Population Pharmacokinetics of Polymyxin B in Obese Patients for Resistant Gram-Negative Infections

Polymyxin B is weight-based dosed, potentially placing obese patients at higher risk of nephrotoxicity, but pharmacokinetic data and dosing recommendations specific to this population were lacking. This study in 26 obese patients (BMI >30) receiving polymyxin B for resistant Gram-negative infections built a population pharmacokinetic model using Phoenix NLME, then used Monte Carlo simulation to compare dosing strategies based on total, ideal, and adjusted body weight. Body weight itself did not significantly affect polymyxin B pharmacokinetics, and adjusted-body-weight-based regimens (with a daily dose under 250 mg) showed the best balance of achieving target exposure while minimizing toxicity risk compared with total- or ideal-body-weight-based dosing. These findings support using adjusted body weight, rather than total body weight, to guide polymyxin B dosing in obese patients.