Pharmacokinetics of Tolfenamic Acid Administered Orally and Intravenously at Different Doses in Pekin Ducks ().

This study aimed to examine the pharmacokinetic changes in tolfenamic acid administered intravenously and orally to ducks at different doses (2, 4, and 8 mg/kg). Furthermore, the binding ratio to plasma proteins was assessed utilizing the ultrafiltration method. Eighteen male Pekin ducks were randomly assigned to three dosage groups (2, 4, and 8 mg/kg), with each group undergoing a trial in two phases: intravenous (IV) and oral administration. The sample was analyzed using an approved HPLC-UV method. A non-compartmental analysis was utilized to evaluate the pharmacokinetic data. For 2 mg/kg IV injection, the area under the curve from zero to infinity (AUC), total clearance (Cl), volume of distribution at steady state (V), and elimination half-life (t) were 13.03 h*µg/mL, 0.15 L/h/kg, 0.30 L/kg, and 1.72 h, respectively. Following oral administration at a dose of 2 mg/kg, the AUC, peak plasma concentration (C), and bioavailability were 6.32 h*µg/mL, 2.25 µg/mL, and 48.52%, respectively. The t was extended, C and AUC elevated, T shortened, and Cl decreased in a dose-dependent manner. No dose-related change was observed in V and bioavailability. In ducks, tolfenamic acid's plasma protein binding was 99.74%, unaffected by concentration. These results may contribute to the application of tolfenamic acid in ducks at different doses, but dose-related changes in therapeutic efficacy should also be demonstrated.