Determination of phenytoin in human plasma by a validated hplc method: application to therapeutic drug monitoring study

Abstract

The aim of this study was to develop a simple and reliable HPLC method for the determination of phenytoin (PHT) in human plasma. Accuracy (RE%) were determined between (-0.93%) to 2.49% and precision (RSD%) values was ≤7.94. The quantitation limit was 3.54 μg/mL and recovery was found between 82.15% and 101.06%. The method was applied to real plasma samples (n = 7). Plasma-PHT levels were found between 1.12 and 18.76 μg/mL (9.52 ± 7.78, mean±SD). Both the plasma and dose-rated plasma results of PHT showed so high RSD% which were between 81.74% and 89.61%. In addition plasma-PHT levels were outside the recommended treatment range in 4 of the 7 patients (57.14%) examined, and also surprisingly PHT could not be detected in a patient's plasma. This procedure is relatively simple, precise, and applicable for routine therapeutic drug monitorization of PHT in neurology clinics or toxicological analyses in reference laboratories.