Cardiovascular pharmacology of bumepidil, a new synthetic vasoactive compound for coronary circulation

Intravenously administered 8-tert.-butyl-7,8-dihydro-5-methyl-6H-pyrrolo[3,2-e]triazolo[1,5-alpyrimidine (bumepidil, CS-611) increased the coronary sinus outflow as well as intramyocardial flows in both subendocardial and subepicardial layers in the anesthetized dog and also the increase in the coronary arterial inflow was observed with short onset time, within 10 min when given orally to the conscious dog, and time for maximum effect is also short, i.e., 20 min after the oral administration. In the anesthetized rabbit flow-increase in the brain by CS-611 was next to the coronary, followed by the stomach and small intestines while there was no organ which showed a decreased flow. In the anesthetized open-chest dog cardiac output was increased by CS-611 while myocardial oxygen consumption was little affected. In addition, CS-611 exerted antiarrhythmic action on ventricular ectopics induced by coronary ligation of the conscious dog. A correlation between the increase in myocardial flow by CS-611 in the intact heart and the antiarrhythmic action in the coronary-lighted heart still remains to be studied further.