Liquid chromatographic analysis of triamterene and its major metabolite, hydroxytriamterene sulfate, in blood, plasma, and urine

The first rapid and highly sensitive high-performance liquid chromatographic (HPLC) assay for triamterene, hydroxytriamterene, and hydroxytriamterene sulfate is reported. Plasma samples were processed by protein precipitation, while urine was used untreated. Three different solvent systems were used to analyze (a) triamterene in plasma (30% acetonitrile, pH 4.0; internal standard: furosemide; sensitivity limit: 1 ng/mL); (b) hydroxytriamterene and hydroxytriamterene sulfate in plasma (12% acetonitrile, pH 5.5; internal standard: cefamandole; sensitivity limits: 20 and 2 ng/mL, respectively) and (c) triamterene, hydroxytriamterene, and hydroxytriamterene sulfate in urine (13% acetonitrile, pH 5.3; internal standard: hydroflumethiazide; sensitivity limits: 0.04 microgram/mL, 0.5 microgram/mL, and 0.1 microgram/mL, respectively). Fluorescence detection of compounds was performed at 365-nm excitation and 440-nm emission wavelengths. Recovery of triamterene and its metabolites from plasma was complete, and calibration curves were linear. Intraday variation was less than 6% except for the lowest plasma concentration. The assay procedure has already been used in several pharmacokinetic studies.