Evaluation of continuous ampicillin/sulbactam infusion in critically ill patients.

Abstract

Medical records of all patients admitted to ICU between January 2019 and December 2020 were retrospectively reviewed. Each patient received a 2/1 g ampicillin/sulbactam loading dose, followed by a continuous infusion of 8/4 g per 24 h. Ampicillin serum concentrations were measured. Main outcomes were reaching of plasma concentrations breakpoint defined by minimum inhibitory concentration (MIC at 8 ml/l) and 4-fold MIC (MIC at 32 ml/l) during steady state of CI. In 50 patients a total of 60 concentration measurements were performed. The first concentration was measured after a median of 29 h (IQR 21-61 h). Mean ampicillin concentration was 62.6 ± 39.1 mg/l. Furthermore, serum concentrations exceeded the defined MIC breakpoint in all measurements (100 %) and were above the 4-fold MIC in 43 analyses (71.1 %). However, patients suffering from acute kidney injury exhibited significant higher serum concentrations (81.1 ± 37.7 mg/l vs. 38.2 ± 24.8 mg/l; p < 0.001). Also, there was a negative correlation between ampicillin serum concentrations and GFR (r = -0.659; p < 0.001). The described dosing regimen for ampicillin/sulbactam is safe with respect to the defined MIC breakpoints for ampicillin, and continuous subtherapeutic concentration is unlikely. However, with impaired renal function drug accumulation occurs, and with increased renal clearance, drug levels can be below the 4-fold MIC breakpoint.