Comparison of the mathematical equation and trapezoidal approach for 24 h area under the plasma concentration-time curve calculation in patients who received intravenous vancomycin in an acute care setting.

The current recommendation for therapeutic monitoring of vancomycin has recently suggested AUC-guided dosing in patients with serious methicillin-resistant Staphylococcus aureus infections. The study objective was to evaluate mathematical equations and trapezoidal methods for calculating the 24 h area under the plasma vancomycin concentration-time curve (AUC24). The analysis of plasma vancomycin concentrations was performed in 20 adult patients treated with intravenous vancomycin. For each patient, AUC24 was estimated using two methods including, equation and trapezoidal calculation. The AUC24 from two methods was analyzed for correlation. The correlation between the equation and trapezoidal methods was strong. The coefficient of determination (R2 ) values was greater than .99. The two plasma vancomycin concentrations to achieve the highest correlation were concentration at 2.5 to 3 h after starting the infusion and concentration at 1 h before the next dose. Moreover, the AUC24 calculation from trapezoidal and equation methods showed that 19 out of 20 patients (95%) had AUC24 of more than 400 mg·h/L, and more than 50% in this group had AUC24/MIC greater than 600. Of those patients with AUC-trapezoidal >600, 15.38% of patients had trough under 15 mg/L, 15.38% of patients had trough in the range 15 to 20 mg/L and 69.23% of patients had trough more than 20 mg/L. The results of AUC-equation were similar to those of the AUC-trapezoidal method. Our study confirmed that the AUC monitoring is more appropriate than the trough vancomycin concentration. Given these considerations, the AUC-equation method is better and more practical to use in part of a point-of-care treatment, especially in the part of the Bayesian program is not available. The best sampling time point of the peak concentration was 0.5-1 h after 2-h infusion.