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 (AUC₂₄) 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. AUC₂₄ 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. AUC₂₄ 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. AUC₂₄ value categorization was compared across the three models and reported as percent agreement.

Results: Overall, 466 AUC₂₄ values were estimated in 188 patients. Overall, 52%, 42%, and 47% of the AUC₂₄ values were therapeutic for the Goti, Colin, and Thomson models, respectively. The agreement of AUC₂₄ 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 AUC₂₄ 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.