PHARMACOKINETICS OF FLORFENICOL IN CHANNEL CATFISH(ICTALURUS PUNCTATUS) AT DIFFERENT WATER TEMPERATURES

The pharmacokinetics of florfenicol(FF) was investigated with a single doe of 10mg/kg body weight after oral gavage administration in channel catfish(Ictalurus punctatus) at the water temperature of 18℃ and 28℃.Florfenicol and its metabolite Florfenicol Amine(FFA) concentrations in fish plasma were simultaneously determined using high-performance liquid chromatography(HPLC) with UV detection.Pharmacokinetic parameters were calculated by using the 3p97 Practical Pharmacokinetic Program software.The results showed that the kinetics of the drug was found to be temperature dependent.Plasma concentration-time data of florfenicol were best fitted using a one-compartmental open model at both 18℃ and 28℃ water temperature.The kinetic equation were Cplasma=7.921(e-0.036t-e-0.180t) and Cplasma=9.061(e-0.081t-e-0.301t)at 18℃ and 28℃ respectively.The major pharmacokinetic parameters at water temperature of 18℃ and 28℃ were as follows:the absorption half-time(T1/2kα) 3.845h and 2.301h,respectively;the elimination half-time(T1/2ke) 19.118h and 8.519h,respectively;The time point of the maximum plasma concentration(Tp) 11.136h and 5.953h respectively,Peak plasma concentration(Cmax) were 4.074μg/mL and 4.226μg/mL,respectively;Area under curve(AUC) 174.547μg/mL·h and 81.279μg /mL·h,respectively;Mean residence time(MRT) were 27.581h and 12.290h,respectively.Relatively apparent distributed volume V/F(c) were approached that were 1.512L/kg and 1.580L/kg respectively.Florfenicol administration for preventing and controlling bacterial disease of channel catfish which is recommended to be once two days at 18℃ or once a day at 28℃ with a doe of 10mg/kg body weight by oral administration.The main metablite FFA of FF was-not detected in channel catfish plasma sample.