WARNING: THIS MEDICINE SHOULD NOT BE USED in patients with severe (class IV) heart failure. It should also not be used in patients with heart failure who have recently had worsening symptoms that required hospitalization. The risk of death may be increased in these patients. THIS MEDICINE SHOULD NOT BE USED in patients with a certain type of irregular heartbeat called permanent atrial fibrillation. The risk of death, stroke, and hospitalization for heart failure may be increased in these patients. Some medicines or medical conditions may interact with this medicine. INFORM YOUR DOCTOR OR PHARMACIST of all prescription and over-the-counter medicine that you are taking. DO NOT TAKE THIS MEDICINE if you are also taking carbamazepine, hydantoins (eg, phenytoin), phenobarbital, primidone, rifamycins (eg, rifampin), or St. John's wort. DO NOT TAKE THIS MEDICINE if you are also taking another antiarrhythmic (eg, amiodarone, dofetilide, flecainide, sotalol), asenapine, certain azole antifungals (eg, ketoconazole, itraconazole, voriconazole), citalopram, clozapine, cobicistat, cyclosporine, fingolimod, halofantrine, haloperidol, macrolide antibiotics (eg, erythromycin, clarithromycin), maprotiline, nefazodone, nilotinib, ondansetron, paliperidone, phenothiazines (eg, thioridazine), protease inhibitors (eg, boceprevir, ritonavir), quetiapine, telithromycin, tetrabenazine, tricyclic antidepressants (eg, amitriptyline), vardenafil, or any other medicine that may increase the risk of a certain type of irregular heartbeat (prolonged QT interval). Check with your doctor or pharmacist if you are unsure if any of your medicines may increase the risk of this type of irregular heartbeat. ADDITIONAL MONITORING OF YOUR DOSE OR CONDITION may be needed if you are taking other prescription or nonprescription medicines (eg, used for allergies, blood thinning, cancer, chest pain, depression or other mental or mood problems, drug or other substance abuse or dependence, heartburn, hepatitis C, high blood pressure, high cholesterol, HIV, immune system suppression, infections, irregular heartbeat or other heart problems, multiple sclerosis, nausea and vomiting, pain, seizures, swelling or fluid retention, Tourette syndrome), multivitamin products, or herbal or dietary supplements (eg, herbal teas, coenzyme Q10, garlic, ginseng, ginkgo). Ask your doctor or pharmacist if you are unsure if any of your medicines might interact with this medicine. DO NOT START OR STOP any medicine without doctor or pharmacist approval. Inform your doctor of any other medical conditions, including a history of other heart problems (eg, heart failure, irregular heartbeat other than atrial fibrillation), electrolyte problems (eg, low blood potassium or magnesium), liver problems, kidney problems, allergies, pregnancy or if you are able to become pregnant, or breast-feeding. USE OF THIS MEDICINE IS NOT RECOMMENDED if you have permanent atrial fibrillation (atrial fibrillation that will not or cannot be changed back to a regular heartbeat); you have severe (class IV) heart failure; you have heart failure and have recently had worsening symptoms that required hospitalization; you have second- or third-degree heart block or sick sinus syndrome, unless you have a pacemaker; you have a very slow heartbeat or certain other types of irregular heartbeat; or you have severe liver problems. USE OF THIS MEDICINE IS NOT RECOMMENDED if you have developed liver or lung problems after using another antiarrhythmic medicine called amiodarone. USE OF THIS MEDICINE IS NOT RECOMMENDED if you are pregnant, may become pregnant, or are breast-feeding. Contact your doctor or pharmacist if you have any questions about taking this medicine.