Studies on Pharmacokinetics of Florfenicol in Chicken and Its Post-antibiotic Effects in Vivo

To investigate pharmacokinetic characteristics of florfenicol and determine its PAE,concentration of florfenicol in chicken serum were determined by bioassay.The infected tissue cage model was developed by implanting two plastic tissue cages in chicken's subcutaneous tissue,The post-antibiotic effects(PAE)of florfenicol in vivo against Pasteurella multocida were tested by routine colonial counting method.The pharmacokinetics showed that the concentration course of florfenicol in serum following its oral administration(30 mg/kg)in chicken could be described by one-compartment open model with first-order absorption.The equation was shown below:C=4.780 4(e-0.109 6t-e-2.585 8t).The primary parameters were as follows:t1/2Ka =(0.28±0.07)h,t1/2Ke=(6.42±0.83)h,tmax=(1.32±0.26)h,Cmax=(3.96±0.42)μg/mL,AUC=(42.41±7.50)(μg/mL)·h-1.The results showed that florfenicol could be absorbed quickly,the elimination half life was long.PAEs of 2MIC,4MIC and 8MIC were 0.35,1.20 and 1.48 h in vivo,0.23,0.93 and 1.17 h in vitro respectively,after the exposure to the drug in vitro for 1 h.The ideal dosage regime was suggested that chicken could take florfenicol once daily with oral administration of 30mg/kg b.w.