Abstract: 【Objective and method】The plasma pharmacokinetics and tissue residues of danofloxacin mesylate (DFM) were investigated in goldfish, under experimental field conditions at 20℃ after single oral gavage administration(10 mg·kg-1 b.w). The danofloxacin concentrations in plasma and tissues samples were determined by using reversed-phase high performance liquid chromatography（RP-HPLC） after liquid-liquid extraction. Ofloxacin hydrochloride was selected as internal standard. Plasma concentration-time data of DFM were best fitted using a two-compartmental open model, with absorption, distribution and elimination half-life of 0.63, 4.96 and 47.79 h, respectively. The maximal plasma concentration was 3.23 μg·ml-1, peaking at 2.73 h after dosing. Area under the plasma drug concentration-time curve from 0 to ∞ was 154 μg·h·ml-1. The mean residence time (MRT) was 58.56 h using non-compartmental analysis based on statistical moment theory. 【Results】The results indicated that the concentration of DFM in kidney, liver, plasma, muscle and skin was significantly higher than that in plasma , with elimination half-life of 33, 44, 48, 51 and 177 h, respectively. To compare with other tissues, the elimination of DFM in skin was slowest, which behaved as a reservoir tissues in goldfish. It is proposed that withdrawl period should be not less than 23 days after single oral administration (10 mg·kg-1 bw) of DMF to goldfish at 20℃, according to the maximum residue limit(MRL) of 100 mg·kg-1 in skin.

Key words: Goldfish (Carassius auratus), Danofloxacin mesylate, Pharmacokinetics, Withdrawal period