Concentrations of
fleroxacin in human body fluids and tissues were studied to obtain information about the efficacy of the
drug at the site of
infection and the ratio of
fleroxacin concentrations in tissue or fluid versus those in plasma as a measure of the extent of penetration. Samples of body fluids and tissues were obtained at various intervals after
oral administration, and
fleroxacin concentrations were determined by high-performance liquid chromatography. After administration of the standard dose of 400 mg once daily, the maximal plasma concentrations were 5-7 mg/L at steady-state and the minimal concentrations were approximately 1 mg/L at the end of the dosing interval. In most
biologic specimens, such as myometrium, fallopian tube, bile bladder wall, bone, tonsils, maxillary sinus mucosa,
prostatic adenoma, sputum, inflammatory fluid, synovia, lymph, saliva, and tears, the levels of
fleroxacin were similar to those in plasma. In bile, nasal secretions, seminal fluid, lung, bronchial mucosa, and ovaries, the
drug concentrations were 2-3 times higher than those in plasma. Penetration of
fleroxacin into fat, lens, bronchial secretions, sweat, and aqueous humor was limited, with
drug levels reaching only 10-40% of the concomitant levels in plasma. The measured concentration ratios did not vary markedly with time, and the decline in
drug concentrations in tissues and fluids was generally parallel to that in plasma. The breakpoint for susceptibility is 1 micrograms/mL. The susceptibility breakpoint was exceeded by the
drug concentration in plasma for the entire dosing interval and was also reached or exceeded in most body tissues and fluids.