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Ibutilide

  • AntiarrhythmicsAntiarrhythmics
  • High alertAn error with this medicine can cause serious harm: double checks and protocols are used.

An intravenous class III drug for rapid conversion of recent-onset atrial fibrillation or flutter. Torsades de pointes is its main danger.

Updated

Quick facts

Group
Antiarrhythmics
Target
Cardiac repolarising currents (slow inward sodium current and hERG/IKr)
Used for
Rapid conversion · Rapid conversion
Key effects
Headache · Nausea · Hypotension
Monitor
Continuous ECG during the infusion · Blood pressure
ATC
C01BD05

No doses: the clinician sets them by the current guideline.

Mechanism of action

Ibutilide lengthens the action potential and refractoriness of atria and ventricles (class III effect). Its label describes delayed repolarisation mainly through activation of a slow inward, largely sodium, current; it also blocks IKr. It slightly slows the sinus rate and AV conduction and does not widen the QRS.

  1. Ibutilide delays repolarisation in atria and ventricles
  2. Refractoriness lengthens and the atrial re-entry stops
  3. The QT prolongs: risk of torsades during and after the infusion

Indications

Adverse effects

Common

  • Headache
  • Nausea
  • Hypotension
  • Bradycardia and bundle branch block

Contraindications

  • Hypersensitivity to ibutilide or other components

Key interactions

Class IA (disopyramide, quinidine, procainamide) and other class III drugs (amiodarone, sotalol)
Additive prolongation of refractoriness; not given together or shortly after the infusion
Phenothiazines, tricyclic and tetracyclic antidepressants, some H1 antihistamines
Higher risk of torsades through QT prolongation

What is monitored

  • Continuous ECG during the infusion and for hours afterwards, until the QTc returns to baseline
  • Potassium and magnesium before treatment
  • Blood pressure

Administration and safety

  • Given as a short intravenous infusion with continuous ECG monitoring; a defibrillator, pacing and drugs for polymorphic VT are at hand.
  • The infusion is stopped as soon as the arrhythmia ends, or if VT or marked QT prolongation appears.
  • Low potassium and magnesium are corrected before starting.

Pregnancy and breastfeeding

It was teratogenic and embryocidal in rats; it is used in pregnancy only if the benefit clearly justifies the risk.

Nursing care

  • Stay with the patient and watch the monitor throughout the infusion.
  • Keep the ECG running after the infusion until the QTc is back to baseline, longer if arrhythmias appear.
  • Check that other antiarrhythmics are held as ordered.

Pharmacokinetics

Distribution
Large volume of distribution; levels fall rapidly after the infusion
Metabolism
Liver, by oxidation of its side chain; kinetics vary widely between people
Onset and duration
Conversion, when it happens, usually occurs during or soon after the infusion

Test yourself

Think of the answer, then tap the question to see it.

For which arrhythmias is intravenous ibutilide used?

Rapid conversion of recent-onset atrial fibrillation or atrial flutter to sinus rhythm.

How long is the ECG monitored after an ibutilide infusion?

Continuously for several hours, until the QTc returns to baseline, and longer if arrhythmias appear.

What is corrected before giving ibutilide, and why?

Low potassium and magnesium, to reduce the risk of torsades de pointes.

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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 - IBUTILIDE FUMARATE injection, solution (DailyMed (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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