Extraordinary cardiac effects of 16-epi-gitoxin in comparison to ouabain in cats and dogs.

The contractility and arrhythmogenic effects of 16-epi-gitoxin and ouabain were studied in dogs. ECG alteration-producing and lethal doses of both glycosides were determined in cats. 16-Epi-gitoxin was found to be a glycoside with rapid onset and short duration of action. In case of equal contractile increment ouabain caused a higher percentage of rhythm disturbances in dogs than 16-epi-gitoxin. This finding corresponds to that in cats, in which ECG changes (QRS complex prolongation) occurred after ouabain at a lower percentage of the lethal dose than after 16-epi-gitoxin. Apart from its slight arrhythmogenic effects, 16-epi-gitoxin may be compared with acetylstrophanthidin.