Antiarrhythmic agents

This broad family of medication ceases arrhythmia, maintains the heartrate and/or slows the heartbeat. It is divided into four groups: class I (act on the canals that carry sodium), class II (beta-blockers), class III (act on the canals that carry potassium) and class IV (calcium channel blockers). Below, we will explain some of the most frequently used molecules in class I and class III. For class II and IV molecules, refer to the descriptions above.


A)    Class I: flecainide [Tambocor™], propafenone [Rythmol™]

These two molecules prevent the sodium ion to enter the cardiac cells. This causes the arrhythmia to stop and/or to maintain the heart at a regular rate.

There are two ways to use these molecules.

Medication taken “when needed”, also called “pill in the pocket”, applies to people who periodically have arrhythmia and who feel it. When someone feels an irregular heartbeat, he or she takes a dose in order to stop the arrhythmia.

Daily and regular usages of these medications are also possible. In general, these two molecules are taken two or three times per day.

The most frequent undesirable side effects are dizziness and nausea. The propafenone can also provoke bad taste in the mouth.


B)    Class III : sotalol [Sotacor™], amiodarone [Cordarone™]

These two molecules work to prevent the potassium ion from exiting the cardiac cells. This stops arrhythmia and/or maintains a regular heartbeat.

While amiodarone and sotalol are part of the same class, they both have other properties that distinguish them from each other.


In addition to its ability to block potassium transporters, sotalol also acts as beta-blockers (see #3 above for more details on beta-blockers). It is not used, however, as a solution to arrhythmia.

Sotalol is usually taken twice per day.

The most frequent side effects are dizziness and fatigue.



Amiodarone is a molecule with various usages. It is capable of being efficient at four different levels as anti-arrhythmic. It has the properties of the anti-arrhythmic molecules of classes I, II, III and IV. This allows Amiodarone to be effective for many types of rhythmic heart problems.

Amiodarone is usually taken between once and three times daily. During the first few days or weeks of the treatment, stronger doses are necessary in order to obtain a faster efficiency. Then, the dose is reduced.

The most frequent undesirable effects are nausea and vomiting. These side effects are usually present with the stronger doses used at the beginning of the treatment. The skin also becomes more sensible in the sun.

When amiodarone is used over a long period, certain follow-ups are necessary: amiodarone may cause irregularities in your vision, liver enzymes and thyroid gland enzymes.


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