Pharmacokinetic behaviour of fenbendazole in buffalo and cattle.

Concentrations of fenbendazole and of drug metabolites in plasma were measured in buffalo and cross-bred cattle after single intraruminal administration at two different doses. Plasma concentrations of the parent compound fenbendazole and the two metabolites, viz. oxfendazole and fenbendazole sulfone, were much lower in buffalo compared with cattle, at a dose of 7.5 mg/kg body weight as indicated by lower area under concentration curve and concentration maximum. At a dose of 15 mg/kg body weight there were corresponding increases in plasma metabolite concentrations in cattle. However, buffaloes did not show a similar corresponding increase.