Dofetilide is used to treat an irregular heartbeat (including atrial fibrillation or atrial flutter). It is in a class of medications called antiarrhythmics. It improves your heart rhythm by relaxing an overactive heart.

Side Effects Of Dofetilide

Dofetilide may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

If you experience any of the following symptoms, call your doctor immediately:

  • fast, pounding, or irregular heartbeat
  • rash
  • severe diarrhea
  • dizziness or fainting
  • unusual sweating
  • vomiting
  • loss of appetite
  • increased thirst (drinking more than normal)

Warnings & Precautions

Before taking dofetilide:

  • tell your doctor and pharmacist if you are allergic to dofetilide, any other medications, or any of the ingredients in dofetilide capsules. Ask your pharmacist or check the manufacturer’s patient information for a list of the ingredients.
  • tell your doctor if you are taking cimetidine (Tagamet), dolutegravir (Tivicay), hydrochlorothiazide (Microzide, Oretic), hydrochlorothiazide and triamterene (Dyazide, Maxzide), ketoconazole (Nizoral), megestrol (Megace), prochlorperazine (Compro, Procomp), trimethoprim (Primsol), trimethoprim and sulfamethoxazole (Bactrim, Septra, Sulfatrim), and verapamil (Calan, Covera, Verelan). Your doctor will probably tell you not to take dofetilide if you are taking one or more of these medications.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: amiloride (Midamor); antibiotics such as erythromycin (E.E.S., E-Mycin) and norfloxacin (Noroxin); certain antifungal medications such as fluconazole (Diflucan), itraconazole (Sporanox), and ketoconazole (Nizoral); bepridil (Vascor); cannabinoids such as dronabinol (Marinol), nabilone (Cesamet) or marijuana (cannabis); digoxin (Lanoxin); diltiazem (Cardizem, Cartia XT, Dilacor XR, Taxtia XT, Tiazac); diuretics (‘water pills’); HIV protease inhibitors including atazanavir (Reyataz), darunavir (Prezista), fosamprenavir (Lexiva), indinavir (Crixivan), nelfinavir (Viracept), ritonavir (Norvir, in Kaletra), saquinavir (Invirase) and tipranavir (Aptivus); medications for asthma such as zafirlukast (Accolate); medications for depression, mental illness, or nausea; medications for irregular heart beats such as amiodarone (Cordarone, Pacerone); metformin (Fortamet, Glucophage, Glumetza, Riomet); nefazodone; or quinine (Qualquin).
  • tell your doctor if you have or have ever had long QT syndrome (a condition that increases the risk of developing an irregular heartbeat that may cause fainting or sudden death), or kidney disease.
  • tell your doctor if you have excessive diarrhea, sweating, vomiting, loss of appetite, or decreased thirst or a low level of potassium in your blood, and if you have or have ever had have heart or liver disease.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking dofetilide, call your doctor.

Dofetilide Dosage

Dofetilide comes as a capsule to take by mouth. It is usually taken twice a day but maybe 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.


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.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.