The pharmacokinetics of tolterodine and the 5-hydroxymethyl metabolite are not influenced by gender. Pharmacokinetic differences due to race have not been established. The pharmacokinetics of tolterodine in patients with renal insufficiency have not been evaluated. The renal excretion of tolterodine and the 5-hydroxymethyl metabolite are negligible, and a decrease in total body clearance is not expected in patients with renal insufficiency. However, patients with renal impairment should be treated with caution.
Liver impairment can significantly alter the disposition of tolterodine.
Fluoxetine is a selective serotonin reuptake inhibitor and a potent inhibitor of cytochrome P450 2D6 activity. Fluoxetine thus alters the pharmacokinetics in patients who would otherwise be extensive metabolizers of tolterodine to resemble the pharmacokinetic profile in poor metabolizers. In healthy volunteers, coadministration of tolterodine 2 mg twice daily for 7 days and a single 25-mg dose of warfarin on day 4 had no effect on prothrombin time, Factor VII suppression , or on the pharmacokinetics of warfarin. These characteristics were well balanced across treatment groups for the three studies.