Simultaneous determination of albendazole and its principal metabolites in plasma by normal phase high-performance liquid chromatography.

A sensitive, specific and reproducible high-performance liquid chromatography procedure using normal phase is described for the simultaneous determination of albendazole, albendazole sulphoxide and albendazole sulphone in sheep plasma, with mebendazole as an internal standard. Analysis of plasma requires only 100 mul of sample, which is extracted with ethylacetate and injected directly onto a 5-mum normal phase column, using hexane-ethanol (445:55, v/v) as eluent, with detection at 225 nm. The standard curves in plasma were linear for both albendazole and its metabolites at concentrations from 0.1 to 10 mug/ml. The method has been applied to the determination of plasma levels of albendazole and metabolites during preliminary pharmacokinetic studies in sheep.