Electrolyte and antiarrhythmic drug interaction

Abstract When one considers the complex interaction of antiarrhythmic drugs, either among the various groups or in the presence of altered electrolytes, the number of possible antagonistic and synergistic actions becomes almost infinite. This overview has attempted to amalgamate present information concerning drug and electrolyte interactions. Fortunately, in the clinical setting one is usually operating within the physiologic range for serum electrolytes, and many of these alterations shown in laboratory studies may not be pertinent. It should be remembered, however, that when serum electrolyte derangements are present, the usual or expected effects of antiarrhythmic drugs may be masked, leading to erroneous therapy or to the conclusion that the therapy is either inadequate or useless. This summary also points out that marked beneficial effects can be achieved, particularly by the use of digitalis and propranolol, in slowing AV conduction in the presence of supraventricular arrhythmias and that low potassium completely nullifies the action of the quinidine-like or Group 1 agents. The antagonism of bretylium to quinidine-like agents should alert the clinician to the possibility that the administration of Group 1 drugs in the wake of Group 3 or possibly other antiarrhythmic drugs may either nullify or aggravate certain pharmacologic actions. Although it is true that quinidine, lidocaine, and procainamide can be used with increased efficacy in the presence of propranolol, the opposite may be true when they are used in the presence of bretylium. Precise monitoring of serum electrolytes would appear essential before and during antiarrhythmic drug therapy.