Influence of feeding schedule on the absorption of orally administered flunixin in the horse

The effects of access to hay and of restricted feeding on the pharmacokinetics of flunixin administered orally to six healthy ponies were compared in a cross-over study. No access to feed for a few hours before and after flunixin administration resulted in rapid absorption with a mean peak plasma concentration of 2.84 +/- 0.28 micrograms/ml attained in an average time of 0.76 +/- 0.18 h, followed by an exponential decline in plasma concentration. A lower peak plasma concentration was obtained when ponies had free access to hay before and after drug dosing. The mean maximum concentration (Cmax) was 1.30 +/- 0.23 micrograms/ml and maximum time (tmax) was prolonged to a mean time of 7.66 +/- 1.74 h. Free access to hay reduced and delayed the peak plasma concentration resulting in two or three separate concentration peaks in some ponies. The mean area under the plasma concentration-time curve was not significantly different for the two feeding regimens.