The true composition of kidney stones passed during triamterene therapy

The potassium-sparing agent triamterene and its metabolites have been identified as components of kidney stones passed by patients receiving that drug. We have analyzed 66 such kidney stones by use of quantitative thin-layer chromatography. The stones contained not only the unchanged triamterene but also significant amounts of an intermediate metabolite, hydroxytriamterene, and large amounts of the sulfate ester of hydroxytriamterene. Of the stones 49 per cent contained less than 5 per cent triamterene and its metabolites, and no stone comprised 100 per cent triamterene-derived material. Of all the triamterene-related material unchanged triamterene dominated. However, the relative fractions of triamterene and hydroxytriamterene in the kidney stones exceeded the relative fractions of these 2 components in the urine.