Triamterene urolithiasis: solubility, pk, effect on crystal formation, and matrix binding of triamterene and its metabolites.

The commonly used diuretic Tri and its metabolites have been identified recently as major components of some kidney stones. We have carried out basic physical chemical studies to determine the mechanism of Tri incorporation into kidney stones. The solubility and pK of Tri and its major metabolites, Tri-OH and the Tri-So4, have been determined at 37 C in 0.15 M NaCl. The effect of Tri and its metabolites on crystal formation has been measured in the calcium oxalate monohydrate, hydroxyapatite, and uric acid crystal systems. Tri and its metabolites do not promote crystal nucleation, growth, or aggregation in any of these crystal systems and are not incorporated as these crystals form. We can demonstrate binding of Tri and its metabolites to the protein matrix isolated from kidney stones. These data suggest that Tri and its metabolites to the protein matrix isolated from kidney stones. These data suggest that Tri and its metabolites do not promote the formation of kidney stones but rather become incorporated into existing stones or stone nidi by binding to the protein matrix found in all kidney stones.