Flunixin meglumine: Quantitative determination in and effects on composition of equine inflammatory exudate

The non-steroidal anti-inflammatory drug flunixin meglumine was administered intravenously at the therapeutic dose level (1·1 mg/kg) to six ponies in a two-part cross-over study. Concentrations of the drug were measured up to 48 h in plasma and in inflammatory exudate harvested from subcutaneously implanted tissue cages and stimulated with carrageenin. The plasma: exudate concentration ratio decreased from 3 to 12 h after which time drug concentration fell to below detection limits in most samples. The persistence of flunixin in exudate may help to explain why its clinical effects in horses may persist for more than 12 h. Total protein levels in inflammatory exudates were significantly elevated (P < 0·05) in both treated and non-treated ponies at 12 and 24 h. This study demonstrated an inhibitory effect of the drug on exudate levels of prostaglandin E2, thromboxane B2 and the metabolite of prostacyclin, 6-keto- prostaglandin F1α, which suggested that the anti-inflammatory actions of flunixin are linked to the inhibition of cyclo-oxygenase derived eicosanoids.