Pharmacokinetics of florfenicol and thiamphenicol in ducks

The pharmacokinetics of florfenicol (FF) and thiamphenicol (TP) after single intravenous (IV) and oral (PO) administration was investigated in Mulard ducks. Both antibiotics were administered at a dose of 30 mg/kg body weight, and their concentrations in plasma samples were assayed using high-performance liquid chromatography with ultraviolet detection. Pharmacokinetic parameters were calculated using a noncompartmental method. After IV administration, significant differences were found for the mean residence time (2.25 +/- 0.21 hr vs. 2.83 +/- 0.50 hr for FF and TP, respectively) and the general half-life (1.56 +/- 0.15 hr vs. 1.96 +/- 0.35 hr for FF and TP, respectively) indicating slightly slower elimination of TP as compared to FF. The clearance, however, was comparable (0.30 +/- 0.07 L/hr/kg for FF and 0.26 +/- 0.04 L/hr/kg for TP). The mean volume of distribution was below 0.7 L/kg for both drugs. Pharmacokinetics after PO administration was very similar for FF and TP suggesting minor clinical importance of the differences found in the IV study. Both antimicrobials showed rapid absorption and bioavailability of more than 70% indicating that PO route should be an efficient method of FF and TP administration to ducks under field conditions.