Residue Dynamics of Enrofloxacin in Scophthalmus maximus,Paralichthys olivaceus and Cynoglossus semilaevis

Abstract:

In this study we compared the elimination rates of enrofloxacin in 3 major aquacultured flatfish, turbot (Scophthalmus maximus), olive flounder (Paralichthys olivaceus) and tongue sole (Cynoglossus semilaevis), in 20℃ seawater after the oral drug administration. Healthy turbot, olive flounder and tongue sole weighing 300-400 g were selected and orally administered with enrofloxacin for 3 consecutive days. Plasma and various tissues, such as liver, gill, muscle and kidney, were sampled on 1, 3, 6, 10, 15, 20, 25, 30, 35, and 40 days post drug administration, and the enrofloxacin concentration in these tissues were determined using reversed-phase high performance liquid chromatography (HPLC). The elimination curves of enrofloxacin for 3 flatfish species were plotted as concentration versus time, and the half-lives of the drug were calculated. It was found that in all 3 species the concentration of enrofloxacin residue was higher in kidney than in other tissues. Elimination of enrofloxacin in kidney of olive flounder was the fastest among the 3 flatfish species, followed by turbot and then tongue sole. Half-lives in the 3 species were 3.75, 6.54 and 7.37 days respectively. As for drug elimination in plasma, enrofloxacin was removed slower than its metabolite ciprofloxacin. Overall, elimination of enrofloxacin was the fastest in olive flounder followed by turbot, and it was the slowest in tongue sole. In China, the maximum residue limit (MRL) of enrofloxacin in seafood was 50 μg/kg, therefore the withdrawal periods of enrofloxacin for farmed turbot, olive flounder and tongue sole should be at least 44, 33 and 47 days respectively.