Tolerability and persistence in a large, prospective case series of women prescribed mirabegron

Most published data on mirabegron relates to short-term clinical trials and suggest that it might be effective in controlling OAB and have low side effects. This study aimed to identify persistence with mirabegron, changes in symptoms and quality of life, and predictors of perseverance over 1 year.

The study was a large, prospective case series of 354 patients who were prescribed mirabegron for OAB between February 2013 and July 2014. At 1 year, patients filled out patient global impression of improvement, the International Consultation on Incontinence female lower urinary tract symptoms questionnaire (ICIQ-FLUTS) and PFDI questionnaires. The reasons for discontinuing treatment were identified.

Outcomes were available for 88 % of the cohort. Twenty five percent continued mirabegron therapy at 1 year with 26 % "very much better" and 37 % "much better". ICIQ-FLUTS (17.2-13.4; p = 0.002) and urinary distress inventory (UDI) (59.2-44.3; p < 0.001) scores demonstrated significant improvements from baseline (pre-treatment) compared with 1 year. The ICIQ-FLUTS "filling score" increased from 3.55 at 6 weeks to 5.27 at 1 year (p = 0.02) despite continuing mirabegron therapy. The most common causes of discontinuation were lack of efficacy (26 %) and side effects (10 %). Thirty-seven percent of the cohort was taking mirabegron in combination with an anticholinergic. Patients who were treatment naïve were more likely to discontinue mirabegron than those who had previously taken anticholinergics (p = 0.02).

Over two thirds of patients discontinue mirabegron therapy within 1 year. A significant proportion of patients were on combined therapy to control symptoms. The initial improvement in symptom scores seems to deteriorate. The improvements in quality of life are sustained in patients who persist with therapy.