Determination of isoetharine in plasma by reversed-phase chromatography with amperometric detection.

A reversed-phase liquid chromatographic method for the determination of isoetharine in blood plasma, utilizing amperometric detection, is described. Plasma samples were extracted utilizing an ion-pair reagent, di-(2-ethylhexyl)phosphoric acid, to concentrate the catecholamine. Only minor differences were observed in the relative bioavailability of isoetharine hydrochloride and isoetharine mesylate after oral administration to rats. Observed plasma levels, at 1 hr after oral medication, were highly variable in dose-ranging studies at doses of 800-2500 mg/kg/day for 2 weeks.