LACK OF DESENSITIZATION OF ALPHA-ADRENOCEPTOR AND BETA-ADRENOCEPTOR FUNCTION DURING CHRONIC TREATMENT OF HEALTHY-VOLUNTEERS WITH IBOPAMINE, AND 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 x 1 00 mg/day p. o.), respectively its active metabolite epinine, would desensitize lymphocyte beta2- or platelet alpha2-adrenoceptors, or alpha1- and beta-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 alpha- or beta-adrenoceptor parameters measured. Since in man in general long-term administration of alpha- and beta-adrenoceptor agonists desensitizes alpha- and beta-adrenoceptors, the lack of any alpha- and beta-adrenoceptor desensitizing effect of ibopamine suggests that, in the dose employed (3 x 100 mg per day), ibopamine does not exert alpha- or beta-adrenoceptor agonistic effect in humans.