Tolerance And Pharmacokinetics Of Enrofloxacin Injection In 1-day-old Chicks

The current bacterial diseases that currently affecting the chicken industry are mainly Gram-negative bacteria and mycoplasma,among which E.coli and salmonellosis are the most common bacterial diseases that endanger the chicken industry.For this reason,it has become a common practice in the chicken industry to administer antibacterial drugs against Gram-negative bacteria through appropriate routes to prevent infection of E.coli and Salmonella in chickens.Enrofloxacin is the first fluoroquinolone drug for animal use only,which plays an important role in preventing and controlling chicken E.coli,Salmonella and Mycoplasma.However,in the intensive chicken breeding,enrofloxacin is easily abused by medicated feeding or drinking,which leads to drug resistance.The tolerance and pharmacokinetic studies of enrofloxacin injection was conducted in 1-day-old chicks,which not only has important reference value for guiding the clinical rational use of enrofloxacin injection,predicting the accumulation characteristics and residue elimination rules of the drug in chicks,but also provides an alternative drug for the prevention and control of bacterial diseases in early breeding of chicks.It is of great significance to reduce the various disadvantages of the current quinolone medicated drinking or feeding method dring the early breeding of chicks,and prevent or delay the development of resistance to fluoroquinolone drugs such as enrofloxacin.1.Torerance of enrofloxacin injection on day-old chicks120 one-day-old yellow-feather broilers were randomly divided into 5 groups in order to study the target animal safety of enrofloxacin injection for one-day-old chicks,multiples of the recommended use level:0,1X,3X,and 5X the maximum recommended dose(2mg/each animal)were administrated repectively.The administration route was subcutaneous injection on one side of the neck,and the injection volume was 0.1 mL for each animal.Observations relating to general health and behavior by trained personnel should be recorded on all animals daily after administration,Food and water consumption should be monitored at appropriate intervals.Body weights should be measured at the beginning,end,and several other appropriate times.Hematology and blood chemistry should be conducted at several points during the study,including at several other appropriate times and end of the study.During the period of 15 days after administration,results showed that all chicks in each dose group had normal clinical manifestations,and hematology and blood biochemical parameters were in within the normal physiological range,it shows that enrofloxacin injection has a high safety by the use of the recommended dosage for 1-day-old chicks,and the chicks canat least tolerated 5 times the recommended dosage without significant adverse reactions to the chicks.2.Establish HPLC method for detecting enrofloxacin and ciprofloxacin in chicken plasmaThe plasma samples were extracted and purified with acetonitrile.The chromatography column was Agilent HP-C18(4.6×250mm,5?m),detected by a fluorescence detector,with an excitation wavelength of 278nm and an emission wavelength of 450 nm.Ethylamine-acetonitrile(82:18,V/V)solution.The results show that the content of enrofloxacin and ciprofloxacin in the plasma has a good linear relationship in the concentration range of 0.05-10 mg/L,and the correlation coefficient is greater than 0.999.The average recovery rate is between 87.26%and 106.36%at the three added concentrations(0.05,0.5,10 mg/L),the intra-day variation coefficient is less than 8.97%,and the intra-day variation coefficient is less than 7.92%.The detection limit and limit of quantitation are 0.01 mg/L and 0.05 mg/L,respectively.The processed enrofloxacin and ciprofloxacin standard solutions can be kept stable for 6 months under-20? frozen storage conditions.The sample tray of the sampler can be stably maintained for 8 hours,and the freeze-thaw cycle has no effect on the stability of the analytes in the plasma.The plasma extraction purification and detection conditions established by this method can be used to accurately determine enrofloxacin and ciprofloxacin in chicken plasma.Content.3.Pharmacokinetic of enrofloxacin injection in day-old chicks240 1-day-old chicks(about 50g)were randomly divided into two dose groups,each chick in one group was subcutaneously administered by a single dose of 1 mg of enrofloxacin injection on one side of the neck(0.1 mL injection volume,equivalent to 20 mg/kg·bw),and in the other group,each chick was administered by a dose of 2 mg(0.1 mL equivalent to 40 mg/kg·bw).Blood samples were collected at predetermined time points after administration,and the content of enrofloxacin and its metabolite ciprofloxacin in the blood samples were measured using a validated high-performance liquid chromatography fluorescence detector.The plasma drug concentration-time data was analyzed by non-compannlent model with WinNolin8.0 software.The main pharmacokinetic parameters of enrofloxacin at the doses of 20 mg/kg bw and 40 mg/kg bw in the one-day-old chicks,respectively,are as follows:T max 8h and 4h,and C max 3.75 ? g/mL and 4.92 ? g/mL,AUC last is 40.45h·? g/mL and 78.2h ? g/mL,t 1/2 is 7.37h and 6.53h,and MRT last is 8.6h And 11.42h,Cl was 0.49L/h/kg.The results showed that the peak absorption time appears early correspondingly,but peak concentration did not Increase proportionally after single-dose subcutaneous injection of enrofloxacin injection in day-old chicks,The peak concentration did not increase in proportion to the dose administered(the ratio of the two is 1:1.31).but AUC is dose-dependent(the ratio of the two is 1:1.93).The results also show that the dose and the age of the chickens had no significant effect on the elimination half-life of enrofloxacin.The main pharmacokinetic parameters of metabolite ciprofloxacin in the one-day-old chicks,are as follows,respectively:T max was 8h and 12h,respectively.C max are 0.46 ? g/mL and 0.54 11 g/mL,AUC last is 3.97h·?g/mL and 6.66h·u g/mL,respectively,and t 1/2 is 4.23h and 5.29h.The results show that the peak time of the active metabolite ciprofloxacin was delayed as the dose was increased after a single-dose subcutaneous injection of enrofloxacin injection in 1-day-old chickenst.There was no dose-related for peak concentration(the ratio of the two was 1:1.17),but AUC has dose-dependent in some certain(the ratio of the two is 1:1.67).Based on the results of the preliminary clinical effectiveness and target animal tolerance experiment,a 20 mg/kg bw(approximately 1 mg/each animal)was recommended to prevent infection of Gram-negative bacteria such as E.coli and Salmonella by subcutaneous injection in day-old chickens for 20%enrofloxacin injection.