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

Background: 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. Aims: 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. Methods: 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. Results: 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. Conclusion: 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.