Drug Interactions: Inhibitors of CYP3A4 may increase the concentration of UROCALM.
Inducers of CYP3A4 may decrease the concentration of UROCALM.
Drugs Metabolized by Cytochrome P450: At therapeutic concentrations, solifenacin does not inhibit CYP1A1/2, 2C9, 2C19, 2D6, or 3A4 derived from human liver microsomes.
Pharmacological interactions: The therapeutic effect of Solifenacin may be reduced by concomitant administration of cholinergic receptor agonists.
An interval of approximately one week should be allowed after stopping treatment with Solifenacin, before commencing other anticholinergic therapy.
Solifenacin can reduce the effect of medicinal products that stimulate the motility of the gastro-intestinal tract, such as metoclopramide and cisapride.
Effect of other medicinal products on the pharmacokinetics of solifenacin: Solifenacin is metabolised by CYP3A4. Simultaneous administration of ketoconazole (200 mg/day), a potent CYP3A4 inhibitors resulted in two fold increase of the AUC of Solifenacin. Therefore, the maximum dose of Solifenacin should be restricted to 5 mg, when used simultaneously with ketoconazole or therapeutic doses of other potent CYP3A4 inhibitors (e.g. ritonavir, nelfinavir, itraconazole).
Simultaneous treatment of solifenacin and a potent CYP3A4 inhibitor is contra−indicated in patients with severe renal impairment or moderate hepatic impairment.
Effect of solifenacin on the pharmacokinetics of other medicinal products: Oral Contraceptives: Intake of Solifenacin showed no pharmacokinetic interaction of solifenacin on combined oral contraceptives (ethinylestradiol/levonorgestrel).
Warfarin: Intake of Solifenacin did not alter the pharmacokinetics of R-warfarin or S-warfarin or their effect on prothrombin time.
Digoxin: Intake of Solifenacin showed no effect on the pharmacokinetics of digoxin.