Variations in the fate of triamterene

: Triamterene is a pteridine used therapeutically as a diuretic. In order to better understand variations in effect and toxicity of triamterence in individuals, the fate of the drug in man was investigated. Both nonradioactive and 14C-labeled forms of the drug were administered, and specific methods of analysis were used to separate the parent compound from its metabolite. Individual variation in absorption, binding, and elimination was noted. The drug was excreted in bile as well as urine. Rapid and extensive metabolism of the agent occurred after oral and intravenous doses in healthy adult men. The peak plasma levels of the drug after an oral dose (200 mg) were under 0.3 microng/ml, but the concentration of the primary metabolite. (2,4,7-triamino-6-p-hydroxyphenylpteridine) was higher. The urinary excretion of the metabolite was at least three times that of the parent drug.