Pharmacological characterization of epinine 3-O-sulphate and 4-O-sulphate

Ibopamine, the diisobutyric ester of N-methyldopamine, is able to increase cardiac output and induce vasodilatation on oral administration. While the pharmacodynamic activity of ibopamine is rather long-lasting, N-methyldopamine, i.e. ibopamine's primary metabolite, can be detected in plasma only for a short time after the administration. We have investigated the pharmacological activity of N-methyldopamine 3-O-sulphate and 4-O-sulphate, since the plasma levels of these conjugated metabolites are higher and last longer than those of N-methyldopamine. These compounds appeared to be devoid of any pharmacodynamic activity both in vivo on the main hemodynamic parameters in dog and on diuresis in rat, and in vitro on cat papillary muscle and rabbit ear artery. Consequently, the duration of ibopamine hemodynamic effects cannot be related to these circulating metabolites, thus other hypotheses should be taken into consideration.