Pharmacokinetics of cisapride in the horse

The purpose of this study was to determine the pharmacokinetics and absolut e bioavailability of cisapride after intravenous (i.v.) and intragastric (i .g.) administration in healthy, adult horses. Five animals received single doses of 0.1 mg/kg, 0.2 mg/kg and 0.4 mg/kg cisapride by the i.g, route in an open, randomized fashion on different occasions separated by a washout p eriod of at least 48 h. Four of these horses were also given a single i.v. dose of 0.1 mg/kg cisapride. Jugular venous blood was collected periodicall y up to 24 h after dosing. Plasma cisapride concentrations were measured by high-performance liquid chromatography. There was considerable inter individual variability in pharmacokinetic para meters. The mean (SD) values for systemic clearance (Cl) and steady-state v olume of distribution (Vss) were 494 (43.6) mL/h/kg and 1471 (578) mL/kg, r espectively. Although the rate of cisapride absorption was quite rapid, onl y about half the i.g, dose was absorbed systemically. The average terminal half-life (t(1/2)) calculated over three i.g, doses was 2.06 h and that for i.v. administration was 2.12 h. The pharmacokinetics of cisapride from 0.1 mg/kg to 0.4 mg/kg were independent of the i.g. dose.