The atrioventricular block was produced in dogs 24 hours after the occlusion of the left descending coronary artery by formalin injection into the atrioventricular node or the bundle of His. The intensity and duration of the ectopic foci inhibition produced by ethmozine and by its diethylamine analogue (ethmozine DAA) were compared. It was shown that intravenous infusion of 3 mg/kg ethmozine reduced the frequency of the ectopic ventricular excitations by 28% (n = 6), 0.5 mg/kg ethmozine DAA - by 46% (n = 7), and 1 mg/kg ethmozine DAA - by 78% (n = 8). In 50% of the animals 1 mg/kg ethmozine DAA completely suppressed the ectopic activity. Duration of the drugs action was determined by the time necessary for the attainment of 50% of the maximal effect in the inhibition of ectopic exitation frequency (for 3 mg/kg ethmozine it was 32.7 +/- 2.5 min, for 0.5 mg/kg ethmozine DAA - 5.1 +/- 7.2 min, and for 1 mg/kg ethomozine DAA - 55.0 +/- 9.8 min). The results obtained suggest that the ethmozine DAA action is more intensive and of longer duration than ethmozine, and effective at the late stage of experimental myocardial infarction.