Pharmacokinetics of paracetamol in the neonate and infant after administration of propacetamol chlorhydrate.

The pharmacokinetic parameters of paracetamol were studied after 15 min intravenous infusion of 15 mg/kg of propacetamol (Prodafalgan) in 5 neonates aged less than 10 days and 7 infants aged between 1 and 12 months. Blood was sampled at 0, 0.5, 2 and 6 h after the first intravenous infusion of propacetamol. The infants aged less than 10 days had higher plasma concentrations of paracetamol, a longer half-life (3.5 vs. 2.1 h) and a lower plasma clearance (0.149 vs. 0.365 l/h/kg) than the older children. Dose simulations were performed on the basis of individual data of each child in order to obtain steady-state plasma concentrations between 4 and 18 mg/l permitting the best antipyretic effect for each child. In infants aged less than 10 days a 15 mg/kg dose of propacetamol four times a day (i.e. 30 mg/kg/day paracetamol) is sufficient, corresponding to the dosage recommended by the French pharmacopoeia. On the other hand, double the dosage, nearer to the American dosage, is necessary for children aged over 10 days.