• marbofloxacin;
  • pharmacokinetics;
  • residues;
  • crucian carp


Pharmacokinetics and residue elimination of marbofloxacin (MBF) were studied in crucian carp (Carassius auratus, 250±30 g) kept at two water temperatures of 15 and 25 °C. Marbofloxacin concentrations in plasma and tissues were analysed by means of high-performance liquid chromatography using an ultraviolet detector. The limits of detection were 0.02 μg mL−1, 0.02 μg g−1, 0.025 μg g−1, 0.02 μg g−1 and 0.025 μg g−1 in plasma and muscle, skin, liver and kidney respectively. Fish were administered orally at a single dosage of 10 mg kg−1 body weight in the PK group. The data were fitted to two-compartment open models at both temperatures. At 15 °C, the absorption half-life (inline image) and distribution half-life (t1/2α) of the drug were 0.36 and 4.48 h respectively. The corresponding values at 25 °C were 0.23 and 0.87 h respectively. The elimination half-life (t1/2β) was 50.75 h at 15 °C and 25.05 h at 25 °C. The maximum MBF concentration (Cmax) differed little between 15 (6.43 μg mL−1) and 25 °C (8.36 μg mL−1). The time to peak concentration was 1.74 h at 15 °C and 0.78 h at 25 °C. The apparent volume of distribution (Vd/F) of MBF was estimated to be 1.36 and 0.87 L kg−1 at 15 and 25  °C respectively. The area under the concentration–time curve (AUC) was 301.80 μg mL−1 h at 15 °C and 182.80 μg mL−1 h at 25 °C. The total clearance of MBF was computed as 0.03 and 0.05 L h−1 kg−1 at 15 and 25 °C respectively. After repeated oral administration at a dosage of 10 mg kg−1 body weight per day for 3 days, the results showed that the elimination half-lives (inline image) of MBF from all tissues at 15 °C were longer than that at 25 °C. Therefore, water temperature is an important factor to be considered when deciding a reasonable withdrawal time.