Pharmacokinetics and biliary concentrations of fleroxacin in cholecystectomized patients

Abstract

Patients with biliary tract infections received 800 mg of fleroxacin orally once daily on five consecutive days; cholecystectomy was on day 3. Starting on the day when dose 5 was administered, serial blood and T-drain bile samples were taken for 72 h and urine was collected for 96 h. The mean (+/- the standard deviation) peak concentration in plasma was 8.2 +/- 4.0 mg/liter at 8.3 h. The harmonic mean elimination half-life was 10.5 h, which is comparable to that reported for healthy volunteers. This increase resulted from reduced renal clearance (mean [+/- standard deviation], 38 +/- 22 ml/min), as the volume of distribution in the patients (1.4 +/- 0.7 liter/kg) did not differ from that reported for healthy subjects. Maximum concentrations in T-drain bile were high (median, 22.1 mg/liter) and exceeded those measured in plasma by a factor of 2 to 3; the individual ratios of the area under the curve for bile divided by that for plasma ranged from 1.3 to 9.9. As observed in healthy volunteers, the major pathway for elimination of fleroxacin was via the kidneys. The fraction of dose 5 eliminated in the 0- to 24-h urine was reduced, however, and the fraction of the dose in the urine as the N-demethyl and N-oxide metabolites was elevated. At the dose regimen used in this study, the MICs for most pathogens that cause biliary tract infections were surpassed in plasma and bile for more than 24 h.