Integrated Pharmacokinetic–Pharmacodynamic(PK/PD) Model Of Marbofloxacin In Pigs Infected With Pasteurella Multocida

In the present study,the pharmacokinetic properties of marbofloxacin in pig were characterized by using a tissue cage model infected with P.multocida in pigs.The distribution and penetration rate of marbofloxacin into the tissue cage fluid?TCF?were studied.The in vivo activities of marbofloxacin against a pathogenic strain of P.multocida were determined in TCF.The in vivo PK/PD model of marbofloxacin against P.multocida was established.It was proposed that those models be used to provide a rational basis for designing dosage regimen,which will provide information for medicine usage in clinical situation.The MIC?0.125?g/m L?of marbofloxacin against the investigated CVCC 434 in TCF was determined by an agar dilution method as a preliminary screening,according to Clinical and Laboratory Standards Institute?CLSI?reference methods.Protein binding of marbofloxacin in serum and tissue cage fluid were performed using ultrafiltration.The results indicated that the percentage of protein bound fraction of marbofloxacin in serum and tissue cage fluid were 47.89%±1.86%and 52.90%±3.30%respectively,when marbofloxacin concentrations ranged from 0.01?g/mL to 2?g/mL.Protein binding of marbofloxacin in TCF and serum were both non-concentration dependent.Optimized the extracting method of marbofloxacin in TCF,the high performance liquid chomatography?HPLC?was used to detect marbofloxacin concentration in TCF with a fluorescence detector.Ofloxacin was selected as the internal standard and the drug was extracted by the trichloromethane.Absolute recoveries of marbofloxacin in the TCF were>85%and coefficients of variation were<10%for both within runs and between runs.The limit of quantification of marbofloxacin in TCF was 0.01?g/m L and the limit of detection was0.005?g/mL.The results indicated that this method was rapid,simple,reliable and sensitive,which could satisfy with the subsequent study.24 h after 0.5 m L of P.multocida saline suspension(².0×10⁸ CFU/mL)were injected into the sterile tissue-cages,the bacterial count rise to 10⁹ CFU/mL,and then the stabilized tissue cage infection model was established.Nine groups were treated with series dosages of marbofloxacin injection?10%?0.15,0.3,0.5,0.8,1.0,1.3,1.6,2.0,2.5 mg/kg as body weight intramuscularly.0.5 m L of TCF samples were aspirated from the tissue-cages by percutaneous puncture at 0,3,6,9,12and 24 h after dosing,for determining the antimicrobial activity and establishing the time killing curve.At the same time TCF?0.5 ml?were sampled 1,3,6,9,12,24,30,36,48,72 and 96 h after the injection of drug,for determining the marbofloxacin concentration.Marbofloxacin concentration-time data were analyzed by a Non-compartment Model offered by WinNonlin 5.2.1 software.The acquired PK parameters showed that the C_max and AUC₂₄ had a liner relationship with the dosages.The main PK parameters of a single dosage?2.5mg/kg?to pigs by im were presented as follows:T_max=?5±1.41?h,C_max=?0.71±0.09??g/mL,AUC₂₄=?21.06±3.69??g/mL·h,T_1/2?=?20.91±8.57?h,MRT=22.48±2.37h?An Inhibitory Effect Sigmoid E_max offered by WinNonlin5.2.1 was applied to analysis the PK and PD data.The results showed that AUC₂₄/MIC was the best PK/PD parameter for predicting the antimicrobial activity of marbofloxacin against P.multocida?R²=0.9257?.Magnitudes of AUC₂₄/MIC predicted for,1log reduction and 3 lg reduction?bactericidal?were 13.48 h and 57.70 h.Marbofloxacin presented excellent antimicrobial activity against P.multocida in TCF.