What is the main MOA of Amiodarone?

What is the main MOA of Amiodarone?

• A. Blocks Na+ channels
• B. Blocks Ca2+ channels
• C. Blocks K+ channels
• D. Inhibits beta receptors

Answer: (C)

Amiodarone is best understood as a potassium channel blocker (class III antiarrhythmic). By inhibiting outward K+ currents during repolarization, it slows phase 3 of the cardiac action potential, prolonging both the action potential duration and the effective refractory period. This makes it harder for reentrant circuits to propagate, helping to prevent and terminate tachyarrhythmias. While it does have additional actions—blocking sodium and calcium channels and antagonizing beta receptors—these are supplementary. The dominant mechanism that drives its rhythm control effect is the potassium channel blockade, which is why this action is emphasized as the main MOA.

Amiodarone is best understood as a potassium channel blocker (class III antiarrhythmic). By inhibiting outward K+ currents during repolarization, it slows phase 3 of the cardiac action potential, prolonging both the action potential duration and the effective refractory period. This makes it harder for reentrant circuits to propagate, helping to prevent and terminate tachyarrhythmias.

While it does have additional actions—blocking sodium and calcium channels and antagonizing beta receptors—these are supplementary. The dominant mechanism that drives its rhythm control effect is the potassium channel blockade, which is why this action is emphasized as the main MOA.