AUTOMATED HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ASSAY FOR LESOPITRON, A NOVEL ANXIOLYTIC, IN HUMAN PLASMA USING ONLINE SOLID-PHASE EXTRACTION

A totally automated liquid chromatographic assay method based on a Prospekt solid-phase extraction unit was developed for the analysis of lesopitron and its metabolite 5-hydroxylesopitron in human plasma. On-line solid-phase extraction of lesopitron, 5-hydroxylesopitron and its internal standard in human plasma was carried out using C-2 cartridges. After washing, the test substances were eluted with mobile phase onto an ODS-2 Inertsil column and measured by fluorescence detection. The total time for one analysis was 25 min. The method developed was selective and linear in the concentration range from 1 to 40 ng/ml for both parent drug and metabolite. Recovery of lesopitron and 5-hydroxylesopitron were higher than 80% and the quantification limits were 1 ng/ml for both compounds. Coefficients of variation obtained for precision parameters were all below 14.5% and 13.9% for parent drug and metabolite, respectively. Good values of accuracy were also obtained.