192 - The Use of Area Under the Curve to Determine Therapeutic Vancomycin Dosing in Skin and Soft Tissue Infections

Background: The vancomycin AUC/MIC target ratio of 400 to 600 mg*h/L that is recommended (level IA+) in the 2020 IDSA/ASHP vancomycin TDM guidelines is appropriate for patients with complicated MRSA infections; using lower targets for less complicated infections may reduce the risk for nephrotoxicity without compromising efficacy. The current methodology surrounding vancomycin AUC/MIC targets is unrefined, with no source specific targets identified, especially for relatively lower risk MRSA infections such as skin and soft tissue infections (SSTIs).

Methods: This was a retrospective observational study of hospitalized patients at the Veterans Affairs Health Care System in San Diego, CA with a SSTI and prescribed intravenous vancomycin between January 1, 2016 and December 31, 2019. Patients included were adults, 18 years of age and older, treated with IV vancomycin with ≥1 measured concentration for at least one of the ICD-10 CM codes for SSTI. Patients were excluded if they had any of the following SSTIs: (1) osteomyelitis; (2) infection related to chronic ulcers or wounds; (3) head SSTI; (4) peri-rectal SSTI; (5) human or animal bite SSTI; (6) SSTI related to retained foreign body; (7) necrotizing SSTI; (8) surgical site infection. Patients were also excluded if they were undergoing dialysis or had severe immunosuppression. 

Results: A total of 722 patients on vancomycin for a SSTI were identified from the database query for screening, and 243 (34%) met inclusion criteria for the study. Classification and Regression Tree (CART) modeling identified a calculated AUC of >253 as having the highest correlation with clinical success. Clinical cure was significantly different between the AUC ≤253 (6/9 [67%]) and AUC >253 (214/234 [91%]) cohorts (p=0.043). There were no differences in hospital length of stay or duration of vancomycin therapy. Nephrotoxicity occurred in seven patients, all of who had AUC >253.

Conclusion: Overall treatment success in patients with SSTIs was associated with a vancomycin AUC >253, which is lower than the guideline recommended range of 400-600. Identification of vancomycin AUC targets for other low risk sources of infection, such as UTIs, is needed to prevent vancomycin overexposure.