Pharmacokinetics of tolfenamic acid in ducks (Anas platyrhynchos domestica) after different administration routes

1. The objective of this research was to compare the pharmacokinetics and bioavailability of tolfenamic acid, analgesic, antipyretic and anti-inflammatory compound, after administration through different routes to Pekin ducks. The investigation was carried out over four time periods using a randomised cross-pharmacokinetic design. 2. Tolfenamic acid was administered to ducks intravenously, intramuscularly, subcutaneously and orally at a dose of 2 mg/kg. Tolfenamic acid analysis was performed using HPLC-UV and pharmacokinetic data were conducted by non-compartmental analysis. 3. The total clearance, volume of distribution at steady state and terminal elimination half‐life after intravenous administration were 0.14 l/h/kg, 0.29 l/kg and 1.80 h, respectively. The peak plasma concentration and bioavailability for intramuscular, subcutaneous and oral administration were 4.59, 3.55 and 2.23 μg/ml and 93.62, 74.30 and 43.43%, respectively. 4. Tolfenamic acid was absorbed rapidly, eliminated quickly and exhibited a small distribution volume in Pekin ducks. Pharmacokinetic parameters, including maximum concentration, area under the plasma concentration–time curve and bioavailability, were found to be different in ducks from other bird species.