At least 80% of urology patients are taking several medications for any variety of other medical conditions. However, regarding treatment of overactive bladder (OAB) specifically, there are several antimuscarinic drugs available. Tolterodine and trospium chloride are, in essence, nonspecific in terms of muscarinic receptor selectivity. Solifenacin and oxybutynin show selectivity for the M1, and darifenacin is significantly M3 receptor specific (Slide 17).

The potential benefit for selective antimuscarinic agents is that they might target the bladder more specifically and avoid anticholinergic side effects in other organ systems, specifically the brain and heart. We do know that M3 receptors are also present in the intestines and in the salivary glands; thus, we might not expect organ selectivity with an M3-specific receptor because that receptor would also potentially affect the salivary gland and the intestinal tract as well.

There is a growing body of data regarding M3 activity specificity and decreased cognitive impairment in patients of various ages. This, as well as the reduction of cardiac side effects, are the major benefits of using an M3-selective anticholinergic medication rather than a nonselective agent for the treatment of OAB.