Pharmacokinetics, tissue distribution, and metabolism of flumequine in channel catfish (Ictalurus punctatus)

The pharmacokinetics and metabolism of the fluoroquinolone drug flumequine (FLU) were examined after intravascular (1 mg/kg) or oral (5 mg/kg) dosing in channel catfish. Parent FLU concentrations in plasma declined slowly aft er intravascular dosing, with a half-life of 25 h. After oral dosing, FLU c oncentrations in plasma were highest (3.1 mu g/ml) at 14 h after dosing; ab sorption and elimination half-lives were 4.9 and 22 h, respectively. The or al bioavailability of FLU was 44%, based on normalized plasma data. Plasma protein binding of parent FLU was extensive, but saturable (88%-55% bound a t 0.125-8.0 mu g/ml). After oral dosing with C-14-labeled FLU, radioactive residues were evenly distributed among the major tissues analyzed, with pea k concentrations occurring at 12-24 h. Residue concentrations were highest in liver (6.2 mu g/g) and lowest in muscle (1.8 mu g/g) at 24 h. Only paren t FLU was found in muscle and was eliminated with a half-life of 26 h. FLU and its metabolites were recovered in urine and bile. Residues in bile cons isted almost entirely of a taurine conjugate of FLU. In urine, the taurine conjugate and hydroxy-FLU metabolites were found, in addition to the parent compound. Published by Elsevier Science B.V.