Vancomycin is widely used to treat severe infections caused by resistant Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA). Due to its narrow therapeutic window and high risk of nephrotoxicity, its safe use requires rigorous therapeutic drug monitoring (TDM). Although current recommendations favor estimating the area under the concentration–time curve over the minimum inhibitory concentration (AUC/MIC) as a more precise parameter, many institutions still rely solely on trough levels (Cmin), which can hinder dose individualization.

This retrospective study analyzed vancomycin monitoring practices in a medium-sized hospital in southern Brazil between October 2023 and October 2024. Thirty-three adult inpatients treated with vancomycin were included, divided into four groups: HDV (hemodialysis with TDM), HDNV (hemodialysis without TDM), NDV (non-dialysis with TDM), and NDNV (non-dialysis without TDM). Serum levels were classified as subtherapeutic (<15 mg/L), therapeutic (15–20 mg/L), or supratherapeutic (> 20 mg/L).

Among the 19 patients monitored, supratherapeutic concentrations predominated, with an overall mean of 29.6 mg/L. In the HDV group, all patients had initial levels above 20 mg/L (mean = 33.7 mg/L), and only three reached the therapeutic range during treatment. In the NDV group, variability was higher: three patients started within range, two below, and four above; only four achieved target levels during hospitalization. The analysis revealed that monitoring alone was insufficient to ensure adequate drug exposure. The lack of effective dose adjustment, particularly in dialysis patients, suggests reliance on fixed dosing regimens without considering individual pharmacokinetic factors. Laboratory data also appeared not fully integrated into clinical decision-making, limiting the overall impact of TDM.

Vancomycin monitoring practices were inadequate to achieve safe therapeutic levels in most patients. Implementation of AUC/MIC-based protocols, supported by clinical pharmacists and therapeutic decision-support tools, is essential to optimize vancomycin use and minimize risks associated with under or overexposure.