Silodosin versus naftopidil in Japanese patients with lower urinary tract symptoms associated with benign prostatic hyperplasia: a randomized multicenter study

Abstract

Objectives: Silodosin is a novel drug that is highly selective to subtype alpha 1A and, since 2006, has been used in Japan for treating benign prostatic hyperplasia. This study aimed to compare the clinical effects of the alpha-adrenoceptor antagonist, silodosin, with those of naftopidil in patients presenting lower urinary tract symptoms associated with benign prostatic hyperplasia.

Methods: This was a randomized, open-label, controlled multicenter study carried out in Japan. Overall, 121 participants with lower urinary tract symptoms associated with benign prostatic hyperplasia were randomized to receive silodosin (4 mg twice daily) or naftopidil (50 mg once daily) for 4 or 8 weeks. Patients were divided into four groups: the alpha-blocker-naive groups received silodosin (35 patients) or naftopidil (33 patients) and the drug-switching groups changed from tamsulosin to silodosin (26 patients) or naftopidil (27 patients). The outcomes parameters were the International Prostate Symptom Score, quality of life, maximum urinary flow rate and post-void residual urine volume. P < 0.05 was considered statistically significant by using the Wilcoxon signed-rank and rank-sum tests, and analysis of covariance.

Results: In all the groups, silodosin and naftopidil significantly improved the total International Prostate Symptom Score and quality of life. However, silodosin obtained significantly better improvement in total International Prostate Symptom Score in the alpha-blocker-naive patients at 4 and 8 weeks. The maximum urinary flow rate and residual urine did not change significantly in all the treatment groups.

Conclusions: The present study confirms the clinical usefulness of silodosin in the treatment of lower urinary tract symptoms associated with benign prostatic hyperplasia.

Keywords: benign prostatic hyperplasia; lower urinary tract symptoms; naftopidil; silodosin.