[Drug induced nephrolithiasis: observation of an oxalate and hydroxylated triamterene stone (author's transl)].

A 54-year old man who had been taking triamterene (150 mg daily) over a period of 8 months, passed a 3 mm stone partly coated with mustard-colored substance. Metabolic evaluation showed only mild-hyperoxaluria. Through IR spectrography after microdissection, thin-layer chromatography, UV light examination, and mass spectrometry, the stone if found to consist of 70% whewellite, 5% protein, 5% carbapatite and 20% triamterene and hydroxylated triamterene, and perhaps also the sulfate conjugate of this metabolite. In spite of the few number of observations (two cases have been reported previously), triamterene seems likely to induce stone formation, both alone and associated with urate or oxalate, and triamterene should be used cautiously in patients with a predisposition for nephrolithiasis.