Abstract: 【Objective】The pharmacokinetic properties of florfenicol were studied and compared in both healthy ducks and ducks infected with Riemerella anatipestifer after intramuscular administration.【Method】A total of 240 ducks were randomly divided into 2 equal groups of 120 ducks each, one groups infected with Riemerella anatipestifer in the thigh. The two groups were injected with florfenicol injection following intramuscular (i.m.) administration at a single dosage of 30 mg·kg^-1 body weight, respectively. Plasma samples were collected at 0, 5, 10, 15, 20, 30, 45 minutes and 1, 1.5, 2, 4, 6, 8, 10, and 14 hours after administration. The florfenicol concentration in plasma samples was analyzed using a high performance liquid chromatography (HPLC) method, with UV detector at 223 nm. The mobile phase (acetonitrile:water v/v 26/74) was delivered at a constant flow rate of 1mL·min^-1. The column used was an Agilent C₁₈ (4.6 mm×150 mm, 5 μm) column. A 20 μL aliquot of the reconstituted sample was injected onto the HPLC column. The drug concentration-time data were analyzed by non-compartmental analysis of pharmacokinetic software WinNonlin 5.2.1. Statistical analysis of pharmacokinetic parameters was carried out by statistical software SPSS17.0.【Result】The main pharmacokinetic parameters in healthy and infected ducks were as follows : the elimination half-life (t_1/2β) was (2.57±0.51) h and (2.74±0.54) h. the peak time (T_max) was (0.54±0.14) h and (0.55±0.18) h. the peak drug concentration (C_max) was (22.88±3.11) μg·mL^-1 and (19.77±1.82) μg·mL^-1; the apparent distribution volume (Vd/F) was (2.39±0.81) L·kg^-1 and (2.44±0.46) L·kg^-1; the total body clearance (Cl_B/F) was (0.64±0.11) L·h^-1·kg^-1 and (0.63±0.08) L·h^-1·kg^-1; the area under the drug concentration-time curve (AUC_last) was (47.28±7.87) μg·mL^-1·h and (48.11±6.62) μg·mL^-1·h, respectively. The pharmacokinetic parameters of florfenicol in healthy ducks and infected ducks were analyzed statistically. The results showed that there was no significant difference between the other parameters except C_max (P<0.05).【Conclusion】The peak drug concentration (C_max) in infected ducks was significantly lower (P<0.05) than that in healthy ducks. There was no significant difference between the other pharmacokinetic parameters. The characteristics of rapid absorption, high plasma concentration, wide distribution and faster elimination were showed following im florfenicol injection with a single dosage of 30 mg·kg^-1 body weight in healthy and infected ducks.

Key words: florfenico1, Riemerella anatipestifer, pharmacokinetics , thigh infection, ducks