How do antiarrhythmic drugs like amiodarone exert their effects?

Antiarrhythmic drugs, such as amiodarone, primarily exert their effects through the blockage of sodium and potassium channels. Amiodarone, in particular, is classified as a class III antiarrhythmic agent, but it has properties that span multiple classes. Its ability to block potassium channels extends the action potential duration and refractory period of cardiac tissue, which helps to stabilize heart rhythms.

In addition to potassium channel blockade, amiodarone also possesses sodium channel blocking activity, especially at higher heart rates. This provides further stabilization of the cardiac membrane potential and aids in controlling abnormal heart rhythms. Together, these mechanisms contribute to amiodarone's effectiveness in managing various types of arrhythmias, including atrial fibrillation and ventricular tachycardia.

While options relating to enhancing intracellular calcium levels or activating beta-adrenergic receptors pertain to different pharmacological actions and are relevant in the context of other drug classes, they do not describe the primary action of amiodarone and similar antiarrhythmic agents. Increasing heart rate is not a mechanism by which amiodarone operates; rather, it serves to modify and often decrease the rate of abnormal electrical activity in the heart.