BJA Advance Access published online on October 26, 2007
British Journal of Anaesthesia, doi:10.1093/bja/aem294
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Inter-individual variability in propofol pharmacokinetics in preterm and term neonates
1 Neonatal Intensive Care Unit, Division of Woman and Child
2 Center for Clinical Pharmacology, University Hospital Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium
3 Department of Paediatric Surgery, Erasmus MC—Sophia Children’s Hospital, Rotterdam, The Netherlands
4 Department of Clinical Pharmacy, St Antonius Hospital, PO Box 2500, 3430 EM Nieuwegein, The Netherlands
5 Division of Pharmacology, Leiden/Amsterdam Centre for Drug Research, Leiden University, The Netherlands
* Corresponding author. E-mail: karel.allegaert{at}uz.kuleuven.ac.be
Background: To document covariates which contribute to inter-individual variability in propofol pharmacokinetics in preterm and term neonates.
Methods: Population pharmacokinetics were estimated (non-linear mixed effect modelling) based on the arterial blood samples collected in (pre)term neonates after i.v. bolus administration of propofol (3 mg kg–1, 10 s). Covariate analysis included postmenstrual age (PMA), postnatal age (PNA), gestational age, weight, and serum creatinine.
Results: Two hundred and thirty-five arterial concentration–time points were collected in 25 neonates. Median weight was 2930 (range 680–4030) g, PMA 38 (27–43) weeks, and PNA 8 (1–25) days. In a three-compartment model, PMA was the most predictive covariate for clearance (P<0.001) when parameterized as [CLstd·(PMA/38)11.5]. Standardized propofol clearance (CLstd) at 38 weeks PMA was 0.029 litre min–1. The addition of a fixed value in neonates with a PNA of 
10 days further improved the model (P<0.001) and resulted in the equation [CLstd·(PMA/38)11.5 +0.03] for neonates 10 days. Values for central volume (1.32 litre), peripheral volume 1 (15.4 litre), and peripheral volume 2 (1.29 litre) were not significantly influenced by any of the covariates (P>0.001).
Conclusions: PMA and PNA contribute to the inter-individual variability of propofol clearance with very fast maturation of clearance in neonatal life. This implicates that preterm neonates and neonates in the first week of postnatal life are at an increased risk for accumulation during either intermittent bolus or continuous administration of propofol.
Keywords: anaesthetics i.v., propofol; neonates; pharmacology; sedation
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