Dofetilide
Antiarrhythmics
Antiarrhythmics
A pure potassium channel blocker that converts and prevents atrial fibrillation. It is started in hospital because it can cause torsades de pointes.
Quick facts
- Group
- Antiarrhythmics
- Target
- hERG potassium channel (IKr)
- Used for
- Conversion of atrial fibrillation
- Key effects
- Headache · Chest pain · Dizziness
- Monitor
- QT or QTc on continuous ECG · Creatinine clearance
- ATC
- C01BD04
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows E-4031, a methanesulfonanilide class III blocker of the same family as dofetilide, in the central cavity of the human hERG channel; no structure with dofetilide bound is available.
Dofetilide blocks the channel that carries the rapid component of the delayed rectifier potassium current (IKr, hERG). Repolarisation slows, the action potential and the effective refractory period lengthen in atria and ventricles, and the QT prolongs in direct relation to dose and plasma level. It has no clinically relevant effect on sodium channels or beta receptors.
- Dofetilide blocks the hERG channel (IKr)
- Repolarisation slows and refractoriness lengthens
- Atrial re-entry stops, but the QT lengthens with the dose
Indications
- Conversion of atrial fibrillation or flutter to sinus rhythm Atrial fibrillation →
- Maintenance of sinus rhythm in highly symptomatic atrial fibrillation or flutter Atrial flutter →
Adverse effects
Common
- Headache
- Chest pain
- Dizziness
Contraindications
- Congenital or acquired long QT syndrome, or a long baseline QT
- Severe kidney impairment
- Use with verapamil, cimetidine, trimethoprim (alone or with sulfamethoxazole), ketoconazole or hydrochlorothiazide
- Hypersensitivity to dofetilide
Key interactions
- Cimetidine, trimethoprim, ketoconazole (block renal cation transport)
- Higher dofetilide levels and torsades; contraindicated
- Verapamil
- Higher dofetilide levels and more torsades; contraindicated
- Hydrochlorothiazide
- Higher dofetilide levels plus low potassium and magnesium; contraindicated
- Potassium-depleting diuretics and other QT-prolonging drugs
- Higher risk of torsades de pointes
What is monitored
- QT or QTc on continuous ECG, before and after doses during initiation
- Creatinine clearance, at baseline and periodically
- Potassium and magnesium
Administration and safety
- Started or restarted only in a facility with continuous ECG monitoring, creatinine clearance calculation and resuscitation, for at least the first days.
- Potassium must be normal before the first dose.
- A missed dose is not doubled; the next dose is taken at the usual time.
Pregnancy and breastfeeding
It harmed fetal growth and survival in rats and mice and human data are lacking, so it is used in pregnancy only if the benefit justifies the risk.
Nursing care
- Record the QTc after doses as ordered and report prolongation at once.
- Check the medicine list for contraindicated drugs, including over-the-counter cimetidine.
- Teach the patient to report fainting, palpitations, vomiting or diarrhoea (risk of low potassium).
Pharmacokinetics
- Absorption
- Nearly complete by mouth, not affected by food or antacids
- Elimination
- Mostly unchanged in urine by glomerular filtration and cationic tubular secretion; clearance falls with kidney function
Test yourself
Think of the answer, then tap the question to see it.
Why is dofetilide started in hospital?
It can cause torsades de pointes, so the QT is monitored continuously and the dose is set by creatinine clearance and QT response.
Which drugs are contraindicated with dofetilide because they raise its levels?
Verapamil, cimetidine, trimethoprim, ketoconazole and hydrochlorothiazide.
Which current does dofetilide block?
The rapid delayed rectifier potassium current IKr (hERG channel).
Connections
← Back to the class: Antiarrhythmics
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - DOFETILIDE capsule (DailyMed (U.S. National Library of Medicine), 2026); Dofetilide: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.