Antiarrhythmic and hemodynamic effects of tropisetron in anesthetized rabbits.

Tropisetron (ICS 205-930) is a novel drug that blocks serotonin (5-HT 3 ) receptors and, at higher concentrations, potassium channels. Programmed electrical stimulation (PES) and tracer microspheres were used to investigate antiarrhythmic, systemic, and regional hemodynamic effects in anesthetized rabbits. Tropisetron (0.3, 1, and 3 mg/kg intravenously, i.v.) dose-dependently increased the effective refractory period (ERP) to a first and similarly to a second extrastimulus. The arrhythmias elicited by PES with one and two extrastimuli were suppressed dose dependently. The same doses and a higher dose (6 mg/kg i.v.) were tested for systemic, especially cardiodepressant, and regional hemodynamic activity in a second series of experiments