DETERMINATION OF BAYX7195, A NOVEL LEUKOTRIENE D-4 ANTAGONIST, IN HUMAN PLASMA BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH POSTCOLUMN PHOTO DERIVATIZATION AND FLUORESCENCE DETECTION

Methods to determine plasma concentrations of the leukotriene D-4 antagonist BAY x 7195 by HPLC with post-column photo derivatisation and fluorescence detection are described. Following dilution and centrifugation plasma supernatant is injected onto the HPLC system allowing the selective determination of the drug with a limit of quantitation (LOQ) of 10 mu g/1 (method A). Sensitivity was further enhanced to a LOQ of 0.6 mu g/1 by employing solid-phase extraction whereby the analyte concentration in the injection solution was increased (method B). Data on recovery, accuracy and precision of both methods throughout the working range are presented. BAY x 7195 is stable in plasma after repeated freeze-thaw cycles and upon storage at -20 degrees C for at least 13 months. Method A was applied to a clinical study with oral administration of 250 mg BAY x 7195 where ca. 1% of the maximum plasma concentrations still could be accurately and precisely quantified. Method B was employed to determine the drug in plasma after administration of 1 mg as aerosol.