Comparative Study On Pharmacokinetics Of Four Long-Acting Injectable Formulations Of Enrofloxacin In Pigs

A comparative study on pharmacokinetics of four long-acting enrofloxacin injectable formulations was investigated in 36 healthy pigs after intramuscular injection according to the recommended single dose @ 2.5 mg/kg body weight. The drug concentrations in the plasma were computed using high-performance liquid chromatography (HPLC) with fluorescence detection. WinNonLin5.2.1 software was used to analyze the experimental data and compared it under one-way ANOVA using SPSS software with a 95% confidence interval (CI). The main pharmacokinetic parameters, that is, the maximum plasma concentrations (C-max), the time to maximum concentration (T-max), area under the time curve concentration (AUC(all)) and Terminal half-life (T-1/2) were 733.84 +/- 129.87, 917.00 +/- 240.13, 694.84 +/- 163.49, 621.98 +/- 227.25 ng/ml, 2.19 +/- 0.0.66, 1.50 +/- 0.37, 2.89 +/- 0.24, 0.34 +/- 0.13 h, 7754.43 +/- 2887.16, 8084.11 +/- 1543.98, 7369.42 +/- 2334.99, 4194.10 +/- 1186.62 ng h/ml, 10.48 +/- 2.72, 10.37 +/- 2.38, 10.20 +/- 2.81, and 10.61 +/- 0.86 h for 10% enrofloxacin (Alkali), 20% enrofloxacin (Acidic), Yangkang and control drug Nuokang (R) respectively. There were significant differences among C-max, T-max, and AUC(all) of three formulations compare with that of the reference formulation. No significant differences were observed among the T-1/2 for tested formulations compare with the reference formulation. The pharmacokinetic parameters showed that the tested formulations were somewhat better compared to the reference one. The calculated PK/PD indices were effective for bacteria such as Actinobacillus pleuropneumoniae and Pasteurella multocida with values higher than the cut-off points (C-max/MIC90 >= 10-12 and AUC/MIC90 >= 125). However, they were not effective against bacteria like Haemophilus parasuis, Streptococcus suis, E. coli, and Bordetella bronchiseptica where lower values were obtained.