Pharmacokinetics of indomethacin after intraruminal administration to sheep.

The pharmacokinetics of indomethacin (7 mg/kg) was determined in six adult sheep after intraruminal administration. The plasma concentration-time curves showed different patterns for each sheep, depending on the physiological state of the gastrointestinal tract, where absorption took place, and possible enterohepatic and saliva recycling. Indomethacin was irregularly and poorly absorbed from the rumen after intraruminal administration to sheep. Plasma concentrations barely rose to the lower therapeutic margin and mean bioavailability was 38.25 +/- 15.98%. The elimination phase was slow (beta = 0.015 +/- 0.010 h-1) and the half-life was long (t1/2 beta = 56.52 +/- 31.21 h). The mean residence time was 20.01 +/- 6.92 h.