PURPOSE: Long-term persistence with pharmacotherapy for overactive bladder (OAB) 
requires a drug with an early onset of action and good efficacy and tolerability 
profile. Although antimuscarinics improve OAB symptoms within 1-2 weeks of 
initiating treatment, adherence after 3 months is relatively poor due to 
bothersome side effects (e.g., dry mouth and constipation). Mirabegron, a 
β3-adrenoceptor agonist, has demonstrated significant improvements in key 
symptoms of OAB and good tolerability after 12 weeks in Phase III studies.
METHODS: This was a prespecified pooled analysis of three randomized, 
double-blind, placebo-controlled, 12-week studies, and a Phase II study, to 
evaluate efficacy and tolerability of mirabegron 25 and 50 mg versus placebo. 
The main efficacy endpoints were change from baseline to week 1 (Phase II only), 
week 4, and final visit in mean number of incontinence episodes/24 h, 
micturitions/24 h, and mean volume voided/micturition (MVV).
RESULTS: A significant benefit for mirabegron 25 and 50 mg versus placebo was 
evident at the first assessment point, 4 weeks after initiation of therapy, in 
Phase III studies for incontinence, micturitions, and MVV. The earliest measured 
benefit was after 1 week, in the Phase II study. Quality-of-life parameters also 
significantly improved with mirabegron 25 and 50 mg as early as week 4. 
Significant benefits continued throughout the studies. Mirabegron was well 
tolerated.
CONCLUSIONS: The early onset of action and good overall efficacy and 
tolerability balance that mirabegron offers may lead to high rates of 
persistence with mirabegron in the long-term treatment of OAB.