Dofetilide drug: quick practical guide

Dofetilide is a prescription antiarrhythmic used to treat atrial fibrillation and atrial flutter. It helps restore and maintain a normal heart rhythm by blocking potassium channels and lengthening cardiac repolarization. Because it can affect the heart’s electrical system, doctors start it with close monitoring.

Who it's for and how it helps: Dofetilide is for adults with atrial fibrillation or atrial flutter when rhythm control is needed. It can convert recent-onset atrial fibrillation back to normal rhythm and lower the chance of recurrence. It won’t fix the underlying cause, but it can improve symptoms like palpitations, shortness of breath, and tiredness.

Important safety points

The main safety issue is QT prolongation and risk of torsades de pointes, a dangerous fast arrhythmia. Because of that, initiation usually happens in hospital with at least three days of ECG monitoring and repeated QT checks. Your doctor will check kidney function first—dofetilide is cleared by the kidneys and doses change based on creatinine clearance. Tell your provider about all other medicines; several drugs raise dofetilide levels or also lengthen the QT interval. Common interacting drugs to avoid include cimetidine, trimethoprim, and verapamil. Also avoid other QT-prolonging drugs like certain antidepressants and some antibiotics.

Dosage, monitoring and what to watch for

Dosing depends on kidney function and weight. Typical starting doses range from 125 to 500 micrograms twice daily, but your doctor will pick the right dose based on tests. Expect an ECG before the first dose, two hours after dosing, and daily while inpatient. Kidney tests are repeated to adjust dose as needed. Stop the drug and seek emergency care if you feel faint, have a sudden fast heartbeat, severe dizziness, or near‑syncope—these can be signs of a serious rhythm problem.

Common side effects include headache, chest discomfort, and lightheadedness. Less common but serious effects include life‑threatening arrhythmias. Do not take dofetilide if you have a baseline long QT, recent heart attack, severe electrolyte imbalance (low potassium or magnesium), or if you are on interacting drugs. Women and older adults may have higher risk from QT effects; providers factor that into decisions.

If you’re thinking about dofetilide, bring a full medication list and recent lab results to your appointment. Ask your clinician how long monitoring will last, when follow-up ECGs are planned, and what symptoms should prompt immediate attention. Dofetilide can be effective, but it requires careful use. With proper monitoring it’s a useful option for many people managing atrial arrhythmias.

If you take dofetilide, keep potassium and magnesium in range —low levels raise risk. Avoid starting new medicines without checking with your cardiologist or pharmacist. Pregnant or breastfeeding? Talk to your doctor; dofetilide needs specialist input. Store the tablets at room temperature away from moisture. If you miss a dose, follow your prescriber's plan; do not double up. Ask before driving if you feel dizzy. Insurance coverage varies—ask pharmacy about costs and patient assistance. Keep follow-up appointments; rhythm medicines need ongoing review. Get emergency help for fainting or palpitations.