|Metabolism||Hepatic glucuronidation (UGT2B7-mediated); also minor CYP3A4 involvement|
|Elimination half-life||13±8 hours|
|Excretion||Renal and fecal|
|CompTox Dashboard (EPA)|
|Chemical and physical data|
|Molar mass||495.534 g/mol g·mol−1|
|3D model (JSmol)|
|(what is this?)|
Silodosin (trade names Rapaflo (USA), Silodyx (Europe and South Africa), Rapilif (India), Silodal (India), Sildoo(India) Urief (Japan), Thrupas (South Korea), Urorec (Russia) 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).
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.
Since silodosin has high affinity for 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 be the cause of silodosin's typical side effect of loss of seminal emission.
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.