Silodosin

Silodosin (trade names Rapaflo (USA), Silodyx (Europe), Rapilif (India), Silodal (India), Urief (Japan)) is a medication for the symptomatic treatment of benign prostatic hyperplasia. It acts as an α1-adrenoceptor antagonist with high uroselectivity (selectivity for the prostate).

History
Silodosin received its first marketing approval in Japan in May 2006 under the tradename Urief, which is jointly marketed by Kissei Pharmaceutical Co., Ltd. and Daiichi Sankyo Pharmaceutical Co., Ltd.

Kissei licensed the US, Canadian, and Mexican rights for silodosin to Watson Pharmaceuticals, Inc. in 2004.

On February 12, 2008, Watson announced that the New Drug Application submitted to the United States Food and Drug Administration for silodosin has been accepted for filing. FDA approved this drug on October 9th, 2008. Silodosin is marketed under the trade names Rapaflo in the US and Silodyx in Europe. and Rapilif in India (Ipca Urosciences)

Pharmacology
Since silodosin is a highly selective inhibitor of the α1A adrenergic receptor, it causes practically no orthostatic hypotension (in contrast to other α1 blockers). On the other side, the high selectivity seems to cause more problems with ejaculation.

As α1A adrenoceptor antagonists are being investigated as a means to male birth control due to their ability to inhibit ejaculation but not orgasm, a trial with 15 male volunteers was conducted. While silodosin was completely efficacious in preventing the release of semen in all subjects, 12 out of the 15 patients reported mild discomfort upon orgasm. The men also reported the psychosexual side effect of being strongly dissatisfied by their lack of ejaculation.