomatic benign prostatic hyperplasia: the role of 5-alpha-reductase inhibitors in the prevention of acute urinary retention and surgical therapy

Benign prostatic hyperplasia (BPH) is a disease that affects over 50% of males aged 50 years or older. In men aged >80 years, the incidence is 90%. BPH occurs in 9-25% of males aged 40 to 79 years. Fifty percent of patients with BPH are symptomatic. The symptoms include reduced urinary flow, nocturia, defective bladder emptying, urinary hesitancy, and dysuria. Disease progression can be associated with acute urinary retention (AUR). Prostatic obstruction includes mechanical and dynamic components, the latter mediated by alpha-muscarinic receptors. Treatment with alpha-1-blockers (alfuzosin, doxazosin, tamsulosin, and terazosin) leads to rapid amelioration of symptoms and urinary flow, usually within one or two weeks. The 5-alpha reductase inhibitors (5-ARIs) are disease-modifying drugs. They control the growth of the prostate by blocking the conversion of testosterone into dihydrotestosterone (DHT). Finasteride is a 5-ARI that is selective for type 2 receptors. Dutasteride is a powerful inhibitor of both 5- alpha reductase isoforms (type 1 and 2) and produces more complete suppression of DHT synthesis than finasteride. Dutasteride also has a much longer half-life than finasteride (five weeks versus five to six hours). The authors review the results of clinical trials involving finasteride and dutasteride, with and without alpha-1-blockers, highlighting the important role of dutasteride in improving acute urinary retention and eliminating the need for surgical therapy.