Amiodarone is a class III antiarrhythmic agent, in that it prolongs both cardiac action potential and refractoriness by blocking potassium currents. It inhibits the voltage-gated potassium channel hERG, also known as KCNH2, with an IC50 value of 1 μM. In addition, amiodarone binds with high affinity to the sigma-1 opioid receptor, 3-β-hydroxysteroid Δ8Δ7 isomerase, and C-8 sterol isomerase (Kis = 1, 25, and 62 nM, respectively) and inhibits human thyroid hormone receptors α and β (IC50s = 0.6, 0.65 μM, respectively). It also inhibits the cytochrome P450 (CYP) isoforms CYP2C8 and CYP3A4 in vitro at low micromolar concentrations.
