Antiarrhythmics are used to treat heart rhythm disorders, called arrhythmias, and to lessen the symptoms associated with them.

Why do I need to take an antiarrhythmic?

Antiarrhythmics are used to treat heart rhythm disorders, called arrhythmias, and to lessen the symptoms associated with them. Some of the common symptoms of arrhythmias include heart palpitations, irregular heartbeats, fast heartbeats, lightheadedness, fainting, chest pain, and shortness of breath.

How do antiarrhythmics work?

Irregular heartbeats may be a congenital condition (you are born with it) or may develop if part of the heart muscle tissue (myocardium) is irritated or damaged, leading to a disruption or “short circuit” in the heart’s electrical system. Antiarrhythmics work in a variety of ways to slow the electrical impulses in the heart so that the heart can resume a regular rhythm.

Antiarrhythmic medicines are split into four categories:

  • Class I antiarrhythmic medicines are sodium-channel blockers, which slow electrical conduction in the heart.
  • Class II antiarrhythmic medicines are beta-blockers, which work by blocking the impulses that may cause an irregular heart rhythm and by interfering with hormonal influences (such as adrenaline) on the heart’s cells. By doing this, they also reduce blood pressure and heart rate.
  • Class III antiarrhythmic medicines slow the electrical impulses in the heart by blocking the heart’s potassium channels.
  • Class IV antiarrhythmic medicines work like class III medicines but act by blocking the calcium channels in the heart.

Digoxin is another example of a medicine that can be used as an antiarrhythmic, although it is not included in the above categories.

Because each class of medicine works in a slightly different way, there is no one medicine to treat every kind of arrhythmia. Sometimes an antiarrhythmic medicine can cause more arrhythmias or make your arrhythmia worse (called proarrhythmia). Finding which medicine works best for you may mean working closely with your doctor and trying a few different kinds of medicines. Some patients may need extra monitoring or testing, either with a Holter monitor or electrophysiology studies (EPS), which can also help doctors clarify what type of antiarrhythmic is best for the patient.

How much do I take?

There are many different kinds of antiarrhythmic medicines and the type and amount varies widely with each individual. You will work closely with your doctor about how and when to take your particular medicine.

What if I am taking other medicines?

Antiarrhythmics can increase or decrease the effects of other medicines that you are taking. These effects are called an interaction. Be sure to tell your doctor and pharmacist about every medicine that you are taking (even over-the-counter medicines and vitamin or herbal supplements), so he or she can make you aware of any interactions.

Because there are so many kinds of medicines, not every interaction is listed here. Interactions are unique to each kind of medicine, but here are some examples of categories of medicines that interact with antiarrhythmics.

  • May reduce the amount of Coumadin (warfarin) that you need to take.
  • May reduce the amount of digoxin you need to take.
  • May affect how your body reacts to insulin or oral diabetes medicines.

While taking certain kinds of antiarrhythmics, your skin may sunburn more easily. Your skin may continue to be sensitive to sunlight for several months even after stopping treatment. You may even get sunburned through a window or cotton clothing. If you are going to be out in the sunlight, wear sunscreen. If you do get a severe sunburn, check with your doctor.

NOTE: If you are taking certain antiarrhythmics, they sometimes cause a blue-gray color to appear on your skin, especially in areas exposed to the sun. After you stop taking that specific medicine, the coloring will go away, but it may take a few months.

What else should I tell my doctor?

Talk to your doctor about your medical history before you start taking an antiarrhythmic. The risks of taking the medicine need to be weighed against its benefits. Here are some things to consider if you and your doctor are deciding whether you should take an antiarrhythmic.

  • You have allergies to foods or dyes. Antiarrhythmics may make your allergic reactions worse.
  • You are thinking of becoming pregnant, you are pregnant, or you are breast-feeding.
  • You are older than 60. Older people may be prone to thyroid problems while taking antiarrhythmics. Older patients also may notice numbness, tingling, or weakness in the hands and feet.
  • You have atrial fibrillation.
  • You have asthma or other lung or breathing problems, such as chronic bronchitis, emphysema, or COPD. Beta-blockers may make your condition worse.
  • You have thyroid problems.
  • You have liver disease.
  • You have kidney disease.
  • You have lupus.
  • You are going to have an operation or dental surgery.

What are the side effects?

Sometimes a medicine causes unwanted effects. These are called side effects. Each antiarrhythmic medicine has its own side effects. Be sure to carefully read the information that your doctor or pharmacist gives you about your medicine. Ask your pharmacist if you do not get any information about side effects with your prescription.

Tell your doctor right away if you think you are having a side effect to this medicine. Do not stop taking your medicine unless your doctor tells you to. If you stop taking your medicine without checking with your doctor, it can make your condition worse.

A consumer-based site by the American Society of Health-System Pharmacists that provides information about all types of medicines as well as safety tips for their proper use. The site’s search feature lets users search medicines by the brand or generic name.


The information in this Medicines for Cardiovascular Disease section has been taken from a number of sources. It is meant to give you information about certain medicines, but it does not cover all of the possible uses, warnings, side effects, or interactions with other medicines and vitamin or herbal supplements. This information should not be used as medical advice for individual problems. Please talk to your doctor and/or your pharmacist for prescription instructions.