Impact of weight-based dosing on vancomycin dosing and trough levels

Abstract

Background: In 2009, the American Society of Health System Pharmacists (ASHSP), Infectious Diseases Society of America (IDSA) and Society of the Infectious Diseases Pharmacists (SI DP) released a consensus statement on vancomycin dosing and monitoring. The appropriateness of these guidelines for a local population, particularly the subset of obese patients, has not been well-studied. Methods: A retrospective chart review was conducted on patients hospitalized at an acute care, university-affiliated, community hospital who received intravenous vancomycin for suspected/documented infections prior to and after implementation of the 2009 guidelines. Preguidelines, patient received vancomycin, 1 gram every 12 hours. After the guidelines were implemented, patients were dosed on actual body weight (ABW), lS-20mg/kg, or 2S-30mg/kg in seriously ill patients, every 8-12 hours. We compared the frequency of achieving therapeutic troughs, nephrotoxicity and trough group levels stratified by Body Mass Index (BMI). Results: There were no significant differences in achieving therapeutic troughs and nephrotoxicity. But when adjusted for BM I, was a significant difference in proportion of trough levels when between the two groups, p=0.0109. However, a large number of patients in the conventionally-dosed group were excluded due to inconsistent dosing. In the ABW-dosed group, there was a high number of supratherapeutic trough levels in 48% of patients with BMls >3S, p=O.OOS Conclusions: Obese patients may require an alternate dosing strategy as the ABW-dosing based on the 2009 national guidelines resulted in supra-therapeutic levels in patients with high BMls. Implementing guidelines-based monitoring resulted in more consistently and appropriately drawn trough levels.