Penetration of fleroxacin into human and animal tissues

Fleroxacin concentrations in human and rat tissues were determined by HPLC following extraction with dichloromethane:isopropanol. This method yielded a high recovery of more than 85%. In the investigated tissues the fleroxacin levels were equal to or higher than those concomitantly measured in plasma. The concentration ratios 'tissue/plasma' were 1.6-2.7 for lung, 1.9-2.1 for muscle, 1.1-1.9 for gynaecological tissues and 1.2 for bone. Only in the case of fat and lens/eye lower ratios of 0.05-0.5 were found. The actual measured fleroxacin concentrations in most tissues and in plasma were high. Following oral administration of the recommended therapeutic dose of 400 mg, once daily, peak concentrations of 5-6 mg/l were reached in human plasma at steady state. Even 24 h after drug intake the fleroxacin level was still approximately 1 mg/l and thus in the range of the MIC90 values of susceptible bacteria causative for many types of tissue infections.