Electrophysiology and pharmacology of cardiac arrhythmias. VIII. Cardiac effects of diphenylhydantoin. B.

DPH is highly effective against both atrial and ventricular arrhythmias resulting from digitalis toxicity and should be considered one of the primary antiarrhythmic drugs in this clinical situation. Clinical studies have indicated that DPH, for the most part, is effective against atrial arrhythmias and not markedly effective against ventricular arrhythmias associated with acute or chronic cardiac disease. For the latter ventricular arrhythmias, DPH is usually considered only after other antiarrhythmic drug therapy has failed. Studies on the mechanisms responsible for the antiarrhythmic effects of DPH are, as yet, inconclusive, There is good evidence that its actions differ from those of the commonly used drugs with local anesthetic effects. The extent to which it exerts direct effects on the heart which are therapeutically relevant remains to be demonstrated; further, there is solid evidence that its effects on the central nervous system may be of prime importance in its antiarrhythmic efficacy.