Non‐inferiority of Silodosin 4 Mg Once Daily to Twice Daily for Storage Symptoms Score Evaluated by the International Prostate Symptom Score in Japanese Patients with Benign Prostatic Hyperplasia: A Multicenter, Randomized, Parallel‐group Study

ObjectivesTo compare the effect of treatment with silodosin 4 mg once daily versus that of silodosin 4 mg twice daily on storage symptoms in Japanese patients with benign prostatic hyperplasia.MethodsA prospective, multicenter, 12‐week, open‐labeled study randomized a total of 268 men aged 50 years or older with benign prostatic hyperplasia and overactive bladder to silodosin 4 mg/day or 8 mg/day. Changes in the end‐points of the average value of International Prostate Symptom Score, quality of life index in the International Prostate Symptom Score, Overactive Bladder Symptom Score and urodynamic parameters were evaluated. The change in the storage symptom subtotal score of the International Prostate Symptom Score was considered as the primary end‐point.ResultsSilodosin 4 mg/day was not inferior to silodosin 8 mg/day in regard to the primary end‐point. In contrast, the efficacy of treatment with silodosin 4 mg twice daily was greater than that of 4 mg once daily, based on both the quality of life index and the Overactive Bladder Symptom Score total score. There was a discrepancy between the scores evaluated using the International Prostate Symptom Score and Overactive Bladder Symptom Score questionnaires.ConclusionsSilodosin 4 mg once daily is not inferior to silodosin 4 mg twice daily in regard to storage symptoms score evaluated by the International Prostate Symptom Score. In contrast, silodosin 4 mg twice daily is more effective on storage symptoms evaluated by the Overactive Bladder Symptom Score than silodosin 4 mg once daily.