Title: Vancomycin area under the curve/minimum inhibitory concentration and corresponding troughs in an ICU
Introduction: Based on the 2020 IDSA vancomycin guidelines, the optimal pharmacodynamic parameter for measuring the efficacy of vancomycin is the area under the curve, with a recommended area under the curve (AUC)/minimum inhibitory concentration (MIC) ratio of 400 to 600 mg·h/L. In this study, the objective was to assess if the vancomycin doses at TidalHealth were adequate to treat suspected or definitive, serious methicillin-resistant Staphylococcus aureus (MRSA) infections while minimizing potential nephrotoxicity.
Methods: Retrospective chart analysis included adult patients ≥ 18 years of age, located in the intensive care unit, with suspected or documented serious MRSA infections with vancomycin trough concentrations achieved at steady-state. Data were collected from January 2017 to December 2019. Area under the curve (AUC) values were calculated using a one-compartment PK equation, and the minimum inhibitory concentration (MIC) was assumed to be 1 mg/L. Nephrotoxicity was defined using the 2012 KDIGO guidelines on acute kidney injury. The primary outcome was the percentage of vancomycin doses in the target AUC range of 400 – 600 mg·h/L.
Results: A total of 68 patients were assessed. There were 19 documented cases of MRSA, and the primary indication treated was for pneumonia (n=48). Only 33 (48.53%) of 68 AUC/MIC values were within the therapeutic range. A total of one patient who was not administered additional nephrotoxic medications developed nephrotoxicity while receiving vancomycin therapy.
Conclusion: Compared with a trough concentration-based dosing strategy, AUC/MIC-based dosing using one-compartment pharmacokinetics exhibited therapeutic concentrations at levels that previously would have been considered subtherapeutic. This approach, however, should be directly compared with AUC-base dosing using two-compartment PK kinetics or Bayesian software.