SIDE EFFECTS: 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 persist or worsen, tell your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she 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 any of these rare but very serious side effects occur: signs of infection (such as high fever, severe chills, weakness, persistent sore throat), signs of liver problems (such as persistent nausea/vomiting, 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). Seek immediate medical attention if any of these rare but serious side effects occur: fainting, faster/more irregular heartbeat, severe dizziness. A very serious allergic reaction to this drug is rare. However, seek immediate medical attention 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.

PRECAUTIONS: 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 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. Before having surgery, tell your doctor or dentist that you are using this medication. Older adults may be more sensitive to the side effects of this drug, especially QT prolongation (see above). 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 and may have undesirable effects on a nursing infant. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: 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 clarithromycin, erythromycin), and certain quinolone antibiotics (such as sparfloxacin), among others. (See also Precautions section.) 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, rifampin, and certain HIV protease inhibitors (such as ritonavir, 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, imipramine, metoprolol, propranolol, warfarin, among others.

OVERDOSE: 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 their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe dizziness, very slow heartbeat, new irregular heartbeat, fainting.