A Randomized Controlled Study of the Efficacy of Tamsulosin Monotherapy and its Combination with Mirabegron for Overactive Bladder Induced by Benign Prostatic Obstruction

Purpose: We evaluated the efficacy and safety of add-on treatment with a beta(3)-adrenoceptor agonist (mirabegron) for overactive bladder symptoms remaining after alpha(1)-blocker (tamsulosin) treatment in men with benign prostatic obstruction. Materials and Methods: Patients with benign prostatic obstruction with urinary urgency at least once per week and a total OABSS of 3 or more points after 8 or more weeks of treatment with tamsulosin were enrolled in the study. They were randomly allocated to receive 0.2 mg tamsulosin daily or 0.2 mg tamsulosin and 50 mg mirabegron daily for 8 weeks. The primary end point was change in total OABSS. Safety assessments included change in post-void residual urine volume and adverse events. Results: From January 2012 through September 2013 a total of 94 patients were randomized. Of these patients 76 completed the protocol treatment. In the full analysis set the change in total OABSS during the treatment period was significantly greater in the combination group than in the monotherapy group (2.21 vs -0.87, p=0.012). The changes in scores for urinary urgency, daytime frequency, International Prostate Symptom Score storage symptom subscore and quality of life index at 8 weeks were significantly greater in the combination group. The change in post-void residual urine volume was significantly greater in the combination group. Although 6 patients experienced adverse events in the combination group, urinary retention was observed in only 1 patient. Conclusions: Combined tamsulosin and mirabegron treatment is effective and safe for patients with benign prostatic obstruction who have overactive bladder symptoms after tamsulosin monotherapy.