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Flecainide (By mouth)

Flecainide (FLEK-a-nide)

Used to prevent or treat irregular heartbeats (arrhythmias) that are serious. Belongs to a class of drugs called antiarrhythmics.

Brand Name(s):


There may be other brand names for this medicine.

When This Medicine Should Not Be Used:

You should not use this medicine if you have had an allergic reaction to flecainide or if you have certain heart problems. Your doctor will determine if this medicine is right for you.

How to Use This Medicine:


  • You will receive your first dose of this medicine in a hospital. Your doctor will watch you closely after you take this medicine to make sure you do not have any serious side effects.
  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.
  • This medicine may be taken with or without food.
  • You may need to carry identification stating that you are taking flecainide. Ask your doctor about this.
  • In infants (less than 2 years of age) who drink a lot of milk, your doctor may adjust the dose of this medicine when it is time to reduce the amount of milk your infant is receiving, or if they develop gastroenteritis. Talk with your doctor if you have questions about this.

If a dose is missed:

  • If you take your medicine two times a day and you miss a dose, take it as soon as possible unless you are more than 6 hours late.
  • If you are more than 6 hours late, skip the missed dose, and take your medicine at your usual time.
  • You should not use two doses at the same time.

How to Store and Dispose of This Medicine:

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Drugs and Foods to Avoid:

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • Make sure your doctor knows if you are using other medicine for heart rhythm problems (such as amiodarone, disopyramide, quinidine, Cardioquin®, Cordarone®, Norpace®, or Quinaglute®), certain blood pressure medicine (such as atenolol, diltiazem, metoprolol, nifedipine, propranolol, timolol, verapamil, Adalat®, Calan®, Cardizem®, Inderal®, Isoptin®, Procardia®, Toprol®, or Verelan®), carbamazepine (Tegretol®), cimetidine (Tagamet®), digoxin (Lanoxin®), phenobarbital (Luminal®), phenytoin (Dilantin®), or a diuretic or "water pill" (such as hydrochlorothiazide [HCTZ], furosemide, torsemide, Demadex®, or Lasix®).

Warnings While Using This Medicine:

  • Make sure your doctor knows if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, heart disease, heart rhythm problems (such as prolonged PR, QRS, or QT intervals or sick sinus syndrome), a recent heart attack, congestive heart failure, or if you have a pacemaker.
  • Check with your doctor right away if you develop any of the following: chest pain; shortness of breath; swelling of your hands, ankles, or feet; or weight gain. These may be symptoms of heart failure.
  • This medicine can cause changes in your heart rhythm, such as conditions called PR, QRS, or QT prolongation. It may cause fainting or serious side effects in some patients. Contact your doctor right away if your symptoms do not improve or if they get worse.
  • Tell any doctor or dentist who treats you that you are using this medicine. You may need to stop using this medicine several days before you have surgery or medical tests.
  • Do not stop using this medicine suddenly. Your doctor will need to slowly decrease your dose before you stop it completely.
  • This medicine may make you dizzy or drowsy. Avoid driving, using machines, or doing anything else that could be dangerous if you are not alert.
  • Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments.

Possible Side Effects While Using This Medicine:

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Chest pain.
  • Fast, pounding, or uneven heartbeat.
  • Fever or chills.
  • Lightheadedness, dizziness, or fainting.
  • Shortness of breath or troubled breathing.
  • Swelling in your hands, ankles, or feet.
  • Tremors.
  • Yellowing of your skin or the whites of your eyes.

If you notice these less serious side effects, talk with your doctor:

  • Headache.
  • Diarrhea, constipation, nausea, vomiting, loss of appetite, or stomach pain or cramps.
  • Tiredness or weakness.
  • Vision changes such as trouble focusing or seeing spots.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Last Updated: 5/1/2020

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