Pharmacokinetics of phenoperidine in anaesthetized patients undergoing general surgery

The pharmacokinetics of phenoperidine have been studied in five anaesthetized patients receiving a 2-mg bolus dose i.v. Plasma concentrations were measured using a sensitive radioimmunoassay method. The distribution of phenoperidine was described according to a two-compartment open model. The mean distribution half-life (T1/2 alpha) for the five patients was short (2.2 min); the mean elimination half-life (T1/2 beta) was 193 min. The mean whole body clearance was 22 ml min-1 kg-1 and the apparent steady state distribution volume (VSS) was 5.7 litre kg-1. Secondary concentration peaks occurred in all patients; in two patients these were substantial and occurred 80 min after injection.