β3-receptor agonists for overactive bladder--new frontier or more of the same?

The new information generated over the last decade on the physiology/pharmacology of the normal bladder and on the pathophysiology of the overactive bladder has resulted in the introduction of a new therapeutic principle, β3-adrenoceptor (AR) agonism, and the approval of mirabegron, a selective agonist at β3-ARs. It may be asked in what respects the β3-AR agonists as a group, and mirabegron in particular, differ from the antimuscarinics, and what can clinically be gained by the β3-AR agonists. In this short review, the mechanisms of action, clinical efficacy, and adverse effect profiles of the two groups of drugs are compared and discussed.