Absence of proarrhythmic effects of ibopamine in patients with congestive heart failure.

Ibopamine, the di-isobutyric ester of N-methyldopamine, is an orally effective dopamine-related drug. Ibopamine acts mainly through the stimulation of beta 1- and beta 2-adrenergic and dopaminic DA1 and DA2 receptors. Cardiac beta 1 activation may facilitate the occurrence of arrhythmias, by reducing the mean refractory period. The aim of this multicenter investigation was to ascertain whether the administration of ibopamine can induce any rhythm disorder or increase pre-existing arrhythmias. In the first part of the investigation, after a washout period 20 patients were treated randomly under double-blind conditions with ibopamine (100 mg t.i.d.) or placebo for 7 days. In the second part of the study, 25 patients were treated with placebo for 7 days, and then with ibopamine (100 mg t.i.d. and 200 mg t.i.d.) for another two 7-day periods. The results did not show any increase in arrhythmias during the two ibopamine periods, in comparison with the data collected under placebo treatment. Ibopamine did not affect heart rate and blood pressure. The number of SVPBs and VPBs decreased considerably in several patients and also the Lown classification improved after ibopamine treatment, even after the 200 mg t.i.d. dose. It can be concluded that ibopamine does not seem to elicit any significant proarrhythmic property.