Ibopamine, an orally active dopamine-like drug: metabolism and pharmacokinetics in dogs.

Ibopamine (SB-7505), the 3,4-diisobutyryl ester of N-methyldopamine (epinine), exerts, on oral administration, cardiovascular effects similar to those of intravenously infused dopamine. Plasma levels and urinary excretion of metabolites were investigated in dogs after oral administration of 4 mg/kg of ibopamine hydrochloride. Epinine, which was readily formed from ibopamine by esterases hydrolysis, was present in plasma in free and sulphate-conjugated form. The urinary metabolites after 6 h from the administration amounted to 62% of the dose, as a sum of 37% of epinine 3-O-sulphate, and 15 and 10% of 4-hydroxy-3-methoxyphenylacetic acid and 3,4-dihydroxyphenylacetic acid, respectively, both in free and conjugated form. When the main metabolite, epinine 3-O-sulphate, was administered intravenously it appeared to be excreted in urine without being deconjugated to any detectable extent, while it appeared to be partially deconjugated on oral administration.