Pharmaceutica Analytica Acta

Abstract

Pharmacokinetics and Distribution of Florfenicol in Bronchial Secretions of Healthy and Pasteurella multocida Infected Calves

A. Ramadan and A. M. Abd El-Aty

Florfenicol was administered intravenously and intramuscularly at a dose rate of 20 mg/kg bwt to determine its concentration in blood and bronchial secretions as well as kinetic behavior in healthy and diseased calves. Sever acute bronchopneumonia was induced via inoculating the animals with Pasteurella multocida . Following intravenous (i.v) administration, the serum concentration - time curve indicated a two compartment open model with a mean elimination half-lives (t 1/2β ) of 4.10 and 4.84 h in healthy and infected calves, respectively. The mean volumes of distribution at steady state (Vdss) were 0.68 and 0.63 L/kg and the total body clearances (C ltot ) were 0.15 and 0.11 L/kg/h with mean residence time (MRT) of 0.05 and 0.05 h, respectively. Florfenicol was slowly eliminated from serum and bronchial secretions with elimination half-lives (t 1/2el ) of (12.43 and 17.23 h) and (13.74 and 22.46 h), respectively, following intramuscular (i.m.) injection. The peak concentrations (Cmax) in serum and bronchial secretions were (3.70 and 4.06 μg/ml) and (6.88 and 7.62 μg/ml) attained at (3.07 and 3.01 h) and (1.54 and 1.70 h), respectively. The drug is extensively distributed to bronchial secretions with AUC bronchial secretion / AUC serum ratio of 1: 2.53 and 1: 2.03, respectively. The clinical and hematological parameters in calves treated intramuscularly returned to normal faster than those treated intravenously. These results suggest that i.m. injection of florfenicol could be used for treatment of acute P. multocida bronchopneumonia in calves.