Pharmacokinetics Study Of Tinidazole Sodium Chloride Injection Single Dose Intravenous Administration In Canines

Tinidazole is a synthetic 5-nitroimidazole drug,which has been widely used in the treatment of anaerobic bacteria and protozoa infections in human medicine.However,drugs which belong to nitroimidazoles only metronidazole and dimenidazole are used in veterinary medicine.Tinidazole has wide tissue distribution and therapeutic range which make it has broad application prospects in veterinary medicine.The pharmacokinetic(PK)study of singledose intravenous administration of tinidazole sodium chloride injection in canines was conducted,based on establishing and validating the liquid chromatography tandem mass spectrometry(LC-MS/MS)method for the detection of tinidazole in canine plasma.The PK parameters were obtained at 30 mg/kg,15 mg/kg,and 7.5 mg/kg dosage.The investigation was proposed to provide clinical PK data which required for new veterinary drug approval.Meanwhile,the study also provides information on optimizing tinidazole sodium chloride injection dosage regimen.1.Method establishment for the determination of tinidazole in canine plasma by LCMS/MSThe protein was precipitated,and the drug was extracted by adding methanol into canine plasma,after the internal standard work solution of(dexamethasone)was added.Then the supernatant was used for LC-MS/MS analysis.The analyte was separated by C18 column,and the 0.1%formic acid aqueous solution and 0.1%formic acid acetonitrile aqueous solution were used as mobile phase for gradient elution(0.1%formic acid aqueous solution:0.00～1.00 min,80%;2.00～3.00,5%;3.01～3.02,20%),positive ion scanning and multiple reaction monitoring(MRM)mode for detection,and internal standard method for quantification.The results showed that the quantitative range of this method ranges from 10 ng/mL to 30000 ng/mL,the coefficient of determination(r2)was greater than 0.99,and the lower limit of quantification(LLOQ)of the method was 10 ng/mL.At 30 ng/mL,400 ng/mL,24000 ng/mL,and LLOQ addition concentrations,the within-and between-run average accuracy ranged from 90.0%to 112.3%and 94.2%to 105.9%,respectively;The within-and between-run coefficient of variation(CV)ranged from 1.4%to 14.6%and 4.3%to 13.8%,respectively.The LC-MS/MS method for the determination of tinidazole in dog plasma established in this study is appropriate for the PK investigation of tinidazole in canines.2.Pharmacokinetics study of tinidazole sodium chloride injection single dose intravenous administration in caninesA parallel trial design was used.Eighteen beagles were randomly divided into high-,middle-and low-dose groups,each group with 6 canines.Then a single dose of tinidazole sodium chloride injection of 30 mg/kg,15 mg/kg,and 7.5 mg/kg was intravenous administration.Blood samples were collected at the set time points,and plasma was separated.A validated LC-MS/MS method was used to determining tinidazole plasma concentration.The non-compartment model was used to fit PK parameters based on plasma drug concentration time data.The results showed that tinidazole presents linear kinetics after the single dose intravenous administration in canines within the dose range of 7.5 to 30 mg/kg and no significant gender difference in plasma tinidazole concentration.In the high-dose group,AUClast and AUCinf were(72884±14238)ng/mL·h and(73462±13592)ng/mL·h,respectively;The middle-dose group was(33375±5718)ng/mL·h and(34616±6484)ng/mL·h,respectively and the low-dose group was(15009±1940)ng/mL·h and(15680±1989)ng/mL·h,respectively.The peak concentrations(Cmax)of the high-,middle-,and low dose groups were(30817±7731)ng/mL,(16233±2570)ng/mL,and(8027±1351)ng/mL,respectively.After a single dose intravenous administration of tinidazole sodium chloride injection in canines,the elimination half-life(T1/2Z)was(1.84±0.41)h,the clearance(Cl)was(451±46)mL/kg/h,and the disposition phase volume of distribution(Vz)was(1170±209)mL/kg.The results indicate that tinidazole is widely distributed but quickly eliminated in canines.Based on the PK/PD target values of similar drugs and the MIC characteristics of sensitive anaerobic bacteria,preliminarily estimated that the effective 24-hour dose for the treatment of sensitive anaerobic infections is 71.75 mg/kg,and the dosing interval for 15 mg/kg and 30 mg/kg tinidazole sodium chloride injection should not exceed 5.7 h and 11.5 h,respectively.