AUC/MIC-Guided Vancomycin Dosing in Patients With MRSA Bacteremia Results in Decreased Troughs

Vancomycin dosing has remained a controversial topic in the management of infectious diseases as many medical centers move away from trough-guided and toward area under the curve/minimum inhibitory concentration (AUC/MIC)-guided dosing.

Investigators at Boston Medical Center, a large academic facility, implemented a change to their primary targets for vancomycin dosing in January 2018 for patients with methicillin-resistant Staphylococcus aureus (MRSA) blood stream infections (BSI). The goal was to move from troughs to AUC/MIC to reduce the cumulative exposure of vancomycin by 10% and decrease average troughs by 20%.

Matthew Girgis, PharmD, PGY-2 Pharmacy Resident at Boston Medical Center and an investigator on the study, shared the outcomes at the 22^nd annual Making a Difference in Infectious Diseases (MAD-ID 2019) meeting (see video).

The study, part of a quality improvement project rolled out in plan-do-study-act (PDSA) cycles, included a baseline group of patients with MRSA BSI who had been admitted to Boston Medical Center between January and December 2017 and received at least 4 doses of vancomycin. Troughs of 15 to 20 mcg/mL were the primary target. PDSA cycle 1 included patients with MRSA BSI admitted from January to September 2018 and dosed via AUC/MIC. PDSA cycle 2 included patients with MRSA BSI admitted from October to December 2018, dosed via AUC/MIC, and who received empiric dosing and had modifications to documentation requirements.

In the baseline group of 37 patients, the average daily vancomycin dose was 2.9 g and the average trough was 16 mcg/mL (19% supratherapeutic). The incidence of vancomycin-induced nephrotoxicity (VIN) was 8%. In the 36 patients in PDSA cycle 1, the average daily vancomycin dose was 2.5 g and the average trough was 14 mcg/mL (9% supratherapeutic). The incidence of VIN was 19%. In the 13 patients included in PDSA cycle 2, the average daily vancomycin dose was 2.1 g and the average trough was 13.2 mcg/mL (8% supratherapeutic). The VIN incidence was 15%.

Investigators concluded that in patients with MRSA bacteremia, implementing AUC/MIC-guided vancomycin dosing resulted in decreased average troughs and a decrease in daily vancomycin dose administered.

“The increased rate of acute kidney injury seen in the AUC group occurred in the setting of more frequent co-administration of nephrotoxic medications and was not thought to be related to the vancomycin dosing,” the investigators wrote.

The study, “Hospital Wide Implementation of Vancomycin Area Under the Curve/Minimum Inhibitory Concentration (AUC/MIC) Dosing at a Large Academic Medical Center,” was presented at MAD-ID 2019, held May 8-11, 2019, in Orlando, Florida.