dofetilid

Dofetilide is an antiarrhythmic medication in the class III category. It acts as a pure blocker of the cardiac rapidly activating delayed rectifier potassium current (Ikr) through the hERG potassium channel, leading to prolonged repolarization and an extended QT interval on the electrocardiogram. Clinically, dofetilide is used to maintain sinus rhythm in adults with atrial fibrillation or atrial flutter after conversion to normal rhythm.

Initiation and monitoring are distinctive for this drug because of the risk of QT prolongation and torsades de pointes. In many settings, dofetilide initiation requires inpatient, monitored administration with continuous ECG telemetry for several days, alongside assessment of renal function and electrolyte levels. Dosing is adjusted based on renal function, baseline QTc, and subsequent ECG responses; repeat ECGs are used to determine whether dose adjustments are needed. The drug is administered orally and has a substantial renal clearance component, with a longer half-life in patients with impaired renal function.

Safety and interactions are important considerations. Common adverse effects include headache and dizziness, while serious risks include torsades de pointes and QT prolongation, particularly in the presence of electrolyte disturbances or other QT-prolonging drugs. Potential drug interactions include medications that increase dofetilide levels or prolong the QT interval, such as certain antibiotics and other antiarrhythmics, as well as drugs that affect renal excretion.

Contraindications include congenital or acquired long QT syndrome, significant bradycardia, and severe renal impairment (with creatinine clearance limits). Dofetilide is sold under the brand name Tikosyn and is available in generic forms; its use requires careful patient selection, monitoring, and adherence to renal-dose protocols.