Combination therapy for cardiac arrhythmias.

Combinations of antiarrhythmic agents are often used when single agents are ineffective, only partly effective or poorly tolerated. The theoretical and experimental basis for combination therapy for arrhythmias is the dissimilar electrophysiologic properties of antiarrhythmic agents. Until more is known about the mechanism of drug synergism and drug interactions, the experience gained clinically remains essential to our understanding. Published reports contain numerous data on the effectiveness of various combinations of antiarrhythmic agents, including combinations of class I agents, the combination of a class I agent and a beta-blocking agent or amiodarone, and combinations including a calcium-antagonist agent. Adverse drug interactions, however, can occur, and combinations of certain agents must be avoided or used with caution.