COMBINED ACTIONS OF QUINIDINE AND DIGITALIS ON THE HEART: AN EXPERIMENTAL STUDY

INTRODUCTION Pharmacologic studies of the combined actions of digitalis and quinidine derive interest largely from the fact that while the two drugs possess some actions in common, they produce, with reference to certain other phenomena, diametrically opposite effects. Such studies have a direct practical bearing as well, because the two drugs are used together widely, especially in the treatment of patients with auricular fibrillation. Many of the clinical observations on quinidine have been made in digitalized patients. In these the fact that the heart may have been fully under the influence of digitalis frequently receives only casual mention or is even overlooked, and the appearance of toxic effects is ascribed to the action of quinidine alone, although some of these effects are never seen in normal animals after comparable doses of quinidine. Experimental studies of the combined action of the two drugs in animals have not been very comprehensive, and