Study On Pharmacokinetics And Residue Elimination Of Moxidectin Pour-on Administration In Chicken

With the wide application of traditional macrolide insecticides in veterinary clinic,insect resistance has emerged one after another,which brings some difficulties to the prevention and treatment of clinical parasitic diseases.Moxidectin is a new generation of lipid repellent in macrocycle,which can effectively kill Nematoda and surface parasites,and its efficacy is long-lasting.The purpose of this experiment was to establish a detection method for the content of Moxidectin in chicken plasma and tissues（muscle,liver,kidney and sebum）,analyze the pharmacokinetics and residue elimination law of Moxidectin in chicken,and determine the withdrawal period of Moxidectin in chicken tissues with reference to the maximum residue limit standard.It provides a theoretical basis for the application of Moxidectin in poultry parasite control in the future.The specific research contents are as follows:1.Establishment of HPLC-MS/MS method for the determination of Moxidectin in chicken plasma and tissue.In order to study the pharmacokinetics and residue elimination of Moxidectin in chicken,a high performance liquid chromatography tandem mass spectrometry（HPLC-MS/MS）method for the determination of Moxidectin in chicken plasma and tissue was established.Chicken blood plasma was extracted by acetonitrile,vortex and centrifugation.The supernatant was dried under nitrogen flow,redissolved with acetonitrile,0.22μm filter membrane filtration,to be tested on the machine.Chicken muscle,liver and kidney were extracted with 2%ammoniated acetonitrile,the supernatant was taken by vortex and centrifugation,degreased with n-hexane,dried under nitrogen flow,redissolved with acetonitrile,0.22μm filter membrane filtration,to be tested on the machine.Chicken sebum was extracted by ethyl acetate acetonitrile（1:9,v/v）,the supernatant was taken by vortex and centrifugation,purified and degreased by Prime HLB column,all eluents were collected,dried under nitrogen flow,redissolved with acetonitrile,0.22μm filter membrane filtration,to be tested on the machine.HPLC-MS/MS detection chromatographic conditions:the chromatographic column is Agilent rrhd eclipse plus C18 column（2.1×50 mm,1.8μm）Mobile phase A is 0.1%formic acid water and B is pure acetonitrile.Detected by gradient elution procedure.The results showed that the linear relationship of Moxidectin in plasma and tissue was good in the range of 1～200 ng/m L（ng/g）（R²>0.998）,LOD was 0.2 ng/m L in plasma and 0.3 ng/g in tissue;LOQ was 1.0 ng/m L in plasma and 1.0 ng/g in tissue.The recoveries of Moxidectin in plasma and tissue ranged from 91.83%to 108.33%.The intra day and inter day precision RSD of plasma and tissue quality control samples were less than 4.10%,and the stability coefficient of variation CV was no more than 6.53%.The results showed that the established detection method met the test requirements of pharmacokinetics and drug residue elimination law.2.Pharmacokinetics of Moxidectin pour-on administration in chicken.Twenty cocks weighing 2.0±0.5 kg were randomly selected and divided into two groups.They were poured with Moxidectin pour-on administration or oral Moxidectin oral administration according to 0.2 mg/kg B.W.Blood was collected within 15,30 minutes,1,2,4,8,12 and 24 hours after administration.After centrifugation at 3000 r/min for 5minutes,the obtained plasma samples were stored at-18℃.After the samples were detected by established HPLC-MS/MS,the concentration of Moxidectin in plasma samples was obtained.The pharmacokinetic parameters of the two modes of administration were analyzed by pharmacokinetic software.The results showed that the C_maxof Moxidectin oral administration group was 13.09±1.55 ng/m L and that of pour-on administration group was 10.48±1.56 ng/m L,with significant difference（P<0.05）;The AUC of oral administration group（66.38±13.50 h·ng/m L）was significantly higher than that of pour-on administration group（47.25±13.99 h·ng/m L）（P<0.01）;The CL of oral administration group（3176.93±905.87 m L/h/kg）was significantly lower than that of pour-on administration group（6925.39±3542.47 m L/h/kg）（P<0.01）.There was no significant difference in T_1/2β,T_max,VD and MRT of pour-on and oral administration group（P>0.05）.The blood concentration of Moxidectin orally administered in chicken is higher than that of pour-on administration,the efficacy is more lasting,and the clearance rate is lower.3.Study on the elimination of drug residues of Moxidectin pour-on administration in chicken.Forty two cocks weighing 2.0±0.5 kg were randomly selected,and 0.2 mg/kg B.W.of Moxidectin was poured on the back.5 g of muscle,liver,kidney and sebum were collected on the 1st,5th,10th,20th,25th,30th and 35th days after administration,and stored at-18℃.The samples were processed after thawing,detected Moxidectin residues by HPLC-MS/MS.According to the regulations,the drug withdrawal period shall be determined according to the time when the upper limit of the 95%confidence interval of the residue is lower than the maximum residue limit.Finally,the drug withdrawal periods for muscle,liver,kidney and sebum are determined to be 2.6 days,12.2 days,1.6 days and 2.4 days respectively.It is suggested that the drug withdrawal period after Moxidectin pour-on administration is applied to chicken is 13 days.