Pharmacokinetics Of Florfenicol In Healthy Ducks And Ducks Infected With Riemerella Anatipestifer

In this study,a high performance liquid chromatography tandem mass spectrometry?HPLC-MS/MS?method was developed for the determination of florfenicol in duck plasma,liver and kidney.The pharmacokinetics properties of florfenicol were described in duck model infected with Riemerella anatipestifer,and the distributionof florfenicol in plasma,liver and kidney were observed.This study may provide guidance for clinical application of florfenicol.In plasma,at adding level of 0.5 ng/mL,2.5 ng/mL and 25 ng/mL,the recovery of florfenicol was between 87.60%¹07.84%with coefficience of variation between2.83%⁹.56%,the limits of detection and quantification were 0.25 ng/mL and 0.5 ng/mL,respectively,in liver,at adding level of 0.5?g/kg,2.5?g/kg and 25?g/kg,the recovery of florfenicol was between 77.45%⁹6.99%,with coefficience of variation between2.45%¹1.49%,the limits of detection and quantification were 0.25?g/kg and 0.5?g/kg,respectively,in kidney,at adding level of 1?g/kg,5?g/kg and 50?g/kg,the recovery of florfenicol was between 76.86%¹00.73%,with coefficience of variation between2.84%¹0.79%,the limits of detection and quantification were 0.25?g/kg and 0.5?g/kg,respectively.The results indicated that this method was sensitive and rapid,which could satisfy with the study of the pharmacokinetics properties.MIC and MBC of florfenicol against Riemerella anatipestifer were determined by broth microdilution.The bactericidal assay and post antibiotic e ffect of florfenicol against Riemerella anatipestifer were studied by colony counting method.The results showed that,the MIC of florfenicol against Riemerella anatipestifer was 1?g/mL,the MBC was 2?g/mL.The results of killing curves and post antibiotic effect,indicates that florfenicol has high bactericidal acivity against Riemerella anatipestifer.Riemerella anatipestifer broth culture?10⁹ CFU/mL?were intramuscular injected into the thigh of ducks.After 6 hours of infection,ducks appeared obvious symptoms,such as depression,anorexia,somnolence et al.During the infection of 6⁹ hours,the amount of bacteria in heart blood was stable at about 10⁶ CFU/mL.This model is simple and repeatable.156 ducks were randomly divided into 2 equal groups of 78 ducks each,one group was infected with Riemerella anatipestifer.The two groups were both injected with florfenicol injection following intramuscular?i.m.?administratio n at a single dosage of 20mg/kg body weight,respectively.Plasma and tissues samples were collected at 0,5,10,20,30,45 minutes and 1,2,4,8,12,24,48 hours after administration.The florfenicol concentration in each samples were analyzed using a HPLC-MS/MS method.The drug concentration-time datas were analyzed by non-compartmental analysis of pharmacokinetic software WinNonlin 5.2.1.The main pharmacokinetic parameters of florfenicol in healthy ducks plasma were as follows:the elimination half-life(t_1/2?)was 4.142 h,the peak time(T_max)was 0.5 h,the peak drug concentration(C_max)was 10.231?g/mL,the area under the drug concentration-time curve(AUC_last)was 25.620?g/mL·h,the apparent distribution volume?Vd/F?was 4.664 L/kg,the total body clearance?CL_B/F?was 0.781 L/h/kg,The main pharmacokinetic parameters of florfenicol in healthy ducks liver were as follows:t1/2?was6.328 h,T_max was 0.5 h,C_max was 5.973?g/g,AUC_last was 13.462?g/mL·h,The main pharmacokinetic parameters of florfenicol in healthy ducks kidney were as follows:t1/2?was 5.295 h,T_max was 0.5 h,C_max was 4.296?g/g,AUC_last was 9.419?g/mL·h.The main pharmacokinetic parameters of florfenicol in infected ducks plasma were as follows:the elimination half-life?t1/2??was 4.250 h,the peak time(T_max)was 0.5 h,the peak drug concentration(C_max)was 9.986?g/mL,the area under the drug concentration-time curve(AUC_last)was 22.791?g/mL·h,the apparent distribution volume?Vd/F?was 5.380 L/kg,the total body clearance?C L_B/F?was 0.876 L/h/kg,The main pharmacokinetic parameters of florfenicol in infected ducks liver were as follows:t1/2?was 8.430 h,T_max was 0.5 h,C_max was 5.973?g/g,AUC_last was 4.390?g/mL·h,The main pharmacokinetic parameters of florfenicol in infected ducks kidney were as follows:t1/2?was 6.988 h,T_max was 0.75 h,C_max was 2.519?g/g,AUC_last was 8.620?g/mL·h.The characteristics of rapid absorption,high plasma concentration,wide distribution and faster elimination in plasma were showed following im florfenicol injection at a single dosage of 20 mg/kg body weight in healthy and infected ducks.In the infected ducks'liver and kidney,AUC_last reduced from 13.461?g/mL·h,9.419?g/mL·h to 4.390?g/mL·h,8.620?g/mL·h,respectively,C_max reduced from 5.973?g/g,4.296?g/g to 1.991?g/g,2.519?g/g,respectively,t_1/2?showed a slight decrease from 6.391 h,5.295 h to 8.430 h,6.988 h,respectively.