Solifenacin (YM905 free base) (YM905 free base) is a novel muscarinic receptor antagonist, its pKis for M1, M2 and M3 receptors is of 7.6, 6.9 and 8.0, respectively.

M3 mAChR:8 (ki), M2 mAChR:6.9 (ki), M1 receptor:7.6 (ki)

The inhibitory effects of Solifenacin on salivary and cardiac responses are only slight at 630 nmol/kg (0.3 mg/kg), and reach 66% and 49%, respectively, at 2100 nmol/kg (1 mg/kg). Solifenacin slightly increases saliva secretion at doses of 63 and 210 nmol/kg (0.03 and 0.1 mg/kg). However, Solifenacin reduces bladder responses by 40% at a dose of 210 nmol/kg (0.1 mg/kg) and abolishes them at 2100 nmol/kg (1 mg/kg). Solifenacin (0.01 to 0.3 mg/kg i.v.) dose-dependently increases bladder capacity and voided volume at doses of 0.03 mg/kg i.v. or more, but does not affect residual volume or micturition pressure at any dose tested.