Plasma and Tissue Depletion of Florfenicol and Florfenicol-amine in Chickens

Chickens were used to investigate plasma disposition of florfenicol after single intravenous (i.v.) and oral dose (20 mg kg−1 body weight) and to study residue depletion of florfenicol and its major metabolite florfenicol-amine after multiple oral doses (40 mg kg−1 body weight, daily for 3 days). Plasma and tissue samples were analyzed using a high-performance liquid chromatography (HPLC) method. After i.v. and oral administration, plasma concentration−time curves were best described by a two-compartment open model. The mean [±standard deviation (SD)] elimination half-life (t 1/2β) of florfenicol in plasma was 7.90 ± 0.48 and 8.34 ± 0.64 h after i.v. and oral administration, respectively. The maximum plasma concentration was 10.23 ± 1.67 μg mL−1, and the interval from oral administration until maximal concentration was 0.63 ± 0.07 h. Oral bioavailability was found to be 87 ± 16%. Florfenicol was converted to florfenicol-amine. After multiple oral dose (40 mg kg−1 body weight, daily for 3 days), in kidney and liver, concentrations of florfenicol (119.34 ± 31.81 and 817.34 ± 91.65 μg kg−1, respectively) and florfenicol-amine (60.67 ± 13.05 and 48.50 ± 13.07 μg kg−1, respectively) persisted for 7 days. The prolonged presence of residues of florfenicol and florfenicol-amine in edible tissues can play an important role in human food safety, because the compounds could give rise to a possible health risk. A withdrawal time of 6 days was necessary to ensure that the residues of florfenicol were less than the maximal residue limits or tolerance established by the European Union.