Pharmacokinetics and Pharmacodynamics of Continuous Infusion Meropenem in Overweight, Obese, and Morbidly Obese Patients with Stable and Unstable Kidney Function: A Step Toward Dose Optimization for the Treatment of Severe Gram-Negative Bacterial Infections

Background: Meropenem is an anti-Gram-negative antimicrobial, the time-dependent activity of which may be maximized through administration by continuous infusion. Objectives: The objectives of this study were to characterize the pharmacokinetics of continuous infusion meropenem in relation to body size and Cockcroft–Gault estimated creatinine clearance (CLCR) in overweight and obese patients with stable and unstable kidney function with the intent of creating a nomogram for optimal dosing. Patients and Methods: Patients from a single institution with a body mass index ≥25 kg/m2 receiving meropenem by continuous infusion with measurement of meropenem steady-state concentrations (Css) were identified. Individual Bayesian estimates of meropenem volume of distribution of the central compartment (Vc) and clearance (CL) were calculated and relationships to body size descriptors and CLCR estimated using these body size descriptors were defined by regression. Kidney function stability was defined based on median absolute deviation, stratification by the ratio of maximum to minimum serum creatinine (SCr) and individual patient-level regression of SCr over time. The influence of kidney function stability on meropenem CL estimation by CLCR was tested. Results: A total of 375 patients (77.9 % male) with 846 Css values (62.4 % of patients with ≥2 measurements) were identified. The median daily dose of meropenem and frequency of infusion bag changes were 2000 mg/day and four times per day, respectively. The meropenem Css values were ≥16, ≥8, ≥4, and ≥2 mg/L for 41.1, 76.1, 97.4, and 99.9 % of observations, respectively. The median (range) age, weight, and BMI were 66 (24–90) years, 90 (70–250) kg, and 30.8 (25.1–81.6) kg/m2, respectively. The mean [standard deviation (SD)] serum creatinine at baseline was 1.57 (1.37) mg/dL. The mean (SD) Vc was 28.1 (1.36) L and not related to body size, while CL was 8.85 (6.40) L/h and best related to CLCR estimated using adjusted body weight (ABW). The meropenem CL to CLCR relationship was not significantly impacted by the presence or absence of kidney function stability. The user-friendly dosing nomogram based on CLCR estimated using ABW showed that optimal drug exposure [Css ≥ minimum inhibitory concentration (MIC)] may be obtained even against multi-drug resistant (MDR) pathogens when considering dosages up to 1250 mg every 6 h by continuous infusion. Conclusions: Meropenem CL is best estimated using CLCR with ABW in patients with a BMI ≥25 kg/m2 and this relationship is not altered by unstable kidney function. Application of our dosing nomogram may improve the care of overweight and obese patients with severe MDR Gram-negative infections treated with meropenem by continuous infusion.