BLOCKADE OF CARDIAC EFFECTS OF ISOPROTERENOL BY STEREOISOMERS OF SOTALOL

The effect of levo- and dextro-rotatory optical isomers of sotatol [4-(2-isopropylamino-1-hydroxyethy1)-methanesulfonanilide; MJ 1999] was investigated on the myocardial stimulant effect of isoproterenol in the isolated supported (blood perfused) dog heart preparation. Intracoronary injection oisoproterenol in doses ranging from 0.0062 to 3.2 μg produced an increase in heart rate, left ventricular force (CF), left ventricular systolic pressure (LVSP), myocardial oxygen consumption (MVO2) and a decrease in coronary artery perfusion pressure (CAPP) in a dose-dependent manner. All these cardiac effects of isoproterenoll were competively blocked by 0.25 mg/kg levo-sotalol. Dextro-sotalol has a minimal effect in doses up to 2 mg/kg. Levo-sotalol itself slightly depressed the heart rate, CF, LVSP and MVO3 in these experiments. However, it produced an increase in the CAPP, and a slight decrease in 88Rb clearance by the heart. It is concluded that levo-sotalol is the active isomer for the beta-adrenoreceptor blocking activity in the heart. © 1969.