Lack of desensitization of α-and β-adrenoceptor function during chronic treatment of healthy volunteers with ibopamine, an orally active dopamine receptor agonist

In 18 healthy volunteers, in a double-blind placebo-controlled study, we investigated of whether 14 days treatment with a therapeutic dose of ibopamine (3×100 mg/day p.o.), respectively its active metabolite epinine, would desensitize lymphocyte β2- or platelet α2-adrenoceptors, or α1- and β-adrenoceptor mediated (phenylephrine-and isoprenaline infusions, respectively), changes in systolic and diastolic blood pressure and heart rate. Ibopamine-treatment, which resulted in peak plasma epinine concentrations of 4-5 nmol·l-1, neither affected resting heart rate or blood pressure, nor any of the α- or β-adrenoceptor parameters measured. Since in man in general long-term administration of α- and β-adrenoceptor agonists desensitizes α- and β-adrenoceptors, the lack of any α- and β-adrenoceptor desensitizing effect of ibopamine suggests that, in the dose employed (3×100 mg per day), ibopamine does not exert α- or β-adrenoceptor agonistic effect in humans.

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