PHARMACOKINETICS AND RESIDUES OF ENROFLOXACIN IN CHICKENS

The pharmacokinetic properties of enrofloxacin were determined in broi ler chickens after single IV and orally administered doses of 10 mg/kg of body weight. After IV and oral administrations, the plasma concent ration-time graph was characteristic of a two-compartment open model. The elimination half-life and the mean +/- SEM residence time of enrof loxacin for plasma were 10.29 +/- 0.45 and 9.65 +/- 0.48 hours, respec tively, after IV administration and 14.23 +/- 0.46 and 15.30 +/- 0.53 hours, respectively, after oral administration. After single oral admi nistration, enrofloxacin was absorbed slowly, with time to reach maxim al plasma concentration of 1.64 +/- 0.04 hours. Maximal plasma concent ration was 2.44 +/- 0.06 mu g/ml. Oral bioavailability was found to be 64.0 +/- 0.2%. Statistically significant differences between the 2 ro utes of administration were found for the pharmacokinetic variables-ha lf-lives of the distribution and elimination phase and apparent volume of distribution and volume of distribution at steady state. In chicke ns, enrofloxacin was extensively metabolized into ciprofloxacin. Resid ues of enrofloxacin and the major metabolite ciprofloxacin in fat, kid ney, liver, lungs, muscles, and skin were measured in chickens that re ceived an orally administered dose of 10 mg/kg once daily for 4 days. The results indicate that enrofloxacin and ciprofloxacin residues were cleared slowly. Mean muscle, liver, and kidney concentrations of the metabolite ciprofloxacin ranging between 0.020 and 0.075 mu g/g persis ted on day 12 in chickens after dosing. However, at the time of slaugh ter (12 days), enrofloxacin residues were only detected in liver and m ean +/- SEM concentration was 0.025 +/- 0.003 mu g/g.