Abstract
Diphenylhydantoin (Dilantin), 5 mg/kg., given intravenously over five minutes during the infusion of ouabain, 45 μg/kg. per hr., transiently but significantly reduced the augmentation in right ventricular contractile force which had been produced by the glycoside in 10 anesthetized open chest dogs (group I). The magnitude of the reduction in contractile force and the duration of this effect were similar to those which occurred in 10 animals given Dilantin alone (group III). The administration of Dilantin during the infusion of isoproterenol (group IV, 6 animals) or after propranolol (group V, 5 animals) produced a decrease in contractile force, the magnitude of which was similar to that observed in the dogs given Dilantin alone. The duration of this effect of Dilantin in the dogs receiving isoproterenol also was similar to that observed in the groups I and III. Dilantin resulted in the deaths of 2 animals pretreated with propranolol and caused prolonged periods of contractile force alternans in another 2 animals in this group. The administration of Dilantin during the infusion of ouabain did not significantly increase the amount of glycoside required to produce arrhythmias or affect the maximal increase in contractile force produced by ouabain before the appearance of an arrhythmia. It is concluded that Dilantin does transiently reduce the positive inotropic action of ouabain. However, this effect of Dilantin is not directed specifically against the inotropic effect of the glycosides and apparently occurs as a result of the direct myocardial depressant properties of Dilantin.
Published Version
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