Amiodarone: Mechanism of Action, Side Effects & Toxicity

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Amiodarone is a drug that can save your life but also threaten it in some cases. In this lesson, find out how this drug works and what side effects it might have.

What Is Amiodarone?

If you were a clever pharmaceutical marketer, what would you name a drug that helps pace the heart? How about Pacerone? The '-one' in Pacerone might have something to do with this drug's chemical structure or it might be a clever way of saying Pacer One, like Air Force One. Who knows?

Anyways, what we do know is that Pacerone is a trade name for amiodarone, a drug that treats various irregular heart rhythms, like ventricular tachycardia. Ventricular tachycardia is a fast ('tachy-') heart ('-cardia') rate that occurs as a result of abnormal electrical activity in the lower and larger chambers of the heart called ventricles.

Let's find out how this drug works as well as what its side effects are in this lesson.

Mechanism of Action

To better understand how amiodarone works, we need to very briefly go over some very basic cardiac electrophysiology. The heart beats thanks to electrochemical signals called action potentials. These action potentials travel and spread through the heart and zap the heart muscle into beating. In between each zap, there's a break, called a refractory period. During the refractory period, an action potential can't zap the heart muscle into beating.

Okay, now that you've got that very basic part down, we can better understand one of the major ways by which amiodarone actually works its magic. Amiodarone works by prolonging the duration of the action potential and the refractory period. This, in effect, minimizes how often the electrical system of the heart can zap the heart muscle into a beat. This results in a lower heart rate.

The second major way by which amiodarone works is by blocking receptors called beta-receptors. When beta-receptors are stimulated by hormones such as epinephrine, your heart starts to beat really fast. So, amiodarone lands on the beta-receptors and tries to prohibit epinephrine from stimulating the heart into beating really fast.

Side Effects and Toxicity

That's all well and good but can too much of a good thing be a bad thing? Of course! And the same goes for amiodarone. In fact, amiodarone is usually limited in its use to people with life-threatening arrhythmias precisely because it has the potential to be toxic!

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