Pharmacokinetic profile of florfenicol in bovine plasma

Florfenicol is an antibiotic that is used to treat respiratory infections and other diseases in cattle. An understanding of its pharmacokinetics is important for effective and appropriate infection control, with the goal of minimizing the development of resistant bacterial strains. This study aimed to determine the pharmacokinetic profile of florfenicol in bovine plasma after two doses of intramuscular injection and assess its efficacy against susceptible bacteria. Eight cows were given two intramuscular injections of florfenicol at doses of 20 mg/kg at intervals of 48 hours. The plasma concentration was determined via high-performance liquid chromatography coupled with a mass spectrometer. The minimum inhibitory concentration (MIC) was assessed according to the international standards of the Clinical and Laboratory Standard Institute. The following pharmacokinetic parameters were calculated: C_max=1.21±0.25 µg/mL, T_max=3.43±2.23 h, AUC_0-t=34.16±4.50 h.µg/mL, T_½=63.46±23.76 h and C_max=1.17±0.20 µg/mL, T_max=6.00±0.00 h, AUC_0-t=52.37±5.50 h.µg/mL, and T_½=77.74±43.65 h for the first and second injections, respectively. The following plasma florfenicol levels remained above the bacterial MIC: Mannheimia haemolytica (0.75 µg/mL), Pasteurella multocida capsular type A (0.75 µg/mL) and Histophilus somni (0.30 µg/mL). These results prove the efficacy of florfenicol against bacteria that cause respiratory disease in cattle.