THE PARTITION AND FATE OF SOLUBLE AND DIGESTA PARTICULATE ASSOCIATED OXFENDAZOLE AND ITS METABOLITES IN THE GASTROINTESTINAL-TRACT OF SHEEP

The disposition of oxfendazole (OFZ) containing a trace of [C-14]OFZ w as examined in the gastrointestinal tract and bloodstream of sheep fit ted with rumen and abomasal cannulae. Within 2 h of intraruminal (IR) administration, OFZ and its metabolites were almost completely associa ted with rumen particulate digesta. The proportion of metabolites in d igesta fluid increased with their passage from the rumen into the abom asum. To determine the fate of C-14-labelled metabolites after distrib ution throughout rumen digesta, the rumen particulate and fluid digest a phases from a donor sheep were separated and each transferred to the rumen of an untreated recipient sheep. The C-14-labelled metabolites which derived from the donor rumen fluid quickly associated with recip ient rumen particulate material. The metabolites were then progressive ly desorbed, as were metabolites which were transferred already associ ated with rumen particulate digesta. Desorption occurred faster in the abomasum than in the rumen. There was no difference in uptake kinetic s between administration routes, indicating rapid equilibrium. Consequ ently the disposition of [C-14]OFZ and its metabolites in the bloodstr eam was similar in each group. It is suggested that the progressive de sorption of particulate associated metabolites is a principal determin ant of the duration of OFZ availability.