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

Ibopamine (SB-7505), the 3,4-diisobutyrylester of N-methyldopamine (epinine), was rapidly hydrolyzed to epinine by plasma esterases of rat as well as of other animal species and man. Ibopamine was rapidly and extensively metabolized after oral administration to rat. Plasma levels of free epinine peaked at 30-60 min from the administration; conjugated epinine was present in larger amount, with a maximum at 3 h. Both free and conjugated epinine were still detectable at 6 h, but not at 24 h. Epinine 4-O-glucuronide, 4-hydroxy-3-methoxyphenylacetic acid and 3,4-dihydroxyphenylacetic acid appeared as main urinary metabolites; epinine 3-O-sulphate, epinine 3-O-methylether and its glucuronide, and trace amounts of epinine 4-O-sulphate were also detected.