Effects of dotarizine on peripheral and pulmonary circulation and cardiac dynamics in dogs.

The cardiovascular effects of dotarizine in 10-min intravenous infusions were studied in thiopental-anesthetized dogs. The effects of dotarizine 0.024 mg/kg/min almost paralleled those of saline controls; 0.079 mg/kg/min dotarizine significantly raised the stroke index and ejection fraction, and, at a rate of 0.25 mg/kg/min, further effects appeared and were dose-dependent. Dotarizine produced arterial dilation in both systemic and pulmonary circulation: the total peripheral resistance dropped, and femoral artery flow rose; aortic and pulmonary artery mean and diastolic pressures declined, and systolic pressures remained almost stable. A trend of bradycardia and pulmonary artery pressure reduction persisted for 30 min. As compared with the reduced total peripheral resistance, aortic pressure fell only moderately because of rising cardiac output due to a higher ejection fraction and stroke volume. Cardiac preload tended to decline; contractility tended to increase. Cardiac performance remained stable while myocardial oxygen consumption tended to fall, as did the pressure-rate product and the tension time index. Dotarizine exerted direct cardiovascular effects similar to those of the 5-HT2-receptor antagonist ketanserin and, more generally, to calcium channel blockers rather than to alpha-adrenoceptor blockers.