Mirabegron is a selective beta 3-adrenoceptor agonist which relaxes smooth muscle in the bladder, enhancing urine storage. Marketed in the UK as Betmiga, it is licensed for the symptomatic treatment of urinary frequency, urgency and urge incontinence associated with overactive bladder.
Current NICE guidance recommends pharmacological treatment for OAB only if symptoms persist and frequency is a troublesome symptom following at least 6 weeks of bladder training. It recommends use of an anticholinergic drug first-line, specifically oxybutynin (immediate release), tolterodine (immediate release) or darifenacin (once daily preparation). Use of mirabegron is recommended only if an anticholinergic is contraindicated, ineffective or not tolerated.
The researchers conducted a systematic review of prospective and retrospective observational database studies (n=30) investigating oral treatment of OAB with anticholinergics and/or mirabegron in order to determine the rates and determinants of persistence and adherence.
Medication possession rate (MPR) or proportion of days covered (PDC) by prescription were used as a measure of medication adherence. Persistence was typically defined as the proportion of patients continuing therapy/refilling prescriptions for the follow-up period (without discontinuing the index drug or switching to other OAB drug/s) and/or the median time to discontinuation.
At 1 year, persistence rates for anticholinergics across 19 studies ranged from around 5% to 47%. In the three studies reporting data for anticholinergics and mirabegron 1-year persistence was 12—25% and 32—38%, respectively.
Median time to discontinuation for all anticholinergics across all studies was less than five months (30 to 128 days) with the exception of one study where time to discontinuation was 6.5 months. Median time to discontinuation for mirabegron was 5.6—7.4 months.
In studies reporting adherence for anticholinergics and mirabegron, adherence was significantly higher in patients receiving mirabegron (mean MPR, 0.59 vs 0.41—0.53; mean PDC, 0.66 vs 0.55; median MPR, 0.65 vs 0.19—0.49). The proportion of patients adherent at 1 year was also greater with mirabegron than with anticholinergics (mean MPR ≥0.80: 43% vs 22%—35%; mean PDC ≥0.80, 44% vs 31%).
Reported determinants of persistence and adherence included female sex, older age group, use of extended-release formulation and treatment experience.
The researchers state that, in general, mirabegron was associated with greater persistence and adherence than anticholinergics. They add that when combined with existing clinical trial evidence, this real-world review merits consideration of mirabegron for first-line pharmacological treatment among patients with OAB.