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

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_0-∞), total clearance (Cl_T), volume of distribution at steady state (V_dss), and elimination half-life (t_1/2ʎz) 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_0-∞, peak plasma concentration (C_max), and bioavailability were 6.32 h*µg/mL, 2.25 µg/mL, and 48.52%, respectively. The t_1/2ʎz was extended, C_max and AUC_0-∞ elevated, T_max shortened, and Cl_T decreased in a dose-dependent manner. No dose-related change was observed in V_dss 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.