Some effects of diphenylhydantoin and propranolol on the cardiovascular system

The effect of diphenylhydantoin sodium (Dilantin) on the peripheral circulation and on the work capacity of the left ventricle was studied and compared with that of another antiarrhythmic drug, the beta-adrenergic antagonist, propranolol. Dilantin (3.5 mg. per kilogram) caused a decline in the resistance to blood flow in the peripheral circulation and in particular in the coronary, IVC, and SVC circulations. This action of Dilantin was not mediated through the beta-adrenergic receptors. Dilantin (3.5 mg. per kilogram) failed to modify left ventricular work function curves; higher concentrations of diphenyl-hydantoin did, however, depress the capacity of the left ventricle for performing external work. This Dilantin-induced decline in left ventricular work capacity contrasts with that caused by propranolol in that it was associated with an augmented coronary blood flow over a wide range of left ventricular work.