Effects of betaxolol, a new beta 1 selective blocker, on canine ventricular arrhythmias

Antiarrhythmic effects of a new beta 1 selective adrenoceptor blocker, betaxolol, were examined in comparison with those of atenolol using two canine ventricular arrhythmia models (adrenaline arrhythmia and digitalis arrhythmia). Both betaxolol and atenolol suppressed adrenaline arrhythmia, and the minimum effective plasma concentration of betaxolol for this arrhythmia model was determined to be less than 10 ng/ml. However, on digitalis arrhythmia, both beta blockers were ineffective, even though the high doses used in these experiments, 3 mg/kg for betaxolol and 5 mg/kg for atenolol, showed significant hypotensive effects. The present results suggest that betaxolol and atenolol may be expected to be clinically effective on arrhythmias related to increased sympathetic tone.