Small molecule
PubChem CID 2157
Amiodarone
Pacerone
- Mechanism of action
- Class III antiarrhythmic, blocks potassium channels to prolong cardiac repolarization
- In plain language
- Blocks several of the heart muscle's electrical channels at once, most notably potassium channels, which lengthens the heart's electrical reset time between beats and calms down dangerous, fast, chaotic heart rhythms — though this same power over the heart's electrical system comes with a real risk of serious side effects to the lungs, liver, and heart itself.
- How it works
- Amiodarone (Pacerone) is classified as a class III antiarrhythmic, though per the FDA label it possesses electrophysiologic characteristics of all four Vaughan Williams classes. Its main effect with prolonged administration is to lengthen the cardiac action potential (a class III effect) by blocking myocardial potassium channels, slowing conduction and prolonging refractoriness. Its antisympathetic and calcium/potassium channel-blocking actions also produce negative dromotropic effects on the sinus and atrioventricular nodes. These combined effects prolong the refractory period in all cardiac tissues and generally reduce automaticity, which suppresses the reentrant and ectopic circuits that drive life-threatening ventricular arrhythmias.
- Therapeutic applications
- Pacerone (amiodarone) carries an FDA boxed warning for pulmonary, hepatic, and cardiac (proarrhythmic) toxicity: the label states it should be reserved for patients with the indicated life-threatening arrhythmias because its use is accompanied by substantial toxicity, some also life-threatening, and that alternative agents should be tried first. Within that constraint, amiodarone is FDA-indicated for recurrent ventricular fibrillation and recurrent hemodynamically unstable ventricular tachycardia. Reported pulmonary toxicity (hypersensitivity pneumonitis or interstitial/alveolar pneumonitis) has reached clinically manifest rates as high as 17% in some patient series.
- Class
- Small molecule
- Therapeutic area
- Cardiovascular
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