Oral triamterene disposition

Earlier studies of triamterene (T) disposition in man have reported hydroxytriamterene (T‐OH) and hydroxytriamterene sulfate (T‐O‐SO 3 H) conjugate to be the major metabolites. We describe T kinetics through use of an HPLC method and confirm that after hydroxylation, T is rapidly converted to T‐O‐SO 3 H. The intermediate T‐OH metabolite could not be detected in urine or plasma. Plasma concentrations of T‐O‐SO 3 H exceeded those of T by sevenfold to 26‐fold, whereas concentrations of that metaboUte in the urine were fourfold to thirteenfold higher than those of the parent. Renal clearance of T was 314.5 ± 121.6 ml/min, exceeding that of the metabolite, which was 206.1 ± 93.6 ml/min. Coadministration of hydrochlorothiazide increased urine flow and urinary pH, but it did not affect renal clearance of the parent drug or the metabolite. T bioavailability from capsules was poorer and more variable than that from a suspension. Hydrochlorothiazide did not influence the bioavailability of T. Clinical Pharmacology and Therapeutics (1985) 38, 306–312; doi: 10.1038/clpt.1985.176