Pharmacokinetics
Corey Diamond, PharmD
Therapeutic drug monitoring for vancomycin in serious MRSA infections has increasingly shifted toward area under the curve (AUC)–based approaches, but these methods demand significant labor and suit nonsevere cases poorly. Most hospitalized patients who receive vancomycin do not have confirmed MRSA, highlighting the need for a pragmatic, scalable dosing strategy.
In a study published in the May 2025 issue of Pharmacotherapy, researchers from an eight-hospital system evaluated whether a blended protocol, using AUC monitoring for severe or likely MRSA infections and trough-based dosing for all others, could reduce vancomycin exposure and nephrotoxicity without compromising care. Their retrospective, pre–post cohort analysis showed statistically significant reductions in cumulative vancomycin dosing and AKI, while also demonstrating considerable pharmacist time and cost savings. These findings support selective AUC implementation as a resource-conscious alternative to universal AUC dosing.
Study design
The researchers conducted a quasi-experimental analysis to evaluate a newly implemented vancomycin dosing protocol across a health system in Minnesota and western Wisconsin. In June 2023, the team implemented a guideline that reserved AUC-based dosing (target 400–600 mg*h/L) for patients with suspected or confirmed severe MRSA infections and used trough-based dosing (target 10–15 µg/mL) for all others. Pharmacists tailored the level of monitoring based on patient acuity.
The investigators retrospectively reviewed data from 6 months before and after implementation. They included adult inpatient encounters with at least one dose of I.V. vancomycin, omitting outpatient and ambulatory settings. Chart reviews supplemented electronic data to determine dosing strategy and identify AKI events, defined using KDIGO criteria. Secondary endpoints included length of stay, frequency of vancomycin levels, pharmacist workload, and adherence to the new protocol. A subgroup analysis focused on patients who received four or more doses, reflecting higher cumulative exposure.
To estimate pharmacist time savings, the team applied two published benchmarks: One assuming 3 minutes saved per patient, and the other assuming 7 minutes. They calculated cost savings using a median pharmacist wage.
Results
The study included 8,155 encounters (3,916 pre-implementation and 4,239 postimplementation). After implementing the new protocol, the median cumulative vancomycin dose decreased by 500 mg, a statistically significant reduction. The proportion of patients who underwent vancomycin serum level monitoring also significantly declined. Among patients receiving four or more doses, the rate of AKI dropped from 9.6% to 7.2%, and this reduction reached statistical significance. Likewise, the percentage of serum levels that exceeded 15 µg/mL significantly decreased.
Only 4.5% of reviewed patients had documented severe MRSA infections. The team found that pharmacists followed protocol in nearly 89% of cases, with most deviations involving unnecessary AUC use for nonsevere infections. Trough-based dosing accounted for about one-third of postimplementation encounters. Using that estimate, the researchers calculated that the blended strategy saved between 2,200 and 5,200 minutes of pharmacist time and approximately $2,400 to $5,600 in labor over 6 months. Projected annually, savings could exceed $11,000, not including reductions in laboratory and phlebotomy resource use.
Length of stay and mortality remained similar between the two groups and did not change in a statistically significant manner after adjusting for baseline characteristics.
Takeaways
The authors concluded that implementing a blended vancomycin dosing strategy led to statistically and clinically significant reductions in cumulative dosing, frequency of serum levels, and AKI incidence. Most patients received vancomycin for nonsevere infections, and only a small proportion had confirmed severe MRSA. By incorporating trough-based dosing for lower-risk cases, the protocol saved pharmacist time and partially offset the costs of AUC software. Deviations from the guideline were uncommon and mostly involved unnecessary AUC monitoring, underscoring the need for continued education and protocol reinforcement.
“This study reinforces that clinicians have more than one effective option for managing vancomycin therapy,” said the authors, “When AUC isn’t the right fit, trough-based dosing can step in as a strong alternative.” The authors go on to note that by limiting AUC monitoring to patients with severe MRSA infections and using streamlined approaches for others, institutions can preserve stewardship efforts without overwhelming staff. ■