Residue depletion of danofloxacin in Yellow River carp (Cyprinus carpio haematopterus) following multiple oral administration

The current research aimed to explore the residue depletion of danofloxacin in Yellow River carp (Cyprinus carpio haematopterus) reared in fresh water at 17.8 ± 0.7 °C after oral administration at 10 mg/kg body weight (BW) daily for five consecutive days. Different samples, including plasma, bile, skin-on muscle, liver, kidney, gill, and intestine, were collected at 1, 4, 8, 12 h, 1, 2, 3, 5, 7, 10, 13, 16, and 19 d after the last administration, and danofloxacin concentrations in all collected samples were quantified by a high-performance liquid chromatography (HPLC) method. Danofloxacin is widely distributed in carp and can be detected in all tissues. The highest concentration (Cmax = 8.149 μg/ml) was observed in the bile. A multi-peak phenomenon was observed for the absorption and distribution of danofloxacin during the period of 0–24 h following the final administration. However, after 24 h, drug concentrations in each tissue gradually decreased. On the 13th day (312h) following the last dosing, drug residues were still detected in other tissues except for plasma and muscle plus skin. The non-compartment model was used to determine the pharmacokinetic values. And the elimination half-life (t1/2λz) of danofloxacin in different samples from fast to slow was muscle plus skin (47.89 h), plasma (59.11 h), kidney (63.54 h), gill (104.61 h), intestine (106.25 h), liver (109.43 h), and bile (170.24 h). Considering a maximum residue limit (MRL) of 0.1 μg/g for danofloxacin in the muscle plus skin, a withdrawal time was finally determined as 10 days based on the upper limit of the one-sided 95% confidence interval.