Drug Card: Amiodarone

Medication Name: Amiodarone

  • Generic Name: Amiodarone

  • Trade Name(s): Cordarone, Pacerone

Drug Classification: Antiarrhythmic

Description:
Amiodarone is an antiarrhythmic medication used primarily for the treatment of life-threatening ventricular arrhythmias, such as ventricular fibrillation (VF) and ventricular tachycardia (VT). It is also effective for atrial fibrillation (AF) and has a complex pharmacological profile, combining properties from multiple classes of antiarrhythmics, which makes it useful in various cardiac conditions.

Mechanism of Action:
Amiodarone works by prolonging the myocardial cell action potential and refractory period. It inhibits adrenergic stimulation, slows conduction through the AV node, and alters the cardiac membrane's electrical activity, thereby stabilizing the heart rhythm.

Pharmacokinetics:

  • Absorption: Well absorbed orally; however, the bioavailability varies significantly (between 20-50%).

  • Distribution: Highly lipid-soluble, resulting in a large volume of distribution; it accumulates in tissues, particularly in the lungs, liver, and heart.

  • Metabolism: Primarily metabolized by the liver via cytochrome P450 enzymes (CYP3A4).

  • Excretion: Excreted in feces and urine; the half-life can be very long, ranging from days to weeks due to its extensive tissue storage.

Indications/Field Use:

  • Ventricular fibrillation (VF)

  • Ventricular tachycardia (VT)

  • Atrial fibrillation (AF)

Contraindications:

  • Known hypersensitivity to amiodarone

  • Severe bradycardia

  • Heart block (unless a pacemaker is present)

  • Cardiogenic shock

Side Effects/Adverse Reactions:

  • Hypotension

  • Bradycardia

  • Thyroid dysfunction (both hypo- and hyperthyroidism)

  • Pulmonary toxicity (interstitial pneumonitis)

  • Liver toxicity

Dose:

  • Ventricular Fibrillation/Pulseless VT: 300 mg IV push; may repeat with 150 mg if needed.

  • Ventricular Tachycardia with a pulse: 150 mg IV over 10 minutes, followed by an infusion of 1 mg/min for the first 6 hours, then 0.5 mg/min.

Precautions:

  • Monitor cardiac rhythm, blood pressure, and vital signs closely during administration.

  • Consider potential drug interactions, particularly with other antiarrhythmics or anticoagulants.

  • Regularly assess thyroid function and pulmonary status.

Drug-Drug Interactions:

  • May interact with anticoagulants (increasing INR), digoxin (increasing serum levels), and other antiarrhythmics (potentially causing additive effects).

  • Grapefruit juice may increase amiodarone levels by inhibiting its metabolism.