Antiarrhythmic Medications: Flecainide

Flecainide is an antiarrhythmic medication. It treats paroxysmal supraventricular tachycardia (PSVT), a potentially life-threatening irregular heartbeat. The prescription drug can slow or block electrical signals in the heart and stabilize the heartbeat. People taking flecainide should be monitored closely for problems with the heart, liver and kidneys.

What is flecainide?

Flecainide is a prescription antiarrhythmic medication. It treats a life-threatening irregular or abnormal heartbeat. The brand name is Tambocor®.


Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy

What is flecainide used for?

Flecainide is used to treat a specific life-threatening type of arrhythmia called paroxysmal supraventricular tachycardia (PSVT).

Normally, the four chambers of the heart contract (beat) in a predictable, coordinated way. PSVTs are sudden, occasional, rapid heartbeats that start somewhere above the lower heart chambers (ventricles).

Examples include:

  • Atrial fibrillation, a fast, chaotic rhythm in the atria (upper chambers of the heart).
  • Atrial flutter, when the atria beat too quickly.
  • Atrioventricular nodal reentrant tachycardia (AVNRT).

Flecainide may also be used to treat life-threatening sustained ventricular tachycardia.

How does flecainide work?

Flecainide can slow or block electrical signals in the heart and stabilize the heartbeat.


How should I take flecainide?

Flecainide comes in tablets that you swallow. Your healthcare provider will give you specific instructions on how to take flecainide.

Most people on flecainide take two tablets each day, one every 12 hours. Take it with or without food at about the same times every day.

The starting dose is typically 50 or 100 milligrams (mg), depending on the arrhythmia being treated. Your healthcare provider may increase the amount every few days, working up to the optimal dose for you.

Your dose may depend on:

  • Age.
  • Other medical conditions and overall health.
  • Other medications you’re taking.
  • Response to the treatment.
  • Whether you’re breastfeeding (chestfeeding).

Your healthcare provider will monitor you carefully when you start flecainide and for as long as you take it. You may even stay in the hospital when you start taking flecainide in case you have any adverse reactions.

What are the benefits?

Flecainide is used only in people with serious, life-threatening arrhythmia. The medication can slow or block irregular heartbeat, preventing stroke and sudden cardiac death.


What are the risks of using flecainide?

Flecainide is associated with some health risks, including possible:

  • Allergic reaction.
  • Heart attack in people who have already had a heart attack.
  • New or worse arrhythmia.
  • Heart failure (often called congestive heart failure).
  • Liver problems.
  • Kidney problems.

People taking flecainide should be monitored closely for problems with the liver and kidneys.

The drug should be used while pregnant only when necessary. People who are breastfeeding and taking flecainide should be monitored to measure the amount of the drug released into breast milk.

Can you overdose on flecainide?

Flecainide overdose can be fatal. If you miss a dose, take it as soon as you remember, within six hours. But don’t take it too close to your next dose, and don’t double your next dose.

What are the possible side effects of using flecainide?

Flecainide can cause side effects. Tell your healthcare provider if any of them are severe or don’t go away. Common side effects may include:

If you have any of these serious side effects, report them to your healthcare provider right away:

  • Chest pain.
  • Confusion.
  • Cough that won’t go away, or a cough that produces mucus containing blood.
  • Extreme fatigue (tiredness).
  • Fainting.
  • Fast or pounding heartbeat.
  • Flu-like symptoms, including fever.
  • Nausea or loss of appetite.
  • Shortness of breath.
  • Swelling in the hands, feet or lower legs.
  • Sudden weight gain.
  • Unusual bleeding or bruising.
  • Yellowish skin or eyes.

Allergic reactions to flecainide are rare. But report any signs of allergy to your healthcare provider, such as:

  • Itchy skin.
  • Swelling of the face, lips, tongue or throat.
  • Wheezing when you breathe.

What other drugs can flecainide interact with?

Tell your healthcare provider if you’re taking any other medications or supplements. Some can interfere or interact with flecainide, including:

  • Acetazolamide, which treats altitude sickness, glaucoma and other conditions.
  • Antacids for heartburn, indigestion or an upset stomach.
  • Antiseizure medications, including phenytoin and phenobarbital.
  • Beta-blockers, which reduce blood pressure.
  • HIVtreatments, such as ritonavir and tipranavir.
  • Medications for Tourette syndrome, such as pimozide.
  • Other antiarrhythmic medications, including amiodarone, dofetilide, procainamide, quinidine and sotalol.
  • Some antibiotics, such as erythromycin.
  • Some antifungals, such as fluconazole.
  • Ulcer treatments, such as cimetidine.

How long should you take flecainide?

Flecainide can control arrhythmia, but it cannot cure it. You may take flecainide for a long period of time, even for the rest of your life.

Don’t stop taking flecainide without talking to your healthcare provider. Not taking the medication can make a heart condition worse.

Who should not take flecainide?

You should not take flecainide if you have certain other medical conditions, particularly other heart conditions. Your healthcare provider may advise against flecainide if you have conditions such as:

  • Bundle branch block, a delay or blockage in electrical impulses as they travel through your heart to make it beat.
  • Other kinds of arrhythmia that cause a slow heartbeat. Examples include heart block (also called atrioventricular or AV block) or sick sinus syndrome (also called sinus node dysfunction or sinus node disease).
  • QT prolongation, when the heart muscle takes longer than normal to recharge between beats.
  • Structural problems in the heart.

Tell your healthcare provider about any other health conditions you have to ensure that flecainide is safe for you.

A note from Cleveland Clinic

Flecainide is a prescription antiarrhythmic medication. It can’t cure arrhythmia, but it can help prevent irregular or abnormal heartbeat, stroke and sudden cardiac death. Your healthcare provider will monitor you carefully to make sure the drug doesn’t cause other heart problems or issues with the kidneys or liver.

Medically Reviewed

Last reviewed on 06/23/2022.

Learn more about our editorial process.

Appointments 800.659.7822