Persistence and adherence with mirabegron vs antimuscarinics in overactive bladder: Retrospective analysis of a UK General Practice prescription database

Introduction and objectives: Persistence with antimuscarinic (AM) drugs prescribed for overactive bladder (OAB) is poor. This study aimed to compare persistence and adherence with the beta-3-adrenoceptor agonist mirabegron (MIR) vs AMs over 12 months. Patients and Methods: This retrospective cohort analysis included patients aged >= 18 years who were prescribed MIR, or any AM. A 12-month look-back was used to assess inclusion eligibility. The primary end-point was persistence, defined as time to first discontinuation of index drug, during 1year follow-up. The secondary end-point was adherence, estimated by medication possession ratio (MPR). Results: Inclusion criteria were met by 6189 patients. Those prescribed AMs were mostly treatment-naive (range 72.9%-95.3%) vs 54.4% of MIR patients. There was greater persistence with MIR vs AM. The median number of days on therapy with MIR was 101, vs 27-56 for AMs. Patients receiving AMs were significantly more likely to discontinue than those receiving MIR (hazard ratio [HR] range 1.24-2.05, P<.01 for each AM vs MIR. In treatment-naive patients, HRs ranged from 1.25 (solifenacin, P=.012) to 2.07 (oxybutynin IR, P<.001). In treatment-experienced patients, they ranged from 1.10 (fesoterodine, P=NS) to 2.12 (oxybutynin IR, P<.001). Adherence was greater with MIR (mean MPR 48.4%) than with AMs (range 27.6%-40.4%, P<.001). Treatment-experienced patients were significantly less likely to discontinue treatment (HR 0.87, P=.006). Discussion and conclusion: MIR was associated with a significantly longer time to discontinuation, greater persistence and better adherence than AMs. However, there was a steep decline in persistence with all drugs after 1 month. This is unlikely to be wholly explained by anticholinergic adverse events, as it was also seen with MIR. The lower proportion of MIR patients who were treatment-naive reflects current prescribing guidelines whereby MIR is prescribed after an initial generic AM trial. The study was limited by the small number of MIR patients.