Triamterene and renal stone formation.

We investigated the influence of triamterene (TA), and its metabolites parahydroxytriamterene (PHTA), and parahydroxytriamterene sulfate (PHTAS) on the nucleation and crystal growth of calcium oxalate monohydrate (COM), in supersaturated solution at 37C using a new constant composition technique. The spontaneous precipitation of COM is preceded by induction periods which decrease with increasing supersaturation. The addition of the triamterene seed materials substantially reduces there delay periods and induces the crystal growth of COM. Specific surface area and scanning electron microscopic results indicate that the seed materials act as sources for the heterogeneous nucleation of COM. In addition, the surface of the more crystalline PHTAS appears to offer sites from which COM crystals can develop as well formed rosettes. This evidence suggests that in addition to triamterene renal stone formation, TA and its metabolites may catalyze the precipitation of other stone forming minerals with which urines may be supersaturated.