Muscarinic Receptor Antagonists, the Overactive Bladder and Efficacy against Urinary Urgency

The overactive bladder (OAB) is a debilitating condition in which patients suffer from urinary urgency, frequency and nocturia with or without urge urinary incontinence. The mainstay of pharmacotherapy for OAB is muscarinic receptor antagonists, which have been shown to be effective treatments for the symptoms of OAB. The mechanism underlying the efficacy of antimuscarinic agents against the symptoms of OAB is not completely understood. This review explores the role of bladder mucosal muscarinic receptors in the signaling pathways that are activated in response to bladder filling. The cholinergic system is seen to be involved in bladder afferent signaling at many levels and as such muscarinic receptor antagonists may affect bladder signaling via numerous pathways including release of mediators from the bladder urothelium and activation of suburothelial myofibroblasts and afferent nerves. Therefore the mucosal cholinergic system may represent another target for the antimuscarinic agents used to treat OAB.