Dofetilide

Dofetilide

Dofetilide is a class III antiarrhythmic agent that is prescribed to treat irregular heartbeats, specifically atrial fibrillation and atrial flutter. It is marketed under the brand name Tikosyn by Pfizer, and is available in capsule form.

Pharmacology

Dofetilide works by selectively blocking the rapid component of the delayed rectifier outward potassium current (I_Kr) in the heart. This action prolongs repolarization of the cardiac action potential, which leads to a lengthening of the QT interval on the electrocardiogram. Dofetilide does not affect the inward sodium channel, and it is therefore not classified as a class Ia antiarrhythmic agent.

Clinical Use

Dofetilide is used for the maintenance of sinus rhythm in patients with atrial fibrillation or atrial flutter. It is also used for the conversion of atrial fibrillation and atrial flutter to sinus rhythm. However, it is not effective in converting ventricular tachycardia or ventricular fibrillation to sinus rhythm.

Side Effects

The most serious side effect of dofetilide is Torsades de Pointes, a potentially fatal ventricular arrhythmia. Other side effects include headache, chest pain, and dizziness. Because of the risk of Torsades de Pointes, dofetilide is only available through a restricted distribution program called the TIKOSYN Risk Evaluation and Mitigation Strategy (REMS) Program.

Drug Interactions

Dofetilide is primarily eliminated by the kidneys, and drugs that interfere with renal function can increase the risk of dofetilide toxicity. These include diuretics, ACE inhibitors, and nonsteroidal anti-inflammatory drugs (NSAIDs). Dofetilide should not be used with drugs that prolong the QT interval, such as amiodarone, sotalol, and certain antipsychotics.

See Also

• Antiarrhythmic agent
• Atrial fibrillation
• Atrial flutter
• Torsades de Pointes