The pharmacokinetics of intravenous paracetamol in neonates: size matters most
- 1Neonatal Intensive Care Unit, University Hospitals Leuven, Leuven, Belgium
- 2Department of Paediatric Anaesthesia and Pain Management, Royal Children's Hospital, Melbourne, Victoria, Australia
- 3Department of Anaesthesiology, University of Auckland, Auckland, New Zealand
- Correspondence to Karel Allegaert, Neonatal Intensive Care Unit, University Hospital, Herestraat 49, 3000 Leuven, Belgium;
- Accepted 10 January 2011
- Published Online First 13 February 2011
Background The aim was to describe intravenous paracetamol pharmacokinetics, determine major covariates and suggest a dosing regimen for (pre)term neonates.
Methods A population pharmacokinetic analysis of 943 paracetamol observations from 158 neonates (27–45 weeks' postmenstrual age (PMA)) was undertaken using non-linear mixed effects models. Data from three published studies were pooled with newly collected time–concentration points during repeated intravenous paracetamol administration.
Results A two-compartment (central, peripheral) linear disposition model was used. Population parameter estimates (between-subject variability, %) were central volume 51.9 l/70 kg (21.6%), peripheral volume of distribution 22.7 l/70 kg, clearance 5 l/h/70 kg (40%) and intercompartment clearance 16.2 l/h/70 kg. Covariate information predicts 60.9% of clearance variance. Weight was used to predict patient size and was the major covariate contributing 57.5% of variance. Clearance expressed as mg/kg/h increases only slightly with PMA (0.138 l/kg/h at 28 weeks' PMA to 0.167 l/kg/h at 44 weeks' PMA) and contributes only 2.2% of variance. High unconjugated bilirubin levels contributed an additional 1.2%.
Conclusions Patient size (predicted by weight) is the major covariate of clearance variance in neonates. Using these estimates, a mean paracetamol serum concentration of 11 mg/l is predicted in neonates of 32–44 weeks' PMA given a standard dose of intravenous paracetamol of 10 mg/kg every 6 h. Safety data for this drug are limited in neonates. Continued surveillance therefore remains essential.
Competing interests None.
Ethics approval This study was conducted with the approval of the reanalysis of three already published studies. New data set (PARANEO study): approval by the Local Ethics Committee University Hospitals, Leuven, Belgium.
Provenance and peer review Not commissioned; externally peer reviewed.