Pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin in flounder Paralichthys olivaceus

Abstract:

In this study we investigated the pharmacokinetics and elimination of enrofloxacin (ENRO) and its metabolite ciprofloxacin (CIP) in Paralichthys olivaceus. After the oral administration of a single dose at 80 mg/kg•bw, the time courses of concentrations of ENRO and CIP in fish tissues were measured with high-performance liquid chromatography and a fluorescence detector. At 0.25 h, the muscle retained the lowest level of ENRO residues among five tissues (See below). The elimination half-life of ENRO in the five tissues was in the order: gills＞liver＞kidney＞blood＞muscle. ENRO in muscle was eliminated fastest and had the lowest elimination half-life of 67.759 h; hence in the 12th day after the drug withdrawal, ENRO in the muscle was no longer detectable. At 0.25 h, the concentration of CIP residues in different tissues was in the order: liver＞kidney＞blood, while CIP could not be detected in the muscle and gills at the same time. In blood, liver and kidney, ENRO was still detectable in the 22nd day after the drug withdrawal; whereas CIP could not be detected in these tissues since the 7th day. These results indicated that the metabolism and elimination of ENRO in P. olivaceus was relatively slow. We also found that the degradation of ENRO into CIP occurred only in a short period after the ENRO administration. Obviously the elimination of CIP in flounder was much faster than that of ENRO.