Liquid chromatography with electrochemical detection for monitoring mebendazole and hydroxymebendazole in echinococcosis patients.

A sensitive method is described for the simultaneous determination of mebendazole and hydroxymebendazole using flubendazole as an internal standard. The analytes were isolated with a single chloroform extraction from 1.0 ml of alkalinized plasma or cyst liquid samples. Separation and quantitation were performed with high-performance liquid chromatography with electrochemical detection. The limit of detection for mebendazole and hydroxymebendazole was approximately 5 and 2.5 ng/ml, respectively. The accuracy of the method was confirmed for mebendazole by a good correlation with an existing radioimmunoassay method. The method was applied for monitoring mebendazole therapy in echinococcosis patients. The results presented support the necessity of such monitoring, as most of the observed peak plasma concentrations did not reach the level regarded as minimal for therapeutic effect.