Vancomycin area under the curve/minimum inhibitory concentration and trough level concordance–evaluation on an urban health unit

BACKGROUND: A vancomycin AUC/MIC (area under the curve/minimum inhibitory concentration) of 400–600 mg•h/L is associated with improved clinical outcomes for the treatment of methicillin resistant Staphylococcus aureus (MRSA) infections. Currently, there are still limited studies evaluating the relationship between vancomycin trough and AUC. OBJECTIVES: To evaluate the correlation between vancomycin trough and AUC/MIC and determine if trough-guided monitoring is an adequate predictor of AUC/MIC in the Urban Health population at St Paul’s Hospital. METHODS: This was a retrospective chart review of 29 patients from November 2019 to February 2021. Patient demographics and laboratory data were collected from electronic medical records. The two-level equation-based approach was used to calculate AUC/MIC. The proportion of AUC/MIC values within target (400–600 mg•h/L) despite subtherapeutic troughs, and the proportion of AUC/MIC values supratherapeutic when trough is within target (15–20 mg/L) were the primary endpoints. MAIN RESULTS: Fifty-seven sets of levels were collected and 75% of vancomycin troughs and AUC(24) were found to be discordant. When trough was 10–14.9 mg/L, AUC(24) was > 400 mg•h/L in 94% of cases and when trough was 15–20 mg/L, AUC(24) was > 600 mg•h/L in 69% of cases. There was a moderate correlation between vancomycin trough and AUC(24h) (R(2) = 0.57; p < 0.001). CONCLUSION: A vancomycin trough between 15 and 20 mg/L may result in an AUC/MIC greater than necessary for clinical efficacy. Considering these findings and the practical concerns of AUC-guided monitoring, a modest reduction in target troughs to prevent vancomycin toxicity warrants clinical consideration and further evaluation.