Antiarrhythmics are medications used to prevent or terminate arrhythmias, abnormal heart rhythms resulting from a disturbance in the heart’s electrical system. These medications are used in a number of situations. They may be used to terminate an acute arrhythmia in an emergency situation, to prevent the recurrence of an arrhythmia, or to lower the risk of an arrhythmia that has not yet occurred in a high-risk patient.

These medications work in a number of ways, depending on the type of arrhythmia and kind of medication. In general, the leading class of antiarrhythmics (class I) interferes with the flow of ionized minerals through the heart. These minerals include sodium and calcium, which can cause the heart to beat too rapidly (tachyarrhythmias).  Physicians may need to experiment with a number of antiarrhythmics to find one that effectively treats a patient's particular condition.

A physician will use a particular drug (or class of drugs) based on the patient’s medical history, specific type of arrhythmia, type of underlying heart disease (if present) and current symptoms. Though antiarrhythmic medications often manage the problem quite effectively, they cannot cure it. In many cases, antiarrhythmic medications need to be taken for life.

Some forms of arrhythmia are resistant to drug therapy alone, and are best treated surgically with implanted devices such as a pacemaker or an implantable cardioverter defibrillator (ICD). Other forms of arrhythmias may be treated with radiofrequency ablation. Anti-arrhythmic medications are sometimes used in conjunction with ICDs to reduce the risk of life-threatening tachyarrhythmias.