Antimuscarinic medications have long been the mainstay of drug treatment for 
overactive bladder. This article describes mirabegron, one of a new class of 
agents that relaxes the detrusor muscle directly via a beta3 adrenoceptor 
agonist. Mirabegron's efficacy on frequency, urgency, and urge incontinence was 
tested in several trials before its wide clinical introduction. However, caution 
is still needed as data are lacking on the drug's efficacy and safety in frail 
older adults and for long-term therapy.