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 anta gonist BAY x 7195 by HPLC with post-column photo derivatisation and fl uorescence detection are described. Following dilution and centrifugat ion plasma supernatant is injected onto the HPLC system allowing the s elective 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 con centration in the injection solution was increased (method B). Data on recovery, accuracy and precision of both methods throughout the worki ng 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 m onths. Method A was applied to a clinical study with oral administrati on of 250 mg BAY x 7195 where ca. 1% of the maximum plasma concentrati ons still could be accurately and precisely quantified. Method B was e mployed to determine the drug in plasma after administration of 1 mg a s aerosol.