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Overview: Flecainide is taken for certain types of abnormal heart rhythms. It helps your heart beat normally. Common side effects include dizziness, headache, and nausea. Notify your healthcare provider right away if you notice new swelling in your hands, feet, or legs.

Uses

What is flecainide used for?

Flecainide is commonly used to help prevent certain types of fast, irregular heartbeats, like paroxysmal supraventricular tachycardia (PSVT) and paroxysmal atrial fibrillation/flutter (PAF), when these cause serious symptoms.

Flecainide is also used to help prevent an abnormal heartbeat or rhythm in the lower parts of the heart, called the ventricles. This is called ventricular arrhythmia. Flecainide is only for people with serious ventricular arrhythmias, such as sustained ventricular tachycardia. 

Flecainide may also be used for other conditions as determined by your healthcare provider.

How does flecainide work (mechanism of action)?

Flecainide works by blocking certain electrical signals in the heart that cause it to beat too fast or irregularly. This helps the heart beat normally again.

How is flecainide supplied (dosage forms)?

Dosage forms and strengths

  • 50 mg, 100 mg, 150 mg oral tablets

How should I store flecainide?

Flecainide should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. Protect from light.

Side Effects

What are the most common side effects of flecainide?

The most common side effects of flecainide are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Dizziness
  • Vision changes, such as blurry vision or trouble focusing
  • Shortness of breath
  • Headache
  • Nausea
  • Tiredness
  • Feeling of skipped heartbeats
  • Chest pain

There may be other side effects of flecainide that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of flecainide?

While less common, the most serious side effects of flecainide are described below, along with what to do if they happen.

Heart Rhythm Changes. Flecainide may cause serious heart rhythm problems that can lead to an irregular heartbeat and fainting. In rare cases, this may cause the heart to suddenly stop beating (cardiac arrest). Some people have a higher risk of this, including people with existing heart disease or who take other medicines that affect the heart. Get emergency help if you have any of the following signs of heart rhythm changes.

  • Chest pain
  • Shortness of breath
  • Feeling dizzy, lightheaded, or fainting
  • Changes in your heart rate or rhythm, such as a fast, slow, pounding or skipping heartbeat

Heart Failure. Flecainide can cause new or worsening heart failure. The risk is higher in people who already have heart failure or a history of heart problems. Tell your healthcare provider right away if you have any of the following symptoms of heart failure.

  • Shortness of breath or trouble breathing, especially while lying down
  • Swelling in your feet, ankles, or legs
  • Unusually fast weight gain
  • Unusual tiredness

Severe Allergic Reactions. Flecainide may cause allergic reactions, which can be serious. Stop taking flecainide and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use flecainide?

Allergies to Ingredients. People who are allergic to any of the following should not take flecainide.

  • Flecainide
  • Tambocor
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific flecainide products they stock.

Heart Block. People who have certain types of heart block, including atrioventricular (AV) block, should not use flecainide unless they have a pacemaker and are continuously monitored. 

What should I know about flecainide before using it?

Do not take flecainide unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share flecainide with other people, even if they have the same condition as you. It may harm them.

You will likely start taking flecainide at a hospital or clinic so your healthcare provider can closely monitor your heart rate and rhythm.

Your healthcare provider may check your blood levels of flecainide periodically to help make sure it is in a safe and effective range. Keep all appointments to have your blood work checked.

Flecainide can affect your alertness or coordination. Do not drive or do other activities that require alertness or coordination until you know how flecainide affects you.

Keep flecainide out of the reach of children.

What should I tell my healthcare provider before using flecainide?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if flecainide is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

Other Medicines and Supplements. Flecainide may interact with other medicines and supplements. Before using flecainide, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section below for more details.

Pregnancy. It is not known if or how flecainide could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. Flecainide passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take flecainide while breastfeeding.

Interactions

Does flecainide interact with foods or drinks?

Milk may decrease how much flecainide is absorbed in babies. Tell your healthcare provider if your baby starts or stops drinking milk. 

It is unknown if drinking alcohol will affect flecainide. The risk of dizziness may be increased if you drink alcohol while taking flecainide.

Does flecainide interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using flecainide.

  • Phenytoin (Dilantin, Phenytek, and others), which is a medicine to control seizures
  • Propranolol (Inderal LA, Innopran XL), which is a medicine that may be used for certain heart conditions or to reduce blood pressure
  • Any medicine used to control your heart rate or rhythm (antiarrhythmic)
  • Verapamil (Verelan, Verelan PM), which is a medicine used for high blood pressure or chest pain
  • Diltiazem (Cardizem CD and others), which is a medicine used for high blood pressure and other conditions
  • Nifedipine (Adalat, Procardia XL), which is a medicine used for high blood pressure or chest pain
  • Cimetidine (Tagamet HB), which is a medicine used for heartburn
  • Carbamazepine (Tegretol, Carbatrol, and others), which is a medicine commonly used to treat seizures or nerve pain
  • Phenobarbital, which is a medicine that may be used to treat seizures

Some other medicines may alter the blood levels of flecainide. Tell your healthcare provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with flecainide. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much flecainide?

If you or someone else has used too much flecainide, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of flecainide?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.