(637) Use of Therapeutic Drug Monitoring to Optimize Meropenem Dosing in Hospitalized Patients

Introduction: Previous studies have shown that conventional meropenem dosing regimens may lead to unacceptable pharmacokinetic/pharmacodynamic (PK/PD) target attainment in critically ill patients. The objectives of this study were to evaluate the PK/PD target attainment of meropenem using standard dosing regimens and to further assess clinical and microbiological outcomes.

Methods: We conducted a single-center, retrospective review between Jan-Dec 2022, of adult patients receiving meropenem with serum concentrations obtained at steady state. PK/PD targets assessed in this study were free drug concentration maintained above the MIC of the pathogen (100% fT>MIC) or 4-fold higher than the MIC of the pathogen (100% fT≥4xMIC) throughout the dosing interval. Clinical success was defined as resolution of presenting signs and symptoms of infection and no need for further antibacterial therapy. Microbiological success was defined as absence of the pathogen in repeat cultures.

Results: Sixty-seven patients were included in the analysis. This is a preliminary analysis of 32 patients of this cohort. The median age was 56.5 (IQR, 40.5-66.5). The most common source of infection was pneumonia (41%), and most patients had an ICU admission (75%). The median serum creatinine on the day meropenem concentrations was 0.85 mg/dL (IQR 0.62-1.32). The median meropenem daily dose was 3g (IQR, 3-6). Eighty-seven percent (n=28) of patients were on an intermittent infusion. Eighty-four percent of patients (n=27) achieved 100% fT>MIC and 53% (n=17) achieved 100% fT≥4xMIC. Dose adjustments to optimize PK/PD were performed in 62% (n=20) of patients. The most common dose adjustment was a decrease in total daily dose (55%, n=11/20), occurring most often in patients with a PK/PD target of 100% fT≥4xMIC (n=9). Clinical success was achieved in 75% of patients (n=24) and microbiological success was achieved in 81% (n=26).

Conclusions: In this preliminary analysis, most patients attained 100% fT>MIC. Of note, the higher PK/PD target of 100% fT≥4xMIC was achieved in over 50% with about half of these patients requiring a decrease in the meropenem daily dose. The ability to obtain meropenem concentrations provided the opportunity to optimize meropenem exposure in 62% of patients.