Bayesian Estimation of Vancomycin Exposure and Population Pharmacokinetics in Obese Patients

Background/Objectives: This study compared the pharmacokinetic (PK)/pharmacodynamic (PD) targets of vancomycin in obese patients using two Bayesian programs to evaluate the accuracy and bias of these estimates. Additionally, population pharmacokinetics in obese patients were compared with those in the general patient population. Methods: Medical records of obese adults [body mass index (BMI) ≥ 30 kg/m²] treated with vancomycin at Ajou University Hospital between 2010 and 2017 were retrospectively reviewed. Patients with peak (C_peak) and trough (C_trough) concentrations were included. Vancomycin area under the plasma concentration-time curve (AUC) and C_trough were estimated using Capcil (ver 6.31) and MwPharm (ver 2.3.1.89) software. Accuracy and bias were analyzed, and population PK parameters were evaluated. Results: A total of 149 cases were analyzed. AUC estimates from one-point sampling using Capcil were significantly lower than the reference values, whereas MwPharm produced estimates closer to the reference with higher accuracy and lower bias. C_trough estimates from one-point sampling showed high accuracy for both programs. Obese patients exhibit lower volume of distribution, higher total body clearance, and shorter elimination half-life than the general patient population. Conclusions: Vancomycin pharmacokinetics differ in obese patients. Bayesian analysis using MwPharm showed AUC and C_trough estimates that were closer to the reference values and exhibited lower bias than those obtained with Capcil in this dataset. These findings may support more informed dosing decisions for vancomycin in obese patients.