Safety and efficacy of silodosin for the treatment of benign prostatic hyperplasia

Masaki Yoshida¹, Junzo Kudoh², Yukio Homma³, Kazuki Kawabe^4
1Department of Medical Informatics, ²Department of Urology, Japan Labor Health and Welfare Organization, Kumamoto Rosai Hospital, Kumamoto, Japan; ³Department of Urology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; ⁴Tokyo Teishin Hospital, Tokyo, Japan

Abstract: Lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) are highly prevalent in older men. Medical therapy is the first-line treatment for LUTS associated with BPH. Mainstays in the treatment of male LUTS and clinical BPH are the α₁-adrenergic receptor antagonists. Silodosin is a new α₁-adrenergic receptor antagonist that is selective for the α_1A-adrenergic receptor. By antagonizing α_1A-adrenergic receptors in the prostate and urethra, silodosin causes smooth muscle relaxation in the lower urinary tract. Since silodosin has greater affinity for the α_1A-adrenergic receptor than for the α_1B-adrenergic receptor, it minimizes the propensity for blood pressure-related adverse effects caused by α_1B-adrenergic receptor blockade. In the clinical studies, patients receiving silodosin at a total daily dose of 8 mg exhibited significant improvements in the International Prostate Symptom Score and maximum urinary flow rate compared with those receiving placebo. Silodosin showed early onset of efficacy for both voiding and storage symptoms. Furthermore, long-term safety of silodosin was also demonstrated. Retrograde or abnormal ejaculation was the most commonly reported adverse effect. The incidence of orthostatic hypotension was low. In conclusion, silodosin, a novel selective α_1A-adrenergic receptor antagonist, was effective in general and without obtrusive side effects. This review provides clear evidence in support of the clinical usefulness of silodosin in the treatment of LUTS associated with BPH.

Keywords: α_1A-adrenoceptor antagonist, silodosin, selective, benign prostatic hyperplasia, lower urinary tract symptoms