DETERMINATION OF BAY-12-8039, A NEW 8-METHOXYQUINOLONE, IN HUMAN-BODYFLUIDS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE DETECTION USING ON-COLUMN FOCUSING

A reversed-phase (RP) high-performance liquid chromatographic (HPLC) m ethod with fluorescence detection allowing the sensitive and specific quantification of BAY 12-8039, a new antimicrobially active 8-methoxyq uinolone, in biological fluids is described, The method is compared to a microbiological assay (bioassay) based on B. subtilis test strain w ith a limit of quantification of approximately 60 mu g/l. Following di lution and centrifugation, plasma, saliva or urine supernatant is dire ctly injected onto the HPLC system. Concentrations down to a limit of quantification of 2.5 mu g/l can be quantified in plasma, saliva and u rine. Data on recovery, accuracy and precision of the method throughou t the whole working range as well as results on stability of the analy te are presented. The concentration data are correlated with results f rom the bioassay. BAY 12-8039 is stable in plasma after repeated freez e-thaw cycles and following storage at -20 degrees C for at least 12 m onths. The results of HPLC measurements excellently agree with bioassa y data indicating the relevance of the method as a tool in clinical de velopment to answer pharmacokinetic questions related to antimicrobial activity. The method was applied to human plasma, saliva and urine fr om subjects after a single oral dose of 400 mg of BAY 12-8039. (C) 199 7 Elsevier Science B.V.