Mirabegron

Mirabegron (YM-178) is the first β3-adrenoceptor agonist that is clinically effective for overactive bladder. Mirabegron (0.3 and 1 mg/kg) inhibits mechanosensitive single-unit afferent activities (SAAs) of Aδ fibers in response to bladder filling. Mirabegron activates the β3 adrenergic receptor in the detrusor muscle in the bladder, which leads to muscle relaxation and an increase in bladder capacity. Mirabegron (YM-178) acts partly as an irreversible or quasi-irreversible metabolism-dependent inhibitor of CYP2D6. Mirabegron at a dose of 3 mg/kg i.v. decreased the frequency of rhythmic bladder contraction induced by intravesical filling with saline without suppressing its amplitude in anesthetized rats. Mirabegron decreases primary bladder afferent activity and bladder microcontractions in rats. Mirabegron (YM-178) also reduced non-micturition bladder contractions in an awake rat model of bladder outlet obstruction.