Capillary electrophoretic detection of metabolites in the urine of patients receiving hypoglycemic drug therapy

Micellar electrokinetic chromatography (MEKC) in tandem with diode array detection (DAD) has been exploited as an analytical method for the separation and detection of sulfonylurea drugs. The ultimate goal is the development of an assay to detect these drugs or their metabolites in urine as a means of diagnosing sulfonylurea drug abuse. Using a spearation buffer consisting of 5 mM borate/5 mM phosphate/75 mM sodium cholate, separation of both the second and third generation sulfonylurea drugs can be achieved. The characteristic absorbance spectra associated with each of the third generation drugs, glipizide and glyburide, allow for their identification in mixtures. Coinjection of glyburide, its primary metabolite, hydroxy glyburide, and glipizide demonstrated that the metabolite was resolved from the parent drug but shared its absorbance spectral properties. MEKC analysis of a series of solid phase-extracted urine samples from patients prescribed glipizide or glyburide, as well as from control patients not ingesting the drug, showed that the parent compounds were difficult to detect in the urine. However, the use of DAD allowed for detection of metabolites in the urine of these patients. With glyburide patients, only primary metabolites were detected, while urine from patients on glipizide showed a series of peaks whose absorbance spectra was consistent with the presence of both primary and secondary metabolites. In addition, the intensity of the metabolite peaks corresponded reasonably well with the respective dose and in vivo time interval associated with the urine collection. This study shows that MEKC with DAD has potential for further exploration as a clinical assay for detecting surreptitious abuse of sulfonylurea drugs.