Penetration of pefloxacin and its desmethyl metabolite into the uroepithelium after a 800-MG single oral dose in human patients

Penetration of pefloxacin into the uroepithelium was studied in 20 patients (10 men and 10 women) receiving a single oral dose of 800 mg. Samples of serum, urine, and uroepithelium were taken 1.8 h (mean) after the dose. Pefloxacin and its active metabolite, norfloxacin, were assayed by liquid chromatography, and the microbiologically active compounds were quantified by a microbiological assay. Both procedures were correlated (r > 0.7); nevertheless, slight differences detected in concentrations depended on the levels of norfloxacin achieved in the biological samples. The serum and tissue concentrations were higher than the concentration of bactericide (4 micrograms.ml-1), except in one case. The uroepithelium concentration of pefloxacin was proportional to the serum concentration (r = 0.79). The urinary concentrations ranged from 1.2 micrograms.ml-1 to 82.4 micrograms.ml-1. The mean norfloxacin/pefloxacin ratios were 3% in serum, 8% in uroepithelium, and 44% in urine. The mean uroepithelium/serum concentration ratios were 1 for pefloxacin and 2.3 for norfloxacin. This result shows that, at a time close to that of the maximum concentration, there is good penetration of pefloxacin and norfloxacin into the uroepithelium.