How does this medication work? What will it do for me?

Flecainide belongs to the class of medications known as antiarrhythmics. It is used to treat or prevent abnormal heart rhythms in certain conditions (e.g., paroxysmal supraventricular tachycardias, sustained ventricular tachycardia). It works by slowing down the rate of nerve impulses causing the heart to beat, and by making the heart less likely to respond to abnormal impulses.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

50 mg
Each white, round, unscored tablet, imprinted with "3M" on one side and "TR 50" on the other side, contains flecainide acetate 50 mg. Nonmedicinal ingredients: croscarmellose sodium, hydrogenated vegetable oil, magnesium stearate, microcrystalline cellulose, and starch. Tartrazine-free.

100 mg
Each white, round, scored tablet, embossed with "3M" on one side and "TR 100" on the other side, contains flecainide acetate 100 mg. Nonmedicinal ingredients: croscarmellose sodium, hydrogenated vegetable oil, magnesium stearate, microcrystalline cellulose, and starch. Tartrazine-free.

How should I use this medication?

The usual recommended adult starting dose of flecainide is 50 mg to 100 mg twice daily, depending on the type of abnormal heart rhythm being treated. Usually, this medication is taken every 8 to 12 hours. The dose and interval may be changed by your doctor according to your response to the medication. Flecainide can be taken with or without food. For some people, this medication is started in the hospital, where heart rhythm can be closely monitored.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Do not take this medication if you:

  • are allergic to flecainide or any ingredients of the medication
  • have certain types of heart problems not managed by a pacemaker (second- or third-degree atrioventricular block, or bifascicular or trifascicular bundle branch block)

This medication should not be given to people who are in cardiogenic shock.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • abdominal pain
  • blurred vision
  • constipation
  • cough
  • dizziness
  • dry mouth
  • fatigue
  • headache
  • muscle or joint pain
  • nausea
  • nervousness
  • rash
  • sweating
  • tingling sensation
  • tremor

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • heart palpitations
  • shortness of breath
  • vision problems (e.g., seeing double, sensitivity to light)
  • worsening symptoms of congestive heart failure, e.g.:
    • cough
    • fast heartbeat
    • fatigue
    • swollen feet or ankles

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • chest pain
  • fainting
  • irregular heartbeat
  • signs of a serious allergic reaction, e.g.
    • difficulty breathing
    • hives
    • swelling of face or throat
  • symptoms of liver problems, i.e.:
    • abdominal pain
    • dark urine
    • light-coloured stools
    • nausea
    • vomiting
    • yellowing of the skin or eyes

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Abnormal heart rhythms: Certain medications used to treat abnormal heart rhythms, including flecainide, may cause new abnormal heart rhythms or worsen existing ones. Your doctor will monitor you closely while you are taking flecainide. If you experience a fast, slow, or irregular heartbeat; fainting; heart palpitations; or dizziness while taking this medication, contact your doctor immediately.

Drowsiness/reduced alertness: Flecainide may cause blurred vision, dizziness, and fatigue. Do not drive or operate machinery until you know how this medication affects you.

Heart failure: Flecainide can cause or worsen heart failure and should not be used by people with severe or untreated heart failure. If you have heart failure and are taking this medication, your doctor will monitor you closely during treatment. If you notice shortness of breath, weight gain, or swelling in the hands, feet, or lower legs while taking flecainide, contact your doctor immediately. People who have had a heart attack may also develop these symptoms.

Kidney or liver problems: If you have decreased kidney or liver function discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: Flecainide passes into breast milk. If you are a breast-feeding mother and are taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

What other drugs could interact with this medication?

There may be an interaction between flecainide and any of the following:

  • antiarrhythmia medications (e.g., amiodorone, disopyramide, procainamide, quinidine, pimozide)
  • beta-blockers (e.g., atenolol, metoprolol, propranolol)
  • calcium channel blockers (e.g. diltiazem, verapamil)
  • carbamazepine
  • cimetidine
  • digoxin
  • dronedarone
  • nilotinib
  • phenobarbital
  • phenytoin
  • ritonavir
  • saquinavir
  • tetrabenazine
  • thioridazine
  • tipranavir
  • ziprasidone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.