Determination of BAY x 7195, a novel leukotriene D4 antagonist, in human plasma by high-performance liquid chromatography with post-column photo derivatisation and fluorescence detection.

Methods to determine plasma concentrations of the leukotriene D4 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 micrograms/l (method A). Sensitivity was further enhanced to a LOQ of 0.6 microgram/l 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.