Flecainide Acetate

Medically Reviewed by Dr. Harshi Dhingra, M.D.

Last Reviewed: Apr 11, 2024

Warnings

Flecainide Risks, Warnings, and Complications

Flecainide can cause or worsen serious health problems in some people. Talk with your doctor about other treatment options for irregular heart rhythms if you are at a high risk of complications from this medication. Some of the risks of flecainide use include:

INCREASED RISK OF DEATH AFTER HEART ATTACKS: The Cardiac Arrhythmia Suppression Trial (CAST) showed that the risk of death after a recent heart attack is higher in patients receiving encainide and flecainide compared to people who did not take these medications. If you have had a heart attack in the last two years, your cardiologist will choose an appropriate antiarrhythmic drug carefully.
NEW ABNORMAL HEART RHYTHMS: Unlike other antiarrhythmics, flecainide has proarrhythmic effects, meaning it can cause new abnormal heart rhythms. This medication is not recommended for individuals with chronic atrial fibrillation (long-standing atrial fibrillation). It is only used to treat paroxysmal atrial fibrillation (which occurs on and off). It is also only prescribed for ventricular arrhythmias if they are life-threatening. Your doctor will have you stay in the hospital for careful monitoring of your heart rhythm when first starting flecainide therapy. Tell your doctor immediately if you develop chest pain, palpitations, dizziness, or fainting during treatment with this medicine.
HEART FAILURE: Flecainide can cause or worsen heart failure. This medication may not be right for you if you have congestive heart failure or structural heart disease. Call your doctor right away if you develop a build-up of fluid and swelling in your arms or legs while on flecainide.
ECG CHANGES: Flecainide slows electrical conduction in the heart and can lead to ECG changes such as PR, QRS, and QT prolongation. Your doctor will prescribe the lowest effective dose of flecainide to minimize these effects. They may lower your flecainide dose or discontinue treatment with this drug if you develop ECG changes.
SLOWED HEART RHYTHM: Flecainide should be used with caution in people with sick sinus syndrome because it can cause bradycardia (slow heartbeat), sinus pause, or sinus arrest in such individuals.

Precautions Before Starting Flecainide

Tell your doctor if you have ever had allergic reactions to flecainide, any of the active or inactive ingredients in flecainide tablets, or any other medications. Your pharmacy can give you a list of ingredients.

Give your doctor and pharmacist a complete list of all your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal products. This can help prevent possible interactions between flecainide and your other drugs.

Give your doctor a complete medical history. Flecainide may not be safe for people with certain medical conditions, such as heart block (a condition in which electrical signals are not conducted normally from the atrial muscle fibers (upper chambers) to the ventricles (lower chambers) of the heart), heart disease including heart attack or heart failure, high or low potassium levels, kidney disease, or liver disease. Tell your doctor if you have a pacemaker in place.

Inform your doctor if you are pregnant, could be pregnant, are planning a pregnancy, or are breastfeeding.

Tell your doctor if you eat a strict vegetarian diet.

If you are giving flecainide to an infant, tell the doctor if there are any significant changes in the baby’s milk intake, as this can affect the absorption of the drug.

Precautions During Use of Flecainide

Keep all your medical and lab appointments during treatment with flecainide. Your doctor may want to adjust your dose, order certain laboratory tests, and monitor your heart rhythm.

Do not start, stop, or change any medications while on flecainide without your doctor’s approval.

Tell all your healthcare professionals you are taking flecainide, especially if you are having a surgical procedure, including dental treatment.

Tell your doctor if you become pregnant while on this medicine

Flecainide Drug Interactions

Taking flecainide with certain other drugs can affect how it works. Possible drug interactions between flecainide and your other medications can increase the risk of severe adverse events. Your doctor may change the dose of your medications, switch you to a different medication, and/or monitor you carefully for serious side effects if there are known interactions between flecainide and your other medicines. Some of the medications that can interact with flecainide include:

Carbonic anhydrase inhibitors such as acetazolamide (Diamox), dichlorphenamide, and methazolamide
Other antiarrhythmics like amiodarone (Cordarone, Pacerone), disopyramide (Norpace), and quinidine
Antacids
H2 blockers such as cimetidine (Tagamet)
Ammonium chloride
Beta-blockers such as metoprolol (Lopressor, Toprol XL), labetalol (Trandate), atenolol (Tenormin), propranolol (Inderal), and nadolol (Corgard)
Calcium channel blockers such as diltiazem (Cardizem, Tiazac), verapamil (Calan, Verelan), and nifedipine (Adalat, Procardia)
Heart medications such as digoxin (Lanoxin)
Anti-seizure drugs such as carbamazepine (Carbatrol, Tegretol), phenytoin (Dilantin), and phenobarbital
Antipsychotics such as clozapine (Clozaril)
Sodium bicarbonate (baking soda, Soda Mint, Citrocarbonate)

The above list may not include all the possible interactions of flecainide. Give your doctor or pharmacist a complete list of your medications, including prescription drugs, over-the-counter medicines, dietary supplements, and herbal remedies. Also, tell your healthcare provider if you smoke, drink alcohol, or use recreational drugs because some of these substances can cause serious health complications when used with prescription and over-the-counter medicines.

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