Onset of cardiovascular action after oral ibopamine. Early hemodynamic effects of single and repeated doses in patients with idiopathic dilated myocardiopathy

The acute effects of ibopamine (active ingredient of Inopamil), an orally active dopaminergic agent, were invasively evaluated in 16 consecutive patients with idiopathic dilated cardiomyopathy (New York Heart Association Functional Class II and III) Single doses of 100 and 200 mg were administered to 7 and 9 patients, respectively, and two repeated doses of 100 mg were studied in 6 patients. In order to assess the onset of cardiovascular effect, control hemodynamic measurements were repeated 5, 10, 15, 20, 30, 60, 120, and 180 min after ibopamine 200 mg. Both the tested doses of ibopamine increased the mean pulmonary arterial pressure and the mean pulmonary wedge pressure, with a maximal effect 15 min after drug ingestion (+ 47.0 and + 65.4% in the 200 mg group, p less than 0.002). Pulmonary pressures returned to baseline or lower values beyond 60 min. Systemic arterial pressure showed a small transient increase (+ 7.9% in the 200 mg group at 15 min), but fell significantly below baseline after 120 min, a larger decrease occurring in the 100 mg group (p less than 0.05). Ibopamine had a slower but more prolonged effect on cardiac output (increase of up to 32.1% at 60 min) and systemic vascular resistances. Repeated doses (100 mg after an 8-h interval) elicited comparable cardiovascular effects. Oral ibopamine caused a significant increase in mean pulmonary arterial and capillary pressures as early as 5 min after drug ingestion, before cardiac output and peripheral vascular resistances were affected. A biphasic hemodynamic response was also observed after single and repeated low (100 mg) doses of ibopamine.