Studies On The Determination Of Tulathromycin Residues By LC-MS/MS And The Application Of Evaluation Of Tulathromycin In Chicken Tissues

As a new veterinary medicine,Tulathromycin has been widely used in clinical medicine for its absorption of rapid and high bioavailability.The use of drugs may remain within the animal source of food,thereby endangering human health through the food chain.A high performance liquid chromatography tandem mass spectrometry(HPLC-MS/MS)for the determination of Tulathromycin was established in chicken,liver,kidney and plasma.Pharmacokinetic and safety of Tulathromycin were further investigated in chicken.Samples were extracted with acetonitrile and defatted with hexane and cleaned up by LC-SCX cartridge.The separation of Tulathromycin was performed on Agilent 1100 system with Luna C18(2)column and the elution solvent of acetonitrile and 0.1% formic acid-water at a flow rate of 0.2 mL/min as the mobile phase.The identification of Tulathromycin was carried out by positive electrospray ionization(ESI+)in multiple reaction monitoring(MRM)mode.The plasma and tissues samples were collected in different intervals following single intravenous,intramuscular and oral administration at the dose of 20 mg/kg of body weight respectively,then detected by LC-MS/MS method.The concentration-time data of Tulathromycin in plasma were analyzed with the WinNonlin TM software package.The results showed that the calibration curves for all the tissues were linear(R2 > 0.9900)in range of 5.00~200 ?g/kg.The relative standard deviations(RSDs)were 5.0%~9.2% for intra-day and 5.2%~12.7% fo r inter-day determinations.Samples of plasma,muscle,liver,kidney of Limit of detection(LOD)and limit of quantitation(LOQ)were0.8,0.5,0.8,0.5 ?g/kg and 2,1,2,1 ?g/kg respectively.The Tulathromycin concentration-time data were all fitted to noncompartment model after single intravenous,intramuscular and oral administration to the healthy chickens.The mean pharmacokinetic parameters of Tulathromycin after intravenous administration in chicken were as follows: AUClast was 5.34 ?g·h/mL;CL was 17.71 mL/kg/h;the volume of distribution at steady-state(Vss)was 77.15 L/kg and the elimination t1/2 was 21.65 h.The mean pharmacokinetic parameters of Tulathromycin after intramuscular administration in chickens were as follows: t1/2 20.96 h;AUClast 4.93 ?g·h/mL;tmax was 0.25 h;Cmax was 0.83 ?g/mL;The mean pharmacokinetic parameters of Tulathromycin after oral administration in chickens were as follows: t1/2 was 24.33 h;AUClast was 3.43 ?g·h/mL;tmax was 0.50 h;Cmax was 0.69 ?g/mL.The bioavailability of Tulathromycin after single intramuscular and oral administration were 92.59% and 62.38% respectively.Thirty chickens were randomly allocated to two treatment groups for intravenous and oral administration of Tulathromycin at 20,60,100 mg/kg b.w respectively.A further six chickens were left untreated as controls.The results showed physical examination parameters between treatment and control groups over the 15-day study period revealed no significant differences(P > 0.05).other serum chemical parameters,such as ALB?TP?GOP?GTP?CREA and BUN revealed no significant differences(P > 0.05).No significant differences as time goes on suggesting that a slight effect of injury on chicken was caused by Tulathromycin.