Clinical use of the β3 adrenoceptor agonist mirabegron in patients with overactive bladder syndrome.

Mirabegron is a β3 adrenoceptor agonist licensed for the treatment of overactive bladder symptoms, such as urinary urgency or urgency incontinence. β3 adrenoceptor activation causes detrusor muscle relaxation, but mirabegron may also act by binding other targets in the bladder, and it may also reduce activity in sensory nerves. Phase III clinical trials (SCORPIO, ARIES, and CAPRICORN) evaluated mirabegron at various doses, demonstrating reduction from baseline to endpoint in mean incontinence episodes and mean number of micturitions per 24 h (coprimary endpoints), along with health-related quality of life and a range of secondary measures. Efficacy was seen in many patients who had previously discontinued antimuscarinic therapy on the grounds of lack of efficacy or poor tolerability. Treatment emergent adverse effects were documented in a long-term study (TAURUS), mostly being of mild or moderate severity. The most frequent adverse effects were hypertension, dry mouth, constipation, and headache, with a lower incidence of dry mouth than for the antimuscarinic active comparator. Efficacy and safety are not substantially different in older patients. A urodynamic safety study in men showed no consistent effect on voiding function, but a small increase in postvoid residual. Use of mirabegron in combination with α-adrenergic blockers does not appear to increase adverse effects. Dose reduction is needed in people with severe renal failure, or moderate hepatic failure. Dose adjustment is not needed in relation to food intake. Ongoing research is evaluating the potential for combination therapy with antimuscarinics.