Inhibition of Seminal Emission Is the Main Cause of Anejaculation Induced by a New Highly Selective α1A-Blocker in Normal Volunteers


Ko Kobayashi, Department of Urology, School of Medicine, Sapporo Medical University, S1W16, Chuo-ku, Sapporo, Hokkaido, 060-8543, Japan. Tel: 81-(0)11-611-2111; Fax: 81-(0)11-612-2709; Email:


Introduction.  Recent studies have highlighted the influence of α1-adrenoceptor antagonists on ejaculatory function.

Aim.  We evaluated the effect of a new, highly selective α1A-blocker, silodosin, on ejaculatory function of normal volunteers.

Methods.  The study included 15 healthy male urologists who voluntarily participated in the study. They took 4 mg of silodosin or a placebo twice daily for 3 days in a randomized, double-blind crossover design.

Main Outcome Measures.  We investigated the ejaculatory volume, sperm count in urine after ejaculation, and fructose concentration in seminal plasma before and after administration of the agents.

Results.  All volunteers on silodosin had a complete lack of ejaculation. Three days after completion of silodosin, the mean ejaculatory volume recovered to the baseline level. There was no sperm in urine after ejaculation under silodosin administration in any volunteer.

Conclusions.  All volunteers on silodosin had anejaculation and did not show post-ejaculate sperm in their urine. The mechanism of ejaculatory dysfunction caused by silodosin is a loss of seminal emission. Kobayashi K, Masumori N, Hisasue S, Kato R, Hashimoto K, Itoh N, and Tsukamoto T. Inhibition of seminal emission is the main cause of anejaculation induced by a new highly selective α1A-blocker in normal volunteers. J Sex Med 2008;5:2185–2190.