Netobimin and
albendazole were administered to 3-month-old lambs with moderate
infections of Nematodirus battus and to comparable parasite-naive lambs.
Albendazole sulphoxide and
albendazole sulphone concentrations were determined in the plasma of all lambs at frequent intervals
after treatment. Both
anthelmintic preparations were 100% effective in reducing nematode faecal egg output in the lambs. There were no significant differences in the concentrations of the
sulphoxide or sulphone metabolites in parasitized compared with non-parasitized lambs given the same parent
anthelmintic. The parasite-naive lambs were subsequently weaned and maintained indoors in conditions designed to preclude nematode
parasite infection until they were 9 months old.
Netobimin and
albendazole were administered again and the plasma profiles of the
albendazole sulphoxide and
albendazole sulphone metabolites determined. There were no significant differences in the plasma distribution of these metabolites with age of the lambs. The area under the plasma concentration time curve, mean resident time and apparent half-life of the
albendazole sulphoxide metabolite was determined following administration of each parent
drug and the clearance of the metabolite/systemic availability of parent
drug was determined as a marker of the amount of
drug available for metabolism. There were no significant differences in pharmacokinetic variables between parasitized and non-parasitized animals nor with the age of the animals.