The pharmacokinetics of droperidol in anesthetized children.

Despite the wide use of droperidol to reduce nausea and vomiting in children, its pharmacokinetics have not been described in pediatric patients. Twelve ASA Class I-II children, undergoing tonsillectomy and adenoidectomy, received standardized anesthesia; none of the children received premedication. After induction of general anesthesia, droperidol (0.05 mg/kg) was injected intravenously as a bolus. Droperidol plasma concentrations were determined by radioimmunoassay. Pharmacokinetic data were analyzed by model-independent methods. The pharmacokinetic parameters (mean +/- SD) for the studied population were elimination half-life: 101.5 +/- 26.4 min, mean residence time: 127.2 +/- 28.6 min, volume of distribution at steady state: 0.58 +/- 0.29 L/kg and clearance: 4.66 +/- 2.28 mL.kg-1 x min-1. The clearance and volume of distribution at steady state values are lower than those reported for the adult population, and they apparently decreased in a parallel fashion. The smaller volume of distribution at steady state is consistent with the lipophilic distribution of droperidol and the reduced content of adipose tissue in children. The elimination half-time and mean residence time values are similar to those reported previously for adults. The relatively short half-life of droperidol for our pediatric population does not explain its extended antiemetic action. It does, however, reaffirm that the pharmacokinetic duration of a drug's action is only one of the determinants of its clinical duration.