Effect of diphenylhydantoin sodium (dilantin) on myocardial A-V potassium difference

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Abstract
The effects of digitalis and diphenylhydantoin on myocardial ion fluxes was studied. Toxic doses of digitalis caused a decrease in arterial-coronary sinus K difference indicating a loss of K from the myocardium. Diphenylhydantoin administration converted the digitalis-induced arrhythmia in all cases and this was always accompanied by a reversion of the digitalis-induced myocardial K loss. When diphenylhydantoin was given to un-digitalized dogs, no change in myocardial A-V K difference was observed. Neither digitalis nor diphenylhydantoin had any consistent effect on Na or pH values. There is suggestive evidence that digitalis causes myocardial K efflux by inhibiting the cation active transport system across the cell membrane and that this may be related to its toxic effects. In correcting digitalis toxicity, the antiarrhythmic effect of diphenylhydantoin may be due to its reversal of these processes.