STUDIES ON ELIMINATION DYNAMICS OF ENROFLOXACIN RESIDUES AND ITS METABOLITES IN CHANNEL CATFISH AT TWO DIFFERENT WATER TEMPERATURES

At water temperature of 18℃ and 28℃, channel catfish was administered orally with enrofloxacin (EF) in dose of 20 mg/kg for 7 days, the time courses of concentrations of enrofloxacin and ciprofloxacin in fish tissues (plasma, muscle, skin, liver and kidney) were measured with high-performance liquid chromatography and a fluorescence detector. The results indicated that elimination of enrofloxacin was different in skin, liver, kidney and muscle at 18℃ and 28℃: the equations of elimination curve of enrofloxacin in skin, liver, kidney and muscle were C=1022.1e^–0.034t, C=2601.3e^–0.046t, C=2903.6e^–0.072t and C=1186.5e^–0.036t, the elimination half-lives were 31.79d, 45.29d, 16.15d and 35.54d at 18℃, respectively; the equations of elimination curve of enrofloxacin were C=8805.5e^–0.04t, C=3154e^–0.08t, C=4145.1e^–0.1t and C=1302.1e^–0.068t, the elimination half-lives were 18.33d, 6.26d, 12.44d and 10.34d at 28℃, respectively. Enrofloxacin was changed into ciprofloxacin, the metabolism and elimination of enrofloxacin in channel catfish was relatively slower; enrofloxacin and ciprofloxacin in the channel catfish tissues could not be found after 150 days at 18℃, and 120 days at 28℃. The predicted withdrawal time was 3240℃·d and 4200℃·d respectively.