Amiodarone is a class III antiarrhythmic, along with ibutilide, dofetilide, sotalol, and dronedarone. Class III antiarrhythmic drugs work by slowing repolarization via potassium channel blockade.
Amiodarone decreases sinoatrial (SA) node automaticity and atrioventricular (AV) node conduction velocity (via calcium channel and beta-receptor blockade). This prolongs the refractory period (via potassium and sodium channel blockade) and inhibits ectopic pacemaker automaticity.
Amiodarone inhibits metabolism through various cytochrome P450 pathways, including CYP2D6, -3A4, and -2C9. Cytochrome P450 enzymes are essential for metabolizing some medications. If this enzyme is inhibited, the concentration of those medications in the blood will increase, potentially leading to toxicity.
Amiodarone can be used to treat supraventricular tachycardia (SVT) e.g. atrial fibrillation in the context of heart failure. It is effective in hemodynamically unstable patients and patients with congestive heart failure with decreased left ventricular ejection fraction, which may be untreatable with other rhythm-control medications.
Intravenous amiodarone is effective in treating ventricular tachyarrhythmias. These includes ventricular tachycardia, pulseless ventricular fibrillation and ventricular tachycardia which is refractory to cardiopulmonary resuscitation (CPR), defibrillation, and epinephrine administration.
Hepatotoxicity is characterized by the increase of hepatic enzyme levels (e.g. AST, ALT) and is often asymptomatic. Reduction and/or discontinuation of the dosage can be considered if the elevation exceeds double or three times normal.
Pulmonary fibrosis can be a side effect of amiodarone in 5-7% of patients. It can manifest with hypoxemia, dyspnea, and exertional desaturation.
Bradycardia can occur in 2-4% of patients being treated with amiodarone. It occurs due to the mechanism of amiodarone i.e. decreasing SA node automaticity and AV node conduction velocity.
Heart block can occur with intravenous amiodarone administration. Amiodarone is contraindicated in second- or third-degree heart block patients who do not have a pacemaker.
Amiodarone contains an iodine component (40% iodine by weight), which has a similar structure to thyroxine and affects the thyroid gland. Hypothyroidism (2% cases) or hyperthyroidism (6% cases) can occur. If a new arrhythmia is found in a patient being treated with amiodarone, hyperthyroidism should be suspected.
Dermatologic side effects can occur with amiodarone administration. Blue-gray skin deposits ("smurf-skin") can be seen in close to 9% of patients. It is usually seen in exposed skin. Another finding is photosensitivity (10% cases) which can be prevented by Sun barrier creams or protective clothing.
Corneal deposits often occur in patients (up to 90% cases) using amiodarone. It can be seen by slit-lamp examination. Once amiodarone is in the blood, it may start to be secreted by the lacrimal glands and then uptaken by corneal epithelium. Patients may complain of visual halos or blurred vision.
Picmonic's rapid review multiple-choice quiz allows you to assess your knowledge.
*Average video play time: 2-3 minutes
Unforgettable characters with concise but impactful videos (2-4 min each)