High-performance liquid chromatographic assay and erythrocyte partitioning of fleroxacin, a new fluoroquinolone antibiotic.

A rapid technique for sample preparation and HPLC was developed to study in vitro the erythrocyte binding and plasma protein binding of fleroxacin in the concentration range 0.2-15 micrograms ml-1. The red blood cell partition coefficient of fleroxacin was 1.45 +/- 0.18 at 25 degrees C and was independent of concentration, incubation time and temperature. The in vitro plasma protein binding of fleroxacin in humans, determined by two independent methods, was 47-51%. Partition studies using erythrocytes as a simple in vitro model may be useful to predict the degree of tissue uptake and the volume of distribution.