Pharmacodynamics and pharmacokinetics of carprofen in the horse

The pharmacokinetics and pharmacodynamics of the nonsteroidal anti-inflammatory drug (NSAID) carprofen have been evaluated in 6 horses using a model of acute non-immune inflammation. Following intravenous administration of 0.7 mg racemic carprofen/kg bwt, mean values for pharmacokinetic parameters were 18.1 h (elimination half-life); 0.25 l/kg (volume of distribution, Vd[area]); 58.9 ml/min (clearance); and 57.9 micrograms/ml.h (area under plasma concentration time curve). Mean exudate:plasma concentration ratios exceeded 1.0 at all sampling times between 2 and 48 h. Swelling at the site of acute inflammation was significantly reduced but exudate leucocyte numbers were unchanged. Although carprofen produced moderate suppression of serum thromboxane B2 and exudate prostaglandin E2 synthesis, these effects were not related to carprofen concentrations in plasma or exudate. It was concluded that the anti-oedematous action of carprofen was not attributable to inhibition of cyclo-oxygenase.