Studies on Digitalis. I. Direct Effects on Peripheral Vascular Resistance

There is a substantial body of evidence which supports the view that the action of digitalis preparations is not limited to the heart. It had been suggested that the primary action of digitalis is extracardiac (1-3) and that the direct effects on the vascular bed may be responsible, in part, for its therapeutic action (4). However, in most studies, attention has been directed to the power- ful positive inotropic action of this drug (5-10). The direct effects of digitalis on the peripheral circulation alone have not been clearly defined be- cause of alterations in the cardiac output which usually accompany digitalization. The present study was designed to characterize the direct effects of several digitalis glycosides on vascular resistance in the dog. Two types of preparations were employed in which the circulatory effects resulting from the inotropic action of these drugs could be completely eliminated.