Dofetilide is a heart rhythm medicine, also called an antiarrhythmic.

Dofetilide is used to help keep the heart beating normally in people with certain heart rhythm disorders of the atrium (the upper chambers of the heart that allow blood to flow into the heart). Dofetilide is used in people with atrial fibrillation or atrial flutter.

Dofetilide may also be used for purposes not listed in this medication guide.

You should not take dofetilide if you have severe kidney disease or a history of Long QT syndrome.

Serious drug interactions can occur when certain medicines are used together with dofetilide. Tell each of your healthcare providers about all medicines you use now, and any medicine you start or stop using.

You will need to spend at least 3 days in a hospital setting when you first start taking dofetilide. This is so your heart rhythm and kidney function can be monitored in case the medicine causes serious side effects.

Dofetilide comes as a capsule to take by mouth. It is usually taken twice a day, but may be taken once a day in people with certain conditions. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take dofetilide exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Dofetilide controls abnormal heart rhythms but does not cure them. Continue to take dofetilide even if you feel well. Do not stop taking dofetilide without talking to your doctor.

Dofetilide is available only from a hospital or specialty pharmacy.

You will need to spend at least 3 days in a hospital setting when you first start taking dofetilide. This is so your heart rhythm and kidney function can be monitored in case the medicine causes serious side effects.

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

You may take dofetilide with or without food.

You should not skip doses or stop using dofetilide suddenly. Stopping suddenly may make your condition worse. Follow your doctor's instructions about tapering your dose.

Tell your doctor if you have a prolonged illness that causes severe diarrhea, vomiting, or heavy sweating. These conditions can cause an electrolyte imbalance, making it dangerous for you to use dofetilide.

Your blood pressure will need to be checked often. Your kidney function may also need to be checked with frequent blood tests.

Store at room temperature away from moisture and heat.

You should not take dofetilide if you are allergic to it, or if you have:

• severe kidney disease (or if you are on dialysis); or

• a history of Long QT syndrome.

Some medicines can cause unwanted or dangerous effects when used with dofetilide, and should not be used at the same time. Your doctor may need to change your treatment plan if you use any of the following drugs:

• cimetidine;

• dolutegravir;

• ketoconazole;

• megestrol;

• prochlorperazine;

• trimethoprim (Proloprim, Trimpex, Bactrim, Septra);

• verapamil; or

• a diuretic (water pill) that contains hydrochlorothiazide (HCTZ), such as Accuretic, Aldactazide, Atacand HCT, Benicar HCT, Diovan HCT, Dyazide, Exforge HCT, Hyzaar, Lopressor HCT, Maxzide, Micardis HCT, Monopril HCT, Prinzide, Tekturna HCT, Vaseretic, and others.

To make sure dofetilide is safe for you, tell your doctor if you have:

• heart disease, high blood pressure;

• liver or kidney disease;

• depression, mental illness;

• asthma or allergies;

• any active infection;

• skin problems; or

• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood).

It is not known whether dofetilide will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant while using this medicine.

It is not known whether dofetilide passes into breast milk or if it could harm a nursing baby. You should not breast-feed while you are using dofetilide.

Skip the missed dose and take your next dose at the usual time to stay on schedule. Do not take extra medicine to make up the missed dose.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Talk to your doctor about eating grapefruit or drinking grapefruit juice while taking dofetilide.

Grapefruit and grapefruit juice may interact with dofetilide and lead to unwanted side effects. Discuss the use of grapefruit products with your doctor.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Dofetilide may cause serious side effects. Call your doctor at once if you have:

• headache with chest pain and severe dizziness, fainting, fast or pounding heartbeats;

• loss of appetite, vomiting or severe diarrhea; or

• low magnesium or potassium--confusion, uneven heart rate, increased thirst or urination, sweating, jerking muscle movements, leg discomfort, muscle weakness or limp feeling.

Common side effects of dofetilide may include:

• mild headache;

• mild dizziness; or

• cold symptoms such as stuffy nose, sneezing, sore throat.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Other drugs may interact with dofetilide, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Keep all appointments with your doctor and the laboratory. Your heart rhythm should be checked regularly to determine your response to dofetilide. Your doctor will also want to follow your kidney function and blood level of potassium closely while you are taking dofetilide.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.