Disposition kinetics of orbifloxacin in tissues of crucian carp (Carassius auratus) following a single intramuscular administration

Orbifloxacin is being widely used in China to treat fish infections in an extra-label manner, which may cause its potential residues in edible tissues. The purpose of this study was to determine the disposition kinetics of orbifloxacin in crucian carp (Carassius auratus) following intramuscular administration for its further safe application in aquaculture industry. Tissue samples of skin, muscle, kidney, and liver were collected from six crucian carps reared at 25°C at 5, 10, 15, 30, 45 min, 1, 2, 4, 6, 12, 24, 48, 72, and 96 h following a single intramuscular injection at 7.5 mg/kg body weight (BW). The orbifloxacin concentrations in tissues were determined using a high-performance liquid chromatography (HPLC) method with a fluorescence detector, then average concentrations versus time data were subjected to non-compartmental analysis to obtain the kinetic parameters. The peak concentration of 5.68 ± 0.03 µg/g was calculated in kidney at 2 h, followed by muscle (5.51 ± 0.01 µg/g) at 4 h, liver (4.84 ± 0.20 µg/g) at 2 h, and skin (4.27 ± 0.08 µg/g) at 4 h. Area under concentration-time curve was calculated as 79.22, 94.72, 118.65, and 129.02 h·µg/g in kidney, liver, skin, and muscle, respectively. And the elimination half-lives were determined as 18.17, 18.41, 18.77, and 19.11 h in skin, kidney, muscle, and liver, respectively. It was shown that orbifloxacin was well distributed into tissues while relatively slowly eliminated in crucian carp reared at 25°C following a single intramuscular injection.