Silodosin, a novel selective alpha 1A-adrenoceptor selective antagonist for the treatment of benign prostatic hyperplasia.

Silodosin is a novel selective alpha(1A)-adrenoceptor (AR) antagonist generated by Kissei Pharmaceutical Co. Ltd. This drug selectively binds to alpha(1A)-AR, which is widely distributed in the prostate, urethra and bladder trigone, involved in their contraction, located at the lower urinary tract. This high selectivity for alpha(1A)-AR contributes to inhibition of sympathetic nerve stimulation and relaxation of smooth muscle tone of the lower urinary tract tissues, resulting in suppression of increase in intraurethral pressure. Clinical data suggested that silodosin showed significant improvement in lower urinary tract symptoms associated with benign prostatic hyperplasia, as well as in quality of life. The improvements were observed in both voiding and storage symptoms. In addition, the clinical effects occurred in the early treatment phase, and were observed not only in mild cases, but also in cases with severe symptoms. Long-term study revealed that the efficacy and safety was sustained for 1 year. Although silodosin showed relatively high incidence rate of abnormal ejaculation, the adverse events associated with lowering of blood pressure were low. This article reviews preclinical and clinical data of silodosin, and introduces the usefulness of the drug for treatment of benign prostatic hyperplasia patients.