Discrepancies Between Bayesian Vancomycin Models Can Affect Clinical Decisions in the Critically Ill

PURPOSE: To assess the agreement in 24-hour area under the curve (AUC(24)) value estimates between commonly used vancomycin population pharmacokinetic models in the critically ill. MATERIALS AND METHODS: Adults admitted to intensive care who received intravenous vancomycin and had a serum vancomycin concentration available were included. AUC(24) values were determined using Tucuxi (revision cd7bd7a8) for dosing intervals with a vancomycin concentration using three models (Goti 2018, Colin 2019, and Thomson 2009) previously evaluated in the critically ill. AUC(24) values were categorized as subtherapeutic (<400 mg·h/L), therapeutic (400–600 mg·h/L), or toxic (>600 mg·h/L), assuming a minimum inhibitory concentration of 1 mg/L. AUC(24) value categorization was compared across the three models and reported as percent agreement. RESULTS: Overall, 466 AUC(24) values were estimated in 188 patients. Overall, 52%, 42%, and 47% of the AUC(24) values were therapeutic for the Goti, Colin, and Thomson models, respectively. The agreement of AUC(24) values between all three models was 48% (223/466), Goti-Colin 59% (193/466), Goti-Thomson 68% (318/466), and Colin-Thomson 67% (314/466). CONCLUSION: In critically ill patients, vancomycin AUC(24) values obtained from different pharmacokinetic models are often discordant, potentially contributing to differences in dosing decisions. This highlights the importance of selecting the optimal model.