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.

Solifenacin exerts minimal inhibitory effects on salivary and cardiac responses at a dosage of 630 nmol/kg (0.3 mg/kg), achieving inhibition levels of 66% and 49%, respectively, at 2100 nmol/kg (1 mg/kg). At lower doses (63 and 210 nmol/kg or 0.03 and 0.1 mg/kg), Solifenacin slightly enhances saliva secretion. Conversely, it reduces bladder responses by 40% at 210 nmol/kg (0.1 mg/kg) and completely suppresses them at 2100 nmol/kg (1 mg/kg). Intravenously administered, Solifenacin (0.01 to 0.3 mg/kg) progressively augments bladder capacity and the volume of urine voided when dosed at 0.03 mg/kg or higher, without impacting residual volume or micturition pressure at any administered dosage.