Study On Pharmacokinrtics And Residues Of Florfenicol In Red Swamp Crayfish (Procambarus Clarkii)

Florfenicol, the third generation of Chloromycetin with the characteristic of broad-spectrum, high efficiency, safety, animal-specific, has been widely used in aquaculture. This study was designed to develop an determination method for floefenicol and its major metabolite, florfenicol amine, in red swamp crayfish tissues, and then investigated pharmacokinetics and residues depletion of florfenicol in red swamp crayfish, in order to provide useful information for approval of florfencol in crayfish.With technique of liquid-liquid and solid phase extraction, the HLPC method of simultaneous determining florfenicol and florfenicol amine in crayfish tiusses has been developed. The limits of detection of florfenicol and florfenicol amine in hemolymph, muscle and hepatopancreas were O.Olmg/L and 0.015mg/L,0.02mg/kg and 0.03mg/kg, 0.03mg/kg and 0.05mg/kg respectively, The recovery values of florfenicol and florfenicol amine were from 78.8 to 94.2%, relative standard deviations were less than 8.16%. at the range of 0.025-20mg/kg, the regress linear equations and relative coefficients were Y=110.42X-0.355, r=0.99986 and Y=91.116X+0.352, r=0.99873. at the range of 0.05～10 mg/kg, the regress linear equations and relative coefficients of florfenicol and florfenicol amine in muscle and hepatopancreas were Y=110.42X-0.355, r=0.99986 and Y=91.12X+0.352, r=0.99873, Y=109.90X-0.138, r=0.99969 and Y=91.53X+0.366, r=0.99968 respectively. The result showed that this method is suitable for study on pharmacokinetics of florfenicol and the residue determination of florfenicol and florfenicol amine in crayfish.The pharmacokinetics of florfenicol(FF) and its metabolite, florfenicol amine(FFA) was investigated following a single intra-sinus administration(i.v) of 20mg/kg or oral administration(p.o) of 50mg/kg body weight of FF in red swamp crayfish at 21±1℃. FF and FFA concentrations in hemolymph were determined by a high-performance liquid chromatography spectrometry. Hemolymph concentration-time data after i.v. or p.o. administration were analyzed by a non-compartment method of 3p97. following i.v. injection, the elimination half-life(T1/2)the volume of distribution(Vd(ss)), the total body clearance(CL) of FF were 8.26h,14.43L/kg,1.21L·kg/h respectively. the elimination half-life, metabolite rate (MR)of FFA were 20.28h,9.3%. After oral administration, Cmax, Tmax, t1/2 and bioavailability(F) of FF were 2.49mg/kg,1h,10.01h,21.6%. t1/2 and MR of FFA were 16.0h,37.5%.Following a single oral dose of 50mg/kg body weight, florfenicol and florfenicol amine concentrations in muscle and hepatopancreas were simultaneously detected at 6,8, 12,18,24,36h, four crayfish at every sample point. The result reveal that the elimination half-live of florfenicol in hepatopancreas was 16.9h shorter than 21h in muscle. elimination half-live of florfenicol amine were similar in both tiusses. hepatopancreas was the main reservoir of the maker residue(the sum of florfenicol and florfenicol amine) in red swamp crayfish because of higher concentration and slower elimination of the maker residue in it. Withdraw time is more than 5d When the maximum residue is 0.1mg/kg for edible tissues in crayfish.