Pharmacokinetics and pharmacodynamics of intravenous meperidine in neonates and infants

The pharmacokinetics of meperidine (pethidine) was studied in 21 infants who received a single intravenous dose of 1 mg/kg after surgery (n = 18) or during mechanical ventilation because of respiratory distress (n = 3). Eleven patients were younger than 1 week old, 10 patients were aged from 3 weeks to 5 months, and five of the patients were premature. The pharmacokinetics of meperidine varied greatly between the subjects, with a median elimination half-life of 10.7 hours (range, 3.3 to 59.4 hours), median clearance of 8.0 ml/kg/min (range, 1.8 to 34.9 ml/kg/min), median volume of the central compartment of 2.4 L/kg (range, 0.5 to 4.8 L/kg), and median steady-state volume of distribution 7.2 L/kg (range, 3.3 to 11.0). The great interindividual variability in meperidine pharmacokinetics should be taken into consideration when meperidine is administered to neonates. Although no life-threatening or serious side effects were observed in this study, appropriate care should be exercised when prescribing meperidine for this age group.