266 Objective efficacy of mirabegron on storage and voiding function in patients with over-active bladder that are unresponsive to antimuscarinic treatment, based on a urodynamic study

Abstract

INTRODUCTION AND OBJECTIVES: Oral anti-muscarinic agents are currently the mainstay pharmacotherapy for the treatment of overactive bladder (OAB). However, some patients experience insufficient improvement or adverse events such as dry mouth and constipation. Such patients either persist with the unsatisfactory treatment or discontinue therapy. Mirabegron is a novel, first-in-class selective b3-adrenoceptor agonist. The results of the phase III clinical trials performed in the US, Europe, and Japan using this agent have reported to relieve subjective symptoms associated with OAB. However, the evidence proving that, this drug is effective for OAB that is unresponsive to antimuscarinic treatment is absent. We investigated the objective effectiveness of mirabegron for patients with OAB that cannot be managed with antimuscarinics METHODS: In this prospective study, 50 OAB female patients already treated with antimuscarinic agents having poor therapeutic effects (OAB symptom scores (OABSS) of 3 and 1 urgency episodes a week). The patients stop taking antimuscarinics and after 2weeks wash out, received 50 mg mirabegron once a day for 12 weeks. The OABSS was conducted before and after mirabegron administration to evaluate subjective symptom severity. In this UDS, we assessed the first desire to void (FDV), maximum cystometric capacity (MCC), and occurrence of uninhibited detrusor contraction as parameters of storage function. Maximum flow rate and detrusor pressure at Qmax were assessed as parameters of voiding function. RESULTS: The patients0 mean age was 71.3 years. Between preand post-administration, the mean OABSS score decreased from 8.3 to 4.9 points (p < 0.001), indicating significant improvement of subjective symptoms. From the UDS results, we observed a statistically significant improvement in the storage function parameters, with mean FDV and MCC. Although uninhibited detrusor contraction was observed in 32 patients (64%) before administration, no contraction was observed in 15 of these 32 patients (46.9%) after administration (p 1⁄4 0.01). On voiding function, mirabegron does not inhibit voiding function. Treatment was discontinued in only 1 patient (2.5%) because of the adverse reaction. CONCLUSIONS: Mirabegron was shown to be effective in women with OAB that is unresponsive to antimuscarinic treatment in terms of both subjective symptoms and bladder storage function. In addition,the incidence of side effects is low. Mirabegron may be a new therapeutic alternative for treating OAB.