METHODS: A pooled population-pharmacokinetic model was built in NONMEM based on data from 14 different studies in different patient populations. Steady-state exposure was simulated and compared across patient subgroups for two US Food and Drug Administration/European Medicines Agency-approved drug labels and optimised doses were derived.
RESULTS: The final model uses postmenstrual age, weight and serum creatinine as covariates. A 35-year-old, 70-kg patient with a serum creatinine level of 0.83 mg dL-1 (73.4 µmol L-1) has a V1, V2, CL and Q2 of 42.9 L, 41.7 L, 4.10 L h-1 and 3.22 L h-1. Clearance matures with age, reaching 50% of the maximal value (5.31 L h-1 70 kg-1) at 46.4 weeks postmenstrual age then declines with age to 50% at 61.6 years. Current dosing guidelines failed to achieve satisfactory steady-state exposure across patient subgroups. After optimisation, increased doses for the Food and Drug Administration label achieve consistent target attainment with minimal (± 20%) risk of under- and over-dosing across patient subgroups.
CONCLUSIONS: A population model was developed that is useful for further development of age and kidney function-stratified dosing regimens of vancomycin and for individualisation of treatment through therapeutic drug monitoring and Bayesian forecasting.
METHODS: We performed a prospective, observational, multi-national, pharmacokinetic study in 29 intensive care units from 14 countries. We collected demographic, clinical and RRT data. We measured trough antibiotic concentrations of meropenem, piperacillin-tazobactam and vancomycin and related them to high and low target trough concentrations.
RESULTS: We studied 381 patients and obtained 508 trough antibiotic concentrations. There was wide variability (4-8 fold) in antibiotic dosing regimens; RRT prescription, and estimated endogenous renal function. The overall median estimated total renal clearance (eTRCL) was 50 mL/min (interquartile range [IQR] 35-65) and higher eTRCL was associated with lower trough concentrations for all antibiotics (p<0.05). The median (IQR) trough concentration for meropenem was 12.1 mg/L (7.9-18.8), piperacillin 78.6 mg/L (49.5-127.3), tazobactam 9.5 mg/L (6.3-14.2) and vancomycin 14.3 mg/L (11.6-21.8). Trough concentrations failed to meet optimal higher limits in 26%, 36%, 72%, and optimal lower limits in 4%, 4%, and 55% of patients for meropenem, piperacillin and vancomycin respectively.
CONCLUSIONS: In critically ill patients treated with RRT, antibiotic dosing regimens, RRT prescription and eTRCL varied markedly and resulted in highly variable antibiotic concentrations that failed to meet therapeutic targets in many patients.