Plasma disposition kinetics of albendazole metabolites in pigs fed different diets

The influence of diet on the disposition kinetics of albendazole (ABZ) and its metabolites in pigs was investigated. ABZ was administered orally at 10 mg kg-1 to pigs fed either a commercially produced 35 per cent protein/grain concentrate diet (concentrate group), a whey-based diet supplemented with corn grain (whey/grain group) or grazed on pasture (pasture group). Blood samples were taken serially for 96 hours and plasma was analysed by high performance liquid chromatography (HPLC) for ABZ, ABZ sulphoxide (ABZSO), ABZ sulphone (ABZSO2) and amino-ABZSO2 (NH2ABZSO2). ABZ was not detected in plasma at any time after the treatment, and ABZSO and ABZSO2 were the main metabolites detected between 0.5 and 30 to 48 hours after treatment in all the experimental animals. Low concentrations of the NH2ABZSO2 metabolite were found in plasma between 18 and 36 hours after the administration of ABZ to all the groups of pigs. The pharmacokinetic behaviour of the ABZ metabolites in pigs fed either the concentrate of the whey/concentrate diet was substantially different from that observed in pigs grazing on pasture. The peak concentration (C(max)) and areas under the concentration-time curves (AUC) for ABZSO and ABZSO2 were significantly higher (P < 0.01) in the pigs fed on pasture, and were correlated with significantly longer elimination half-lives and mean residence times for both metabolites.