Pharmacokinetics And Safety Evaluation Of Tildipirosin Injection In Pigs

Tildipirosin is a semi-synthetic tylosin analog,which is a novel 16-membered-ring macrolide antimicrobial.It has a broad spectrum of activity against major SRD pathogens like Actinobacillus pleuropneumoniae and Haemophilus（H.）parasuis.This study was designed to determine plasma concentrations of Tildipirosin after intravenous and intrauterine administrations of Tildipirosin to pigs,and evaluated the safety of Tildipirosin injection.The pharmacokinetics of Tildipirosin in pigs:This study was designed to determine plasma concentrations of Tildipirosin after intravenous and intrauterine administrations of Tildipirosin to pigs,and evaluate the feasibility to promote the drug concentration in target tissues by changing the administration route.20 cross-bred（Landrace×Yorkshirech×duroc）healthy,non-lactating pigs at about 8 weeks,were used.The pigs were randomly divided into two groups.The first groups was administered with Tildipirosin injection by intravenous route,at a single dose of 4 mg·kg^-1 body weight;whereas the second group was administered with Tildipirosin injection by intrauterine administration.Tildipirosin concentrations were determined by high performance liquid chromatography with Tandem mass spectrometry.A non-compartmental analysis of drug plasma concentration vs.time profiles was performed with pharmacokinetic modeling using Winnonlin software.Following intravenous administration,the main pharmacokinetic parameters were as follows:t_1/2,（99.43±22.25）h;V_d,（36.6±17.48）L·kg^-1;Cl,（260±84.33）mL·h^-1·kg^-1;AUC_0-t,（18030.30±7560.75）ng·h·L^-1,AUC_0-∞（18795.31±7455.27）ng·h·L^-1.The absorption of Tildipirosin was rapid and well absorbed after intrauterine administration,with t_1/2 of 100.83±20.23 h,t_max of 0.51±0.29 h,C_max of 886±156 ng·mL^-1,AUC_0-t of19702.05±6442.36 ng·h·L^-1,AUC_0-∞of 20840.08±6849.76 ng·h·L^-1.The absolute bioavailability（F）was 91.5%.The results showed that the pigs can absorb Tildipirosin well by way of intrauterine administration,with slowly eliminated and high bioavailability.And the effect on body after intrauterine administration should be considered.The safety evaluation of Tildipirosin injection in pigs:Twenty four pigs weighted about 15 kg were devided into groups randomly（n=6,each group）.Pigs in different group were given doses Tildipirosin of 0 mg/kg（control）,4 mg/kg（recommend dose）,8 mg/kg（three times of recommend dose）,12 mg/kg（five times of recommend dose）by intrauterine administration.Its safety was evaluated through clinical observation,means of blood routine,indexes of blood biochemical inspection on the day 0,7,14 after intrauterine administration,pathological anatomy and histological observation.Among four groups,the clinical observations were normal,so did the means of blood routine(RBC、HGB、HCT、MCV、MCH、MCHC and PLT（P>0.05）.During the administration,According to the serum physio-biochemical indices,the indices with no significant changes in all experimental groups pre and post experiment are as followed:LDH、T-Bil、ALP、CK、AST、TG、γ-GT.The indices that showed significant change are Crea、UREA and Gluon day 14（P<0.05）.Indexes of UA、TP、ALT、GLB、P、Mg and TC in group of three-time and five-time recommended doses were significantly changed on day 7（P<0.05）,but they became normal again on day 14.Moreover,there were several hepatic petechias in the group of five-time recommended dose in pathological anatomy and histological observation.The results shows that recommend dose of Tildipirosin injection had no significant effect on blood and blood biochemical indexes,while no significant change appeared in tissue pathology.However,high-dose Tildipirosin injection may impair the heart.