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What are the Different Types of Antiarrhythmic Drugs?

Maggie J. Hall
Maggie J. Hall

According to a standard developed in 1970, there are usually four classifications of anti-arrhythmic medications, including sodium channel blockers, anti-sympathetic nervous system medications, potassium channel blockers, and calcium channel blockers. The first class is generally further subdivided into categories a, b and c, representing weak, moderate, and strong blocking ability. Another group is sometimes called class V, or miscellaneous. Some anti-arrhythmic medications may fall into more than one category, as they produce more than one action.

Class I anti-arrhythmic drugs, or sodium channel blockers, correct arrhythmias by binding to and blocking channels that allow sodium ion access. Either this action produces a longer resting phase before cells become susceptible to contraction stimulation or the action extends the period of time in which the cells receive stimulation before producing a contraction. Physicians generally refer to these phases as the effective refractory period (ERP) and the action potential duration (APD). Medications in this classification might prolong either or both phases, but they generally have no effect on the electrical conduction tissue of the heart. Procainamide, lidocaine and propafenone are examples of class I sodium channel blockers that might be used to treat ventricular tachycardia or atrial fibrillation.

Some individuals need medication to maintain a healthy heart rate.
Some individuals need medication to maintain a healthy heart rate.

Beta blockers, which belong to class II of the antiarrhythmic drugs, typically bind to the beta-adenoceptors of electrical conduction tissue and other cardiac tissue, preventing attachment of the neurotransmitters epinephrine and norepinephrine. Certain medications block β1 and β2 receptor sites, while others only block β1 sites. Blocking neurotransmitter access generally reduces or eliminates stimulation by the sympathetic nervous system. This action usually slows the heart rate by controlling the level of contractility and electrical conduction. Atenolol, carvedilol and propanolol are beta blockers that physicians might use to treat heart attacks, hypertension and tachycardia.

Physicians sometimes prescribe beta blockers to treat patients with high blood pressure.
Physicians sometimes prescribe beta blockers to treat patients with high blood pressure.

Potassium channel blockers, comprising the class III anti-arrhythmic drugs, bind to channels of nonconductive tissue that allow potassium ions to leave the cell. This action not only prolongs the relaxation phase (ERP), but also extends the amount of time cells require to become adequately stimulated and produce a contraction (APD). These actions control tachycardia by preventing premature stimulation produced by anomalous triggers. Some medications in this group perform actions of more than one class. Amiodarone, though considered a potassium channel blocker, also displays properties of the class I, II, and IV medications, and sotalol is also a beta blocker.

Calcium channel blockers are sometimes prescribed for patients who suffer from hypertension.
Calcium channel blockers are sometimes prescribed for patients who suffer from hypertension.

The class IV anti-arrhythmic agents, known as calcium channel blockers, affect the conductive and nonconductive tissues of the heart along with vascular smooth muscle. Blocking these channels usually prevents calcium ions from entering the cell, which produces relaxation. This action typically slows the heart rate by decreasing conduction speed and the level of contractility. Diltiazem, nifedipine and verapamil are calcium channel blockers that physicians might prescribe for the treatment of angina, atrial fibrillation, tachycardia, or hypertension.

Some antiarrhythmic drugs may be used to treat heart attacks or other heart conditions.
Some antiarrhythmic drugs may be used to treat heart attacks or other heart conditions.

Adenosine and digoxin belong to the miscellaneous, or class V group, of anti-arrhythmic drugs that physicians often refer to as cardiac glycosides. These medications affect the heart like other anti-arrhythmics but do so without blocking ions. They generally slow or decrease the conductivity of the heart, though digoxin also extends the refractory period. Cardiac glycosides may be prescribed for tachycardia or atrial fibrillation.

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    • Some individuals need medication to maintain a healthy heart rate.
      By: beerkoff
      Some individuals need medication to maintain a healthy heart rate.
    • Physicians sometimes prescribe beta blockers to treat patients with high blood pressure.
      By: dambuster
      Physicians sometimes prescribe beta blockers to treat patients with high blood pressure.
    • Calcium channel blockers are sometimes prescribed for patients who suffer from hypertension.
      By: Monkey Business
      Calcium channel blockers are sometimes prescribed for patients who suffer from hypertension.
    • Some antiarrhythmic drugs may be used to treat heart attacks or other heart conditions.
      By: WavebreakmediaMicro
      Some antiarrhythmic drugs may be used to treat heart attacks or other heart conditions.
    • Physicians typically refer to digoxin and other miscellaneous anti-arrhythmic drugs as cardiac glycosides.
      By: s_l
      Physicians typically refer to digoxin and other miscellaneous anti-arrhythmic drugs as cardiac glycosides.
    • Various cultures have used rue in folk medicine cures for centuries, due to its potential as a potassium channel blocker.
      By: serenacar
      Various cultures have used rue in folk medicine cures for centuries, due to its potential as a potassium channel blocker.
    • Antiarrhythmic drugs slow or decrease the conductivity of the heart.
      By: lestyan
      Antiarrhythmic drugs slow or decrease the conductivity of the heart.
    • Doctors may prescribe a antiarrhythmic drug for certain conditions.
      By: emiliau
      Doctors may prescribe a antiarrhythmic drug for certain conditions.