Silodosin is a selective antagonsit of alpha-1a adrenergic receptor which was developed by Kissei Pharmaceutical. The drug was approved by FDA under the name Rapaflo for the treatment of signs and symptoms associated with benign prostatic hyperplasia.

Tamsulosin, a sulfamoylphenethylamine-derivative alpha-adrenoceptor blocker with enhanced specificity for the alpha-adrenoceptors of the prostate, is commonly used to treat benign prostatic hyperplasia (BPH). The drug is commercially available in a racemic mixture of 2 isomers, and is pharmacologically related to doxazocin, prazosin, and terazosin. However, unlike these drugs, tamsulosin has a higher affinity for the alpha-1A- adrenergic receptors, which are located in vascular smooth muscle. Studies show that tamsulosin has about 12 times greater affinity for alpha-1 adrenergic receptors in the prostate than those in the aorta, which may result in a reduced incidence of adverse cardiovascular effects. Tamsulosin is sold under the trade name Flomax.

KMD-3241 (Dehydro Silodosin) is a silodosin metabolite (also known as an impurity of Silodosin). Silodosin is a selective antagonsit of alpha-1a adrenergic receptor which was developed by Kissei Pharmaceutical and approved by FDA under the name Rapaflo for the treatment of signs and symptoms associated with benign prostatic hyperplasia. The affnities of silodosin metabolites, KMD-3241, KMD-3289 and KMD-3295, for alpha1A-AR subtype receptor were equal to or lower than that of silodosin.