Effect of dose on the intravenous pharmacokinetics of tolfenamic acid in goats.

The objective of this study was to determine the pharmacokinetics of tolfenamic acid (TA) following intravenous (IV) administration at doses of 2 and 4 mg/kg in goats. In this study, six healthy goats were used. TA was administered intravenously to each goat at 2 and 4 mg/kg doses in a cross-over pharmacokinetic design with a 15-day washout period. Plasma concentrations of TA were analyzed using the high performance liquid chromatography with ultraviolet detector, and pharmacokinetic parameters were assigned by noncompartmental analysis. Following IV administration at dose of 2 mg/kg, area under the concentration-time curve (AUC0-∞ ), elimination half-life (t1/2ʎz ), total clearance (ClT ) and volume of distribution at steady state (Vdss ) were 6.64 ± 0.81 hr* µg/ml, 1.57 ± 0.14 hr, 0.30 ± 0.04 L h-1  kg-1 and 0.40 ± 0.05 L/kg, respectively. After the administration of TA at a dose of 4 mg/kg showed prolonged t1/2ʎz , increased dose-normalized AUC0-∞ , and decreased ClT . In goats, TA at 4 mg/kg dose can be administered wider dose intervals compared to the 2 mg/kg dose. However, further studies are needed to determine the effect of different doses on the clinical efficacy of TA in goats.