Antiarrhythmic Effect of Oxprenolol on Halothane-Epinephrine and Coronary Ligation Induced Ventricular Arrhythmias in Beagle Dogs

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Abstract
Antiarrhythmic effects of oxprenolol, a .beta.-blocker, were studied quantitatively on arrhythmias produced by epinephrine during halothane anesthesia and by 2-stage coronary ligation, and were compared to those of other .beta.-blockers, propranolol and Ko 1400 [I-[(tert-butylaminopropanolo)oxy]-2-ethynylmethoxy benzene] which were reported. Though oxprenolol has potent .beta.-blocking activity, the antiarrhythmic effect on halothane-epinephrine arrhythmia was significantly weaker than those of propranolol and Ko 1400. The effective dose of oxprenolol was 60 .+-. 18 .mu.g/kg (mean .+-. SE, N = 6), which is in the range of the so-called .beta.-adrenergic blocking dose. The weaker antiarrhythmic effect of oxprenolol as compared to propranolol and Ko 1400 is probably due to the intrinsic positive chronotropic effect, which is most clearly observed in oxprenolol as compared to the other 2 drugs. As for 2-stage coronary ligation arrhythmia, oxprenolol suppressed only that observed 48 h after coronary ligation using higher doses (5-10 mg/kg). Other .beta.-blockers also showed similar effects. Because of the high doses necessary for the antiarrhythmic effects on the coronary ligation arrhythmia, the mechanism for suppressing the arrhythmia is probably due to the local anesthetic action of the .beta.-blockers.