775. Comparison of Initial Vancomycin Costs and Target Attainment Between Trough- and 24-Hour Area Under the Concentration–Time Curve (AUC24)-Guided Dosing

Abstract

BackgroundVancomycin is the treatment-of-choice for most invasive methicillin-resistant Staphylococcus aureus (MRSA) infections. Although serum trough concentration-guided vancomycin dosing is the current standard, dosing based on AUC24 to minimum inhibitory concentration ratio best predicts efficacy while often reducing trough concentrations associated with increased nephrotoxicity. Data regarding the impact of AUC24-guided dosing on drug costs is sparse. We compared the relative initial acquisition cost of vancomycin when utilizing AUC24- vs. trough-guided dosing. We also sought to describe current dosing practices relative to attainment of targeted vancomycin exposures.MethodsA retrospective, single-center cohort study was performed on 200 randomly-selected hospitalized adults at Duke University Hospital (DUH) in calendar year 2017 with suspected or confirmed invasive MRSA infection and stable renal function. For the primary outcome measure, a cost-minimization analysis was performed utilizing DUH wholesale vancomycin acquisition cost through 48 hours as determined from prescribed trough- and Bayesian computer-simulated AUC24-guided dosing. Descriptive statistics were utilized to characterize dosing, serum concentration monitoring practices and attainment of goal vancomycin exposures.ResultsIn the 200 enrolled subjects, the median (IQR25,75) cost difference per patient among trough- and AUC24-guided dosing was $0.00 (-15.02, 15.02). Serum vancomycin troughs were labeled correctly in 54% of samples, while 20.7% exceeded 2 hours of the next scheduled dose. Mean loading doses were 21.0 mg/kg and 24.8 mg/kg, respectively. Goal steady-state troughs were achieved in 22% of subjects. Initial dosing was predicted to achieve an AUC24 within 400–600 mg.hr/L in 66.5% and 100%, respectively. Troughs ≥15 mg/dL (a known risk factor for nephrotoxicity) were measured in 32.1% of trough-guided dosing regimens while predicted in 5.0% of AUC24-guided dosing regimensConclusionWhen compared with trough-, AUC24-guided dosing may lead to improved attainment of vancomycin target exposures, including potential reductions in excessive and incorrectly labeled trough concentrations, without impacting drug acquisition costs.Disclosures All authors: No reported disclosures.