Diphenylhydantoin in the Prevention of Recurring Ventricular Tachycardia

Abstract

The efficacy of diphenylhydantoin in preventing recurrent ventricular tachycardia was studied in ten patients, nine of whom had documented coronary heart disease. Prolonged continuous ECG monitoring of up to 72 hr was performed in each case. Oral and intravenous loading doses of 1000 to 1500 mg were given on the first day of therapy to insure rapid attainment of therapeutic blood levels. Diphenylhydantoin was uniformly ineffective in preventing recurrence of ventricular tachycardia despite the presence of what is regarded as adequate therapeutic plasma concentrations (greater than 19.0 µg/ml in five patients, 10.8-18.0 µg/ml in the remaining five) shortly after onset of ventricular tachycardia. Nystagmus was noted in eight patients, but plasma diphenylhydantoin levels varied widely (8.6-35.0 µg/ml) when this sign of neurotoxicity was first detected.