Amiodarone
also: class III antiarrhythmic
Overview
Broad-spectrum antiarrhythmic for AF, VT/VF and other tachyarrhythmias. Huge volume of distribution, very long half-life (~50+ days), and a long list of organ toxicities.
Mechanism
Predominantly blocks K⁺ channels → prolongs repolarisation and the action-potential duration/refractory period (Class III), but also has Class I (Na⁺), II (β-block) and IV (Ca²⁺) actions. Prolongs QT.
Indications
- AF (rhythm control)
- Ventricular tachycardia / VF (incl. peri-arrest)
- SVT / other refractory tachyarrhythmias
Adverse effects
Both hypo- AND hyperthyroidism (iodine-rich molecule).
Pneumonitis — monitor with baseline CXR/PFTs.
Usually reversible; rarely affect vision.
Cautions & contraindications
Worsens / triggers thyroid dysfunction.
Interactions
- Potentiates warfarin (halve dose, monitor INR)
- Raises digoxin levels (halve dose)
- Other QT-prolonging drugs
- CYP3A4 inhibitor
Monitoring & kinetics
TFTs + LFTs at baseline then 6-monthly,Baseline CXR ± PFTs,U&E, ECG (QT),Annual eye review if visual symptoms
Very long t½ (weeks); loading required; effects persist long after stopping. Give via central line if IV (phlebitis).
Choosing it
true
Source: BNF — Amiodarone