Pharmacology of Cardiac Glycosides

Abstract

The term cardiac glycosides is commonly used to represent a wide variety of steroid derivatives that have the property of increasing the force of myocardial contraction and eliciting characteristic electrophysiological effects upon the heart. These substances are contained in many plant and animal sources. The medicinal actions of the squill, or sea onion, were recognized as early as 1500 B.C. The glycosides most frequently used today are derived from the leaves of the foxglove, Digitalis purpurea and D. lanata. The classic study on the actions of digitalis was published in 1785 by William Withering, who described his long experience with digitalis in An Account of the Foxglove, and Some of Its Medicinal Uses: With Practical Remarks on Dropsy and other Diseases {1}. Withering recognized its efficacy in reducing edema and also its notorious tendency to produce toxicity. A second comprehensive monograph was published 14 years later by John Ferrier, who suggested that digitalis might have a cardiac effect. Traube in 1850 also recognized the effect of digitalis in promoting the efficiency of cardiac muscle and further suggested that the bradycardia was the result of vagal stimulation. The usefulness of digitalis preparations in atrial fibrillation was first established in the early twentieth century. Following the purification of the digitalis glycosides, the glycosides became the mainstay of therapy for congestive heart failure.