Analysis of epinine and its metabolites in man after oral administration of its pro-drug ibopamine using high-performance liquid chromatography with electrochemical detection.

Ibopamine (N-methyldopamine O,O'-diisobutyrol ester, hydrochloride) is an ester prodrug of epinine. Epinine is a cardiovascular agent used in congestive heart failure because of its dopaminergic and adrenoreceptor agonist properties. Quantitative analytical methods, using high-performance liquid chromatography coupled with electrochemical detection, were developed for the determination of epinine and its known metabolites in biological media. Epinine was extracted from human plasma and urine via an alumina adsorption procedure; this procedure was also used to estimate epinine conjugates after prior enzymatic hydrolysis. Penicillamine was added to the incubation mixture to inhibit isoquinoline production. Urinary dihydroxyphenylacetic acid levels were obtained using the same alumina adsorption procedure, while a separate analytical procedure utilizing a direct high-performance liquid chromatographic analysis of samples was developed for homovanillic acid and its conjugates. Coefficients of variation for all the assays were below 8%. These methods were used to study the pharmacokinetics and metabolic fate of epinine after oral administration of ibopamine to healthy volunteers.