Antiarrhythmic pharmacology is often categorized according to the Vaughan Williams classification system. This system classifies 4 groups of medications according to their mechanism of action, with 3 of the 4 groups impacting the cardiac action potential. The fourth group in this classification system exerts its antiarrhythmie effect by blocking the beta1-adrenergic receptors of the sympathetic nervous system. One limitation of this classification system is that most medications impacting the cardiac action potential affect more than 1 ion channel. Although calcium channel Mockers impact the slow calcium channel of the cardiac action potential, they are considered safer medications than those that block the fast sodium channel and the potassium channel. This column focuses on the cardiovascular and electrophysiological effects of sodium and potassium channel blockers and other important clinical considerations in the care of patients receiving these class I and class III agents. If a medication is temporarily placed on hold for a clinical reason, the clinician must plan for return of the arrhythmia for which the patient is being treated. Because of the high-risk features of sodium and potassium channel blockers, nursing knowledge is vital to ensure optimal assessment, counseling, and evaluation of medication effect.
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