• Clinical science

Amiodarone

Abstract

Amiodarone is a class III antiarrhythmic agent that blocks voltage-gated potassium channels. It is used in the treatment of acute ventricular tachycardia and persisting ventricular fibrillation (VF) after unsuccessful defibrillation, as well as the long-term treatment of refractory supraventricular arrhythmia (atrial fibrillation). Since amiodarone has a very low negative inotropic effect, it can be used in patients with a reduced ejection fraction (EF). Side effects commonly involve the thyroid, liver, heart, eyes, and central nervous system. Pulmonary side effects, such as lung fibrosis and chronic interstitial pneumonitis, are rare but severe. Because amiodarone is a cytochrome P450 inhibitor, simultaneous administration of other drugs should be considered carefully to minimize the risk of interactions.

Effects

  • Primary mechanism of action: antiarrhythmic effect via blockage of voltage-gated potassium channels → prolonged repolarization of the cardiac action potential
  • Secondary mechanism of action: inhibits β-receptors and sodium and calcium channels → decreases conduction through the AV and sinus node
  • Special uses: : only antiarrhythmic agent with (almost) no negative inotropic effectuse in patients with reduced EF

References:[1][2]

Side effects

Although amiodarone is an extremely effective antiarrhythmic drug, its side-effect profile limits its use primarily to short-term administration. Amiodarone accumulation in tissues can cause damage to the thyroid, lungs, nerves, skin, eyes, and heart.

Organ system Side effects
Lungs
Thyroid
Liver
Heart
  • Bradycardia and AV block
  • Proarrhythmia
Eyes
GI tract
Skin
  • Photosensitivity
  • Blue discoloration
CNS
  • Various manifestations, esp. peripheral neuropathy (also ataxia, paresthesias, sleep disturbance, impaired memory, and tremor)
GU tract

"Am-IOD-arone" consists of approx. 37% iodine!

References:[3][4]

We list the most important adverse effects. The selection is not exhaustive.

Indications

Amiodarone is the drug of choice for ventricular arrhythmias in most heart failure patients (LVEF < 40%).
References:[5][1][6][7]

Contraindications

References:[8][9]

We list the most important contraindications. The selection is not exhaustive.

Interactions

References:[1][8]

Pharmacokinetics

  • Amiodarone is very lipophilic → accumulation of amiodarone in myocardium and muscles → long duration of action
  • Metabolized in the liver; by CYP3A4 with biliary excretion
Oral treatment IV bolus
Onset of action 2 days to 3 weeks Within a few hours
Time to peak effect 1 week to 5 months 15 minutes
Half-life elimination 40–55 days 9–36 days

References:[8][10]