Routes of
administration Oral Bioavailability 32% | ATC code G04CA04 (WHO) Protein binding 97% | |
 | ||
Pregnancy
category US: B (No risk in non-human studies)
Not approved for use in women Legal status In general: ℞ (Prescription only) | ||
Silodosin (trade names Rapaflo (USA), Silodyx (Europe and South Africa), Rapilif (India), Silodal (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).
Contents
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.
FDA approved silodosin on October 9, 2008. Silodosin is marketed under the trade names Rapaflo in the US and Silodyx in Europe.
Pharmacology
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.