Dofesyn 250 mcg

Indications

Dofetilide is a heart rhythm medicine. It is used to restore and keep a normal heart rhythm (sinus rhythm) in people with atrial fibrillation or atrial flutter, conditions in which the upper chambers of the heart beat fast and irregularly. It is usually chosen for people whose symptoms are troublesome despite other treatment.

How It Works

Dofetilide blocks a potassium channel in heart muscle cells. This lengthens the time each cell needs to recover after a beat (the refractory period), which helps stop the chaotic electrical signals that cause atrial fibrillation and flutter.

Dosage and Administration

Treatment must be started in hospital, with continuous heart monitoring (ECG) for at least 3 days, because the first doses carry the highest risk of a dangerous rhythm. The dose is set by the doctor according to kidney function and the QT interval on the ECG, and is taken as prescribed, usually twice a day, with or without food.

• Do not change the dose or stop the medicine without your doctor's advice.
• If you miss a dose, skip it and take the next one at the usual time. Never take a double dose.
• Regular ECG and kidney blood tests are needed during treatment.

Interactions

Several medicines raise Dofetilide levels and must not be used with it, including Verapamil, Cimetidine, Trimethoprim (alone or with Sulfamethoxazole), Ketoconazole, Prochlorperazine, Megestrol, Dolutegravir and Hydrochlorothiazide. Other medicines that prolong the QT interval, such as some antibiotics (Erythromycin, Clarithromycin), antipsychotics, antidepressants and other antiarrhythmics, increase the risk of serious rhythm problems. Diuretics that lower potassium or magnesium also raise the risk. Tell your doctor about every medicine and supplement you take.

Contraindications

• Allergy to Dofetilide.
• Long QT syndrome or a baseline QT interval that is already prolonged.
• Severe kidney impairment.
• Use with any of the interacting medicines listed above.

Side Effects

Common side effects include headache, chest pain, dizziness, nausea, trouble sleeping and breathlessness. The most serious risk is a dangerous fast heart rhythm called torsade de pointes, which is most likely in the first days of treatment.

Get urgent medical help if you have fainting, a very fast or pounding heartbeat, severe dizziness, chest pain, or signs of allergy such as swelling of the face or difficulty breathing.

Pregnancy and Lactation

There is limited information on use in pregnancy. It should only be used if the doctor decides the benefit clearly outweighs the risk. Breastfeeding is not recommended during treatment.

Precautions and Warnings

Potassium and magnesium levels should be normal before starting and checked during treatment. Tell your doctor if you develop severe diarrhoea, vomiting or heavy sweating, as these can lower potassium. Kidney function and the ECG are rechecked regularly, and the dose may be reduced. Use with care in people with liver disease.

Overdose

An overdose can cause excessive QT prolongation and life-threatening heart rhythms. Seek emergency medical help immediately. Treatment is supportive with continuous heart monitoring in hospital.

Therapeutic Class

Class III antiarrhythmic agent.

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.