Antiarrhythmic action of a new beta-adrenergic blocking agent, 6-(2-hydroxy-3-isopropylaminopropyloxy)-benzothiazole succinate (KF-577), compared with that of propranolol.

The antiarrhythmic activity of a new beta-adrenergic blocking agent, 6-(2-hydroxy-3-isopropylaminopropyloxy)-benzothiazole succinate (KF-577), was compared with that of propranolol. KF-577 antagonized ouabain-induced arrhythmias in normal and bilaterally vagotomized guinea pigs; its antagonistic activity was equal to that of propranolol. Reserpinization greatly reduced ouabain intoxication and neither of the two beta-blockers produced further reduction. Aconitine-induced arrhythmias in rats were not antagonized by the two agents. In intact guinea pigs, the reduction of ouabain intoxication by both beta-blockers could not exceed that produced by simulataneous infusion of KCl, and vice versa. In isolated guinea pig atria, propranolol was about 10 times more effective than KF-577 in reducing the ouabain intoxication. The antiaarhythmic activity of KF-577 paralleled its beta-blocking activity in the isolated preparations but not in the intact animals.