Estimation of piperacillin clearance with different glomerular filtration rate formulas in critically ill children

Aims Glomerular filtration rate (GFR) is difficult to assess in critically ill children using gold standard method and alternatives are needed. This study aimed to determine the most accurate GFR estimation formula for assessing piperacillin clearance in critically ill children, using a published piperacillin pharmacokinetics (PK) population model. Methods All children hospitalized in the paediatric intensive care unit of a single institution who were receiving piperacillin were included. PK were described using the nonlinear mixed effect modelling software MONOLIX. In the initial PK model, GFR was estimated according to the Schwartz 1976 formula. We evaluated a set of 12 additional validated formulas, developed using plasma creatinine and/or cystatin C concentrations, in the building model to assess the lowest between‐subject variability for piperacillin clearance. Results We included 20 children with a median (range) postnatal age of 1.9 (0.1–19) years, body weight of 12.5 (3.5–69) kg. Estimated GFR according to the Schwartz 1976 formula was 160.5 (38–315) mL min−1 1.73 m−2. Piperacillin clearance was best predicted by the Bouvet combined formula. Conclusion The combined Bouvet formula was the most accurate GFR estimation formula for assessing piperacillin clearance in critically ill children.