Elevating our therapeutic expectations in overactive bladder.

Drug therapy for overactive bladder (OAB) most commonly includes antimuscarinic agents, which work by relaxing bladder smooth muscle through inhibition of acetylcholine receptors in the bladder. The major adverse effects with existing antimuscarinic agents are anticholinergic in nature (e.g., dry mouth, constipation, blurred vision). Oxybutynin and tolterodine have been used for several years for treatment of OAB; both are available in immediate- and extended-release formulations. Fewer or less severe adverse effects are reported with the extended- versus the immediate-release formulations, with little or no difference in efficacy. Oxybutynin is also available as a transdermal patch. Trospium, which was recently approved for use in the United States, has efficacy and an incidence of dry mouth similar to existing agents but does not cross the blood-brain barrier. It requires twice-daily dosing. Two new antimuscarinic agents--darifenacin and solifenacin--are in development. Both show significantly better efficacy compared with placebo for key symptoms of OAB, including urgency. The incidence of dry mouth at the lowest effective dose is 19% for darifenacin and 8% and 14% for solifenacin (2 studies).