Plasma and urinary levels of triamterene and certain metabolites after oral administration to man.

The plasma and urinary levels of triamterene and two metabolites were measured using a specific method of analysis. Urinary excretion was completed after 48 h, which permitted a rough estimate of its half-life as longer than two hours. The areas under the curve were 672.5 +/- 160.3 and 1.311.3 +/- 399.1 micrograms/ml X h after the triamterene 150 mg and 300 mg p.o., respectively and correspondingly 4.2 +/- 1.4% and 3.7 +/- 0.6% of the dose were excreted as unchanged drug. The principal metabolite of triamterene found was the sulfate conjugate. The area under the curve of this metabolite amounted to 6.672 +/- 2.120 and 11.941 +/- 5.005 micrograms/ml X h after the of 150 mg and 300 mg triamterene doses, respectively. The urinary excretion of the metabolite varied between 25.0 +/- 4.0% and 17.5 +/- 3.5% of the dose after either dose. In healthy subjects an effect on sodium excretion was observed after a dose of 150 mg, whereas the potassium-retaining effect was observed only after the dose of 300 mg.