Dofetilide is a pure Class III antiarrhythmic that blocks cardiac potassium channels.
It prolongs repolarization and increases refractory period without significant sodium, beta, or calcium channel effects.
• Selectively blocks IKr (rapid delayed rectifier potassium current) • Prolongs Phase 3 repolarization • Prolongs QT interval • Increases action potential duration
Net Effect:
• Suppresses atrial arrhythmias • Maintains sinus rhythm
Unlike Amiodarone, dofetilide has no multi-class effects.
• Rhythm control • Maintenance of sinus rhythm
• Safe in HFrEF • One of few rhythm agents allowed in systolic heart failure
Dofetilide is NOT used for ventricular arrhythmias.
Dofetilide significantly prolongs QT interval.
Risk factors:
• Renal impairment • Hypokalemia • Hypomagnesemia • Concomitant QT-prolonging drugs
QT prolongation is dose-dependent.
Dofetilide must be initiated inpatient.
Requirements:
• Baseline ECG • Continuous telemetry • Serial QT measurements • Renal function assessment • Dose adjustment based on creatinine clearance
This requirement is exam-critical.
• Renally cleared • Requires dose adjustment in CKD • Minimal hepatic metabolism
Renal dosing is essential to reduce torsades risk.
• Baseline prolonged QT • Severe renal impairment • Concomitant QT-prolonging drugs • Electrolyte abnormalities
Avoid with strong CYP3A4 inhibitors.
Amiodarone: • Most effective • Multi-system toxicity • Lower torsades risk
Sotalol: • Beta-blocker + Class III • Also prolongs QT • Renally cleared
Dofetilide: • Pure Class III • Higher torsades risk • Requires inpatient initiation • Safe in HFrEF
✔ Pure potassium channel blocker ✔ Prolongs QT significantly ✔ High torsades risk ✔ MUST be started in hospital ✔ Safe rhythm-control agent in HFrEF
Related:
→ Dysrhythmias Module → Amiodarone → Sotalol → Heart Failure Module → Return to Cardiovascular Modules