Residue Elimination And Safety Of Amoxicillin Dry Suspension In Pigs

Amoxicillin(AMO),known as hydroxyl ampicillin penicillin,is one of the acid-resistant penicillin antibiotics which has been widely used in veterinary clinical practices.The pharmaceutical preparations of amoxicillin were authorized for adhibition in various livestock animals and pets because of the therapeutic effect against infections caused by Gram-positive and Gram-negative bacteria.A series of reports on the elimination and safety of amoxicillin in pigs have been reported,but little is known about the oral administration of amoxicillin dry suspension.This study was centered on the residue elimination and the safety of amoxicillin dry suspension in pigs by oral administration to provide an experimental foundation for the clinical application in pigs.In this study,tissues were extracted with phosphate buffer solution,precipitated the proteins with trichloroacetic acid and purified by HLB solid phase extraction cartridge.The concentration of amoxicillin in the tissue was determined by ultra performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS)and quantified by internal standard method.The results showed a precise linearity at the range of 10～500ng/m L(R~2>0.99),with a LOD of 5μg/kg and a LOQ of 10μg/kg.The recovery was 80.2%～120%with a RSD less than 15%both in intra-and inter-assay.We established a straightforward and stable method for residue detection of amoxicillin in pig tissue.The 21 ternary cross-breeding boars weighing 44.6±2.7kg were selected for the residual elimination experiment.They were randomly divided into 5 groups with 4 pigs in each group according to the different sampling site and 10mg/kg.bw was administered orally twice a day for 5 consecutive days,with 1 pig as blank control.The experimental groups were fed 200g pannage with the corresponding amoxicillin suspension.Muscle,fat,liver and kidney were collected in 12h,1d,3d,5d and 7d by bloodletting after drug withdrawal.The residual concentration of amoxicillin in these tissues was determined by the method described above.The results showed that amoxicillin was detected only in muscle with a concentration less than MRL,while it could not be detected in fat,liver and kidney.Thus,the withdrawal time of amoxicillin was set to 0d according to the measured concentration method.The 24 ternary crossbred pigs weighing 14.9±2.12 kg were selected for the safety experiment.They were randomly divided into 4 groups with 3 males and 3 females in each group.The recommended dose group,triple recommended dose group and quintuple recommended dose group were set according to the 1,3,5 times recommended doses of amoxicillin suspension.The doses of the test group were 10 mg/kg.bw,30mg/kg.bw and50mg/kg.bw,twice a day for 10 days.There was no animal death during the experiment and all pigs showed normal clinical performance.We did not observe the significant change of body temperature caused by amoxicillin dry suspension.The feed conversion rate was reduced as the dose increased.The blood routine test showed that the concentrations of MCH and MCHC were within the normal range and there was no significant difference among each group(P>0.05).The concentrations of RBC,HGB,HCT,MCV,RDW-CV and PLT had the statistical differences among these groups.However,the concentrations of MCV,RDW-CV and PLT were within the normal reference range while the concentrations of RBC,HGB and HCT showed decrease at first and then increase after the experiment,which was slightly deviating from the upper and lower limits of the normal range;Although there was no notable difference of WBC concentration among each group,it approached the normal range on 7d after withdrawal.According to the comparative analysis of serum biochemistry,there was no significant difference in the concentrations of AST,Glu,TG,UA,TBIL,DBIL,ALB,LDH,CK and Ca between the experimental group and the control group(P>0.05);During the administration period,the ALP concentration in the quintuple recommended dose group was significantly higher than that in control group(P<0.05);The concentrations of TC and TP in the three experimental groups were significantly lower than the control group at the end of the experiment(P<0.05);On the 7d after drug withdrawal,the CREA concentration and UREA concentration of control group were significantly lower than the experimental groups(P<0.05);On the 10d after administration and 7d after withdrawal,the phosphorus concentrations in triple recommended dose group and quintuple recommended dose group were notably higher than the control group(P<0.05);On the 10d of administration,the ALT concentration in the quintuple recommended dose group was significantly higher than that in control group(P<0.05),theγ-GT value of the recommended dose group was significantly lower than that of the blank control group(P<0.05).On the 5d of administration,the Mg of the test group was significantly lower than that of the blank control group(P<0.05).By the 10d of administration,the Mg of the test group was significantly higher than that of the blank control group(P<0.05).The pathological anatomical results of pigs showed that the organ tissues such heart,liver,spleen,kidney,stomach and lymph nodes in the quintuple recommended dose group were normal compared with the control group,while plasma cells and lymphocytes infiltrated in the lamina propria of the duodenum.Meanwhile,focal emphysema and lymphocyte infiltration were found in lug tissue.Amoxicillin dry suspension has no adverse effects on pigs at the recommended dosage and only caused repairable injury to the duodenum and lung when it was used for 10 days at quintuple recommended dose according to the blood routine test and the serum biochemicals.In summary,amoxicillin dry suspension should be used in clinical application according to the recommended dose and course of treatment to ensure the safety of pigs.