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

Abstract

Summary 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 μg/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 μug/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.

Establishing bioequivalence of veterinary premixes (Type A medicated articles)

“…phenylbutazone and meclofenamate, in vitro binding to hay and pony nuts was high (>98%) and binding to digesta in vivo was also demonstrated (Lees et al, 1988). In other in vivo studies it was shown that binding to feed and digesta influenced the pattern of absorption of phenylbutazone and flunixin and was postulated to be the cause of: (i) delayed absorption; and (ii) two or more peaks in the plasma concentration-time profiles (Maitho et al, 1986;Welsh et al, 1992).…”

“…In other in vivo studies it was shown that binding to feed and digesta influenced the pattern of absorption of phenylbutazone and flunixin and was postulated to be the cause of: (i) delayed absorption; and (ii) two or more peaks in the plasma concentration‐time profiles (Maitho et al. , 1986; Welsh et al. , 1992).…”

Palatability of flunixin and pharmacokinetics when administered to sheep through feed

“…Horses that had ad libitum access to hay following the oral administration of 238 flunixin had a slower absorption of flunixin and a lower Cmax (Welsh et al 1992). Although 239 concentrations of flunixin in plasma were maintained for longer when animals had access to food 240 compared with when they were fasted (Welsh et al 1992). The AUC was not significantly 241 different between fasted and non-fasted animals with suggesting that the overall concentration of 242 flunixin absorbed is not affected by fasting.…”

“…It is probable that our higher AUC was due to the 232 higher dose rate used in our study. 233 The pharmacokinetics of orally administered flunixin has been studied in goats (Königsson et al 234 2003), horses (Pellegrini-Masini et al 2004;Welsh et al 1992) and cattle (Odensvik 1995). 235 Following oral administration in the absence of feed in these species, flunixin is absorbed rapidly 236 and concentrations can still be detected up to 30 h after administration (Königsson et al 2003; 237 Odensvik 1995).…”

“…235 Following oral administration in the absence of feed in these species, flunixin is absorbed rapidly 236 and concentrations can still be detected up to 30 h after administration (Königsson et al 2003; 237 Odensvik 1995). Horses that had ad libitum access to hay following the oral administration of 238 flunixin had a slower absorption of flunixin and a lower Cmax (Welsh et al 1992). Although 239 concentrations of flunixin in plasma were maintained for longer when animals had access to food 240 compared with when they were fasted (Welsh et al 1992).…”