ABSTRACT: Our objective was to develop a population pharmacokinetic (PK) model in order to evaluate the currently recommended dosing regimen in term and preterm neonates. By using an optimal design approach, a prospective PK study was designed and implemented in 60 neonates with postmenstrual ages (PMA) of 26 to 43 weeks. A loading dose of 16?mg/kg was administered at day 1, followed by a maintenance dose of 8?mg/kg daily. Plasma concentrations were quantified by high-pressure liquid chromatography-mass spectrometry. Population PK (popPK) analysis was performed using NONMEM software. Monte-Carlo (MC) simulations were performed to evaluate currently recommended dosing based on a pharmacodynamic index of area under the concentration-time curve (AUC)/MIC?ratio of ?400. A two-compartment model with linear elimination best described the data by the following equations: clearance (CL) = 0.0227 × (weight [wt]/1,765)0.75 × (estimated creatinine clearance [eCRCL]/22)0.672, central compartment volume of distribution (V1) = 0.283 (wt/1,765), intercompartmental clearance (Q) = 0.151 (wt/1,765)0.75, and peripheral compartment volume (V2) = 0.541 (wt/1,765). The interindividual variability estimates for CL, V1, and V2 were 36.5%, 45.7%, and 51.4%, respectively. Current weight (wt) and estimated creatinine clearance (eCRCL) significantly explained the observed variability. MC simulation demonstrated that, with the current dosing regimen, an AUC/MIC?ratio of ?400 was reached by only 68.5% of neonates with wt of <1 kg when the MIC?was equal to?1 mg/kg, versus 82.2%, 89.7%, and 92.7% of neonates with wt of 1 to <2, 2 to <3, or ?3?kg, respectively. Augmentation of a maintenance dose up to 10 or 11?mg/kg for preterm neonates with wt of 1 to <2 or <1?kg, respectively, increases the probability of reaching the therapeutic target; the recommended doses seem to be adequate for neonates with wt of ?2?kg. Teicoplanin PK are variable in neonates, with wt and eCRCL having the most significant impact. Neonates with wt of?<2 kg need higher doses, especially for Staphylococcus spp. with an MIC?value of ?1 mg/liter.
