Determination of the new fluoroquinolone fleroxacin and its N-demethyl and N-oxide metabolites in plasma and urine by high-performance liquid chromatography with fluorescence detection.

A high-performance liquid chromatographic method is described for the determination of the new fluoroquinolone fleroxacin and its metabolites in plasma and urine. Plasma samples are deproteinized with acetonitrile, and, after evaporation and reconstitution of the supernatant, samples are analysed on a reversed-phase column. The limit of quantification is 10-20 ng/ml for the parent drug and 10 ng/ml for the metabolites, using a 0.2-ml sample. Urine samples are diluted with the mobile phase. An aliquot is then injected directly onto the column. The limits of quantification are 1 micrograms/ml for the parent drug and 0.5 micrograms/ml for the metabolites, using a 0.1-ml sample. The method has been successfully applied to pharmacokinetic studies of human volunteers and patients.