“Both diphenylhydantoin sodium and procaine amide can suppress digitalis arrhythmias due to enhanced automaticity, but procaine amide may promote “re-entry” arrhythmias by potentiating the intraventricular conduction defect caused by the glycoside.”
“In addition, diphenylhydantoin sodium appears to antagonize the action of digitalis on the A-V node, while procaine amide increases the digitalis-induced A-V block.”