Therapeutic drug monitoring of cefepime with micellar electrokinetic capillary chromatography: Assay improvement,quality assurance,and impact on patient drug levels

The improvement and performance of a micellar electrokinetic capillary chromatography assay for cefepime in human serum and plasma with a 50 μm id fused‐silica capillary elongated from 40 to 60 cm is reported. Sample preparation with dodecylsulfate protein precipitation at pH 4.5, the pH 9.1 separation medium, and the applied voltage were as reported previously [16]. The change resulted in a significant lower current, higher resolution, and increased detection time intervals. The performance of the assay with multilevel internal calibration was assessed with calibration and control samples. Quality assurance data of a 2‐year period assessed under the new conditions demonstrated the robustness of the assay. In serum samples of patients who received both cefepime and sulfamethoxazole, cefepime could not be detected due to the inseparability of the two compounds. The presence of an interference can be recognized by an increased peak width (width > 0.2 min), the appearance of a shoulder or an unresolved double peak. The patient data gathered during a 3‐year period reveal that introduction of therapeutic drug monitoring led to a 50% reduction of the median drug level. The data suggest that therapeutic drug monitoring can help to minimize the risk of major adverse reactions and to increase drug safety on an individual basis.