Uptake of Fenbendazole by Grazing Sheep with Access to Feed-Blocks Containing Fenbendazole

The concentrations of fenbendazole and oxfendazole, its principal metabolite, were measured in the plasma of sheep grazing marginal upland pasture with access to high-energy feed-blocks medicated with fenbendazole. Only one of 18 sheep appeared to consume an inadequate dose of fenbendazole. It is concluded that this method of drug administration can confer certain advantages over conventional methods of administration.