KMD 3213(silodosin, KAD 3213) is an orally active alpha(1)-adrenoceptor antagonist.[1] Silodosin shows higher selectivity for the alpha(1A)-AR subtype than tamsulosin hydrochloride, naftopidil or prazosin hydrochloride.Silodosin strongly antagonizes noradrenaline-induced contractions in rabbit lower urinary tract tissues.[2] silodosin inhibits the phenylephrine-induced increase in intraurethral pressure for a longer time than tamsulosin hydrochloride.[3]
In vivo
Silodosin is a dual substrate for CYP3A4 and p-glycoprotein. After a single oral dose of (14)C-silodosin in rat, dog and human, the urinary excretion of radioactivity was 15-34%, with that of unchanged silodosin being less than 4%.[4]Intravenously (i.v.) administered silodosin dose-dependently inhibited the HNS-induced increase in IUP with much less hypotensive effect than either tamsulosin or naftopidil, the uroselectivity (ED(15)/ID(50)) of silodosin (237) being significantly higher than those of tamsulosin (1.21) and naftopidil (2.65).[5]