This medication is used to help prevent certain types of serious (possibly fatal) irregular heartbeat (such as paroxysmal supraventricular tachycardia and atrial fibrillation). It is used to help maintain a regular, steady heartbeat. Propafenone is known as an anti-arrhythmic drug. It works by blocking the activity of certain electrical signals in the heart that can cause an irregular heartbeat. Treating an irregular heartbeat can decrease the risk for blood clots, and this effect can reduce your risk of heart attack or stroke.

Read the Patient Information Leaflet if available from your pharmacist before you start taking propafenone extended-release capsules and each time you get a refill. If you have any questions, ask your doctor or pharmacist.

Take this medication by mouth with or without food as directed by your doctor, usually every 12 hours. Swallow the capsules whole. Do not crush or chew the capsules. Doing so can release all of the drug at once, increasing the risk of side effects.

The dosage is based on your medical condition and response to treatment.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same times each day.

Avoid eating grapefruit or drinking grapefruit juice while using this medication unless your doctor or pharmacist says you may do so safely. Grapefruit can increase the chance of side effects with this medicine. Ask your doctor or pharmacist for more details.

Tell your doctor if your condition does not get better or if it gets worse.

See also Warning section.

Dizziness, headache, metallic/salty taste in the mouth, nausea/vomiting, constipation, anxiety, and tiredness may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• signs of infection (such as sore throat that doesn't go away, high fever, severe chills, weakness)
• signs of liver problems (such as nausea/vomiting that doesn't stop, stomach/abdominal pain, yellowing eyes/skin, dark urine)
• worsening symptoms of heart failure (such as shortness of breath, swelling ankles/feet, unusual tiredness, unusual/sudden weight gain)

Get medical help right away if you have any very serious side effects, including:

• fainting
• faster/more irregular heartbeat
• severe dizziness

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking propafenone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• breathing problems (such as asthma, chronic bronchitis, emphysema)
• kidney problems
• liver problems
• myasthenia gravis
• a certain inherited heart condition (Brugada Syndrome)

Propafenone may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away.

The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may cause QT prolongation. Before using propafenone, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions:

• certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG)
• family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death)

Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using propafenone safely.

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially QT prolongation (see above).

This medication can affect fertility in males. Ask your doctor for more details.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Many drugs besides propafenone may affect the heart rhythm (QT prolongation), including amiodarone, dofetilide, flecainide, pimozide, procainamide, quinidine, sotalol, macrolide antibiotics (such as erythromycin), and certain quinolone antibiotics (such as sparfloxacin), among others.

Other medications can affect the removal of propafenone from your body, which may affect how propafenone works. Examples include asunaprevir, desipramine, ketoconazole, orlistat, phenobarbital, phenytoin, ritonavir, certain HIV protease inhibitors (such as tipranavir), among others.

Propafenone can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include digoxin, fezolinetant, imipramine, metoprolol, propranolol, warfarin, among others.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: severe dizziness, very slow heartbeat, new irregular heartbeat, fainting.

Do not share this medication with others.

Lab and/or medical tests (such as EKG) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).