Prediction of Area Under the Curve from Urinary Vancomycin Concentrations Measured Using a Simple Method

Therapeutic drug monitoring (TDM) is recommended during vancomycin (VCM) administration to adjust the dosage such that the area under the curve (AUC) remains between 400 and 600 µg·h/mL (minimum inhibitory concentration = 1 µg/mL). However, measuring the AUC requires frequent blood sampling, which increases the burden of added time and cost for testing on both patients and healthcare personnel. Therefore, we aimed to address these issues by developing a simple and rapid method for measuring urinary VCM levels using solid-phase extraction and fluorescence spectrometry. The developed method had a quantification range of 100-2,000 µg/mL, with an accuracy of 100.0%-108.5% for concentrations of 200, 1,000, and 2,000 µg/mL. The intra- and inter-day relative standard deviations were below 3.39% and 4.48%, respectively. Furthermore, to predict the AUC from urinary VCM concentrations, we calculated the slope of the urinary concentrations at 7-12 h post-VCM administration in six patients. The slope for one patient differed significantly from that for the others, and the AUC was obtained using practical AUC-guided TDM for vancomycin (PAT) ver. 3.0c for the patient whose value deviated from the recommended range. A negative correlation was observed between the slope and AUC, with a correlation coefficient of 0.65, suggesting the potential for predicting AUC from urinary concentration trends. The use of urine samples, which can be easily obtained, for VCM dose adjustment is expected to contribute to providing more appropriate drug therapy to patients and reduce the burden on healthcare professionals.