CONTEXT CONTEXT Empiric antibiotics are often required in hospitalized patients with serious infections who may be septic and at risk for drug resistant organisms. The purpose of this study was to evaluate the observed incidence of acute kidney injury (AKI) in a sample of adult patients receiving either piperacillin-tazobactam and vancomycin or meropenemvancomycin for at least 72 hours. METHODS METHODS Single-center, retrospective matched cohort at a 200-bed Regional Community Medical Center. Adult patients were included in the sample if they were without preexisting renal dysfunction and admitted over an 18-month time period to receive either the combination of piperacillin-tazobactam and vancomycin or meropenem-vancomycin. Sample patients were evaluated for AKI. This condition was defined by the authors as an increase in serum creatinine of 0.5mg/ml or an increase of 50% above baseline during the duration of antibiotic treatment. RESULTS RESULTS A total of 266 patients receiving either combination of antibiotics were evaluated for AKI. The incidence of AKI was significantly higher in the piperacillin-tazobactam and vancomycin group (n = 74/292, 25%) compared with the meropenem-vancomycin group (n=8/74, 9.5%, p=0.008). CONCLUSIONS CONCLUSIONS The results of this study suggest that the combination of piperacillin-tazobactam and vancomycin is associated with an increased incidence of AKI. Higher vancomycin trough concentrations were associated with increased risk for development of AKI.