PI-107 - OPTIMIZING VANCOMYCIN DOSING REGIMENS FOR OBESE PATIENTS

S. Lim¹, H. Lee², S. Baek³, S. Yoon³, J. Chung³; ¹Seoul National University, Seongnam-si, Republic of Korea, ²Department of Clinical Pharmacology and Therapeutics, Seoul National University College of Medicine and Bundang Hospital, Seongnam-si, Kyonggi-do, Republic of Korea, ³Seoul National University Bundang Hospital, Seongnam-si, Republic of Korea.

Background: Vancomycin is a glycopeptide antibiotic effective against Gram-positive bacteria, and therapeutic drug monitoring (TDM) is recommended due to its narrow therapeutic range. Prior research has shown that vancomycin accumulates to higher levels in the body within 10 days of the initial dose in obese patients compared to non-obese patients. While guidelines provide vancomycin loading and maintenance doses for general patients, obese patients are only given guidelines for the loading dose, and no specific guidelines for the maintenance dose are provided. Therefore, it is necessary to develop dosing guidelines to ensure the efficacy and safety of vancomycin in obese patients.

Methods: The retrospective cohort study included adults with eGFR-CKD-EPI ≥ 60 mL/min/1.73 m², who underwent vancomycin TDM at Seoul National University Bundang Hospital from 2021 to July 2024. Obese was defined as a body mass index (BMI) ≥ 30 kg/m², and subjects were classified into underweight, normal, overweight, and obese categories. The proportion of patients with vancomycin area under the curve (AUC) ≥ 600 mg*h/L was compared in obese and non-obese patients. Multiple linear regression was conducted to identify covariates affecting vancomycin clearance (CL). A novel dosing regimen was devised based on the most significant covariates identified by multiple regression. The AUC predicted by the novel dosing regimen was then compared to the AUC estimated by the dosing regimen used in the actual patient.

Results: A total of 731 patients were included. A significant difference in the proportion of AUC ≥ 600 mg*h/L was observed between the obese and non-obese (p = 0.0024). Multiple regression analysis showed a significant correlation between lean body mass (LBM) and CL in the obese patients (p = 0.023). In the obese, the mean predicted AUC for the total body weight (TBW)-based regimen and the LBM-based regimen were 711.1 (95% CI: 708.19-927.62) and 547.7 (95% CI: 462.62-588.77), respectively, with a statistically significant difference (p < 0.001).

Conclusion: In obese patients, the proportion of AUC ≥ 600 mg*h/L was significantly lower when the LBM-based dosing regimen was used compared to the TBW-based dosing regimen. These results suggest that current vancomycin dosing guidelines for obese patients may need to be revised to reflect LBM-based dosing.