Imipenem Population Pharmacokinetics: Therapeutic Drug Monitoring Data Collected in Critically Ill Patients with or without Extracorporeal Membrane Oxygenation

Abstract

Carbapenem pharmacokinetic profiles are significantly changed in critically ill patients because of the drastic variability of the patients' physiological parameters. Published population PK studies have mainly focused on specific diseases and the majority of these studies had small sample sizes. The aim of this study was to develop a population PK model of imipenem in critically ill patients that estimated the influence of various clinical and biological covariates and the use of Extracorporeal Membrane Oxygenation (ECMO) and Continuous Renal Replacement Therapy (CRRT). A two-compartment population PK model with Creatinine clearance (CrCL), body weight (WT), and ECMO as fixed effects was developed using the non-linear mixed effect model (NONMEM). A Monte Carlo simulation was performed to evaluate various dosing schemes and different levels of covariates based on the pharmacokinetic/pharmacodynamic index (ƒ%T>MIC) for the range of clinically relevant minimum inhibitory concentrations(MICs). The results showed that there may be insufficient drug use in the clinical routine drug dose regimen, and 750mg Q6h could achieve a higher treatment success rate. The blood concentrations of imipenem in ECMO patients were lower than that of non-ECMO patients, therefore dosage may need to be increased. The dosage may need adjustment for patients with CrCL ≤ 70ml/min, but dose should be lowered carefully to avoid the insufficient drug exposure. Dose adjustment is not necessary for patients within the WT ranging from 50-80 kg. Due to the large variation in PK profile of imipenem in critically ill patients, TDM should be carried out to optimize drug regimens.