Pharmacokinetics of firocoxib after administration of multiple consecutive daily doses to horses

Objective—To determine pharmacokinetic parameters and variables, firocoxib concentrations in urine and plasma, urine-to-plasma ratios, and the urine depletion profile of firocoxib and to evaluate whether the pharmacokinetic behavior of firocoxib was governed by linear processes after multiple doses of firocoxib were administered IV and orally. Animals—6 healthy female horses (5 Paint horses and 1 Quarter Horse) in experiment 1 and 12 healthy male and female horses in experiment 2. Procedures—In experiment 1, 6 horses were orally administered firocoxib paste once daily for 12 consecutive days, and plasma and urine samples were obtained and analyzed. In a second experiment, 12 horses received IV injections of firocoxib solution once daily for 9 consecutive days, and plasma was obtained and analyzed. Results—Mean ± SD clearance and steady-state volume of distribution of firocoxib were 40.5 ± 14.7 mL/h/kg and 2.3 ± 0.7 L/kg, respectively. Mean half-life was 44.2 ± 21.6 hours and 36.5 ± 9.5 hours for IV and or...