Study On The Pharmacokinetics Of Fluazuron And Its Residue Elimination In Cattle Tissues

Fluazuron(FZN) is a insect development inhibitor which controls the ectoparasite of ruminant animals like cattle tick Boophilus microplus, present in tropical areas including Australia, South Africa and Canada etc. It is not currently for veterinary clinical use in China and its maxium residue level is accordingly not regulated in animal foods in our country. In this pqper, the pharmacokinetic of FZN was studied on cow, high pressure liquid chromatography (HPLC) methods were established to determine the concentration of FZN in serum and in tissues of cattle. The elimination of FZN residue in muscle, liver, kidney and fat of cattle was also investigated.The pharmacokinetics of FZN was carried through the nonlactating Holstein cows administrated by1.5mg/kg bw and3mg/kg bw subcutaneous injection respectively with3P97software program. Results showed the absorption of FZN was few and slow with more half time of elimination. The concentration-time curves of FZN were described by one-compartment open model with first-order absorption and the pharmacokinetics parameters were no observably difference between1.5and3.0mg/kg bw dose groups. The main pharmacokinetic parameters were as follows:t1/2kα(15.800±0.230)h, t1/2ke (55.423±1.620) h, T(peak)(46.168±3.979) h, AUC (8.212±0.178) mg/L·h, C(max)(0.066±0.005) mg/L at1.5mg/kg bw dose.A HPLC method was delveloped for determining residues of FZN in cattles. A C18column with ultraviolet absorption detection at260nm, using velocity1.2mL/min, acetonitrilel-water (68/32, v/v) as eluent solution was used in HPLC. The sample was extracted with acetonitrile, cleaned up by Florisil solid phase extract little column. At the fortified levels of0.08,1.0and10mg/kg of FZN. the mean recoveries ranged from82.00%～94.59%in muscle,81.86%～95.39%in kidney,81.89%～95.26%in liver,80.84%～95.24%in fat. The limit of detection (LOD) was0.02mg/kg, the limit of quantification (LOQ) was0.08mg/kg. The established method can be used for the residue analysis of FZN in cattle tissues.The residue elimination of FZN in cattle muscle, liver, kidney and fat tissues was conducted by1.5mg/kg bw subcutaneous injection. Results reflected the information of lower depletion of FZN in tissues and the highest residue level was in different fat tissue at any withdrawal time, fat may be the target residue tissue. The content of FZN residue was fat>> liver> kidney> muscle. The maximum residue of FZN in muscle and kidney was at8weeks post administration and was not detectable after10weeks. The peak residue in liver,and fat tissues was at10weeks withdrawal time, lower than or approached the LOD level at16weeks in liver, but higher than the LOD in fat tissue at16weeks injected. There was no obvious difference between different fats like subcutaneous, abdominal and renal fat in FZN residue level (P>0.05). The residue content of FZN in cattle tissues were not excessed the MRLs regulated by Joint Expert Committee on Food Additives (JECFA).