Nitroglycerin Mechanism of Action

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson covers a medication called nitroglycerin. First you'll learn its most important use, then you'll learn the basic anatomy and physiology of blood vessels. Finally, you'll tie that into nitroglycerin's mechanism of action and how it treats chest pain.

Multi-Use Chemical Substances

So you know how we use rat poison to treat people? Seriously, we do! There is a medication called warfarin that is used to save people's lives by thinning their blood. It's also used to kill rats. Well, there's one medication even cooler than that. It, like warfarin, is used to save human lives. But it was originally used to make dynamite!

That medication is called nitroglycerin. You'll learn a bit about it and its mechanism of action in this lesson.

The Basics of Nitroglycerin

Nitroglycerin is, shortly put, a vasodilator. A vasodilator is a compound that expands blood vessels. 'Vaso-' means blood vessel and '-dilator' is something that dilates or expands something. In this case it expands blood vessels. Nitroglycerin's main use is to prevent something called angina pectoris, or chest pain.

Basic Blood Vessel Anatomy & Function

In order to understand how nitroglycerin accomplishes this feat, we must briefly go over some very basic but important blood vessel anatomy and function. Don't worry, this won't take long!

You have blood vessels called veins and arteries that carry blood around your body. Arteries take oxygenated blood from the heart and deliver it to tissues (including the muscle of the heart). Veins take deoxygenated blood and carry it back to the heart.

A blood vessel is like a pipe. It has a wall and it has a center, called the lumen. The center of a pipe is filled with water but the center of a blood vessel is filled with blood. Unlike a rigid metal pipe, however, a blood vessel is somewhat flexible. It can expand (dilate) or it can contract (constrict).

It does so thanks to a kind of muscle, called vascular smooth muscle. The blood vessels of your body have a muscular layer to their wall. When the muscles of this layer tighten, the blood vessel narrows and blood has a harder time getting through. When these muscles relax, the blood vessel expands and the blood flows more freely through the blood vessel.

Mechanism Of Action

Remember, the main use of nitroglycerin in medicine is for the relief of chest pain. Why does chest pain occur? Well, there are actually many reasons for chest pain, but from this lesson's perspective the chest pain occurs because of the fact that the heart isn't getting enough oxygen to do its job, that of pumping blood around the body.

Have you ever run around so much that your leg muscles began to hurt and you had to stop? One reason for that leg muscle pain and cramping is a lack of an adequate supply of oxygenated blood to the leg muscles. Same thing with the heart! It needs lots of oxygenated blood to work pain-free.

How can we help the heart out and thus reduce its pain? One of two ways. We can either ensure it gets more oxygenated blood for its high workload or we can decrease its workload so it doesn't have to use so much oxygen in the first place! Nitroglycerin works by doing both, albeit its main mechanism of action is focused on decreasing the workload and thus decreasing oxygen demand.

Here's what happens. A person is given nitroglycerin. The medication enters the vascular smooth muscle. Here, nitroglycerin helps form a compound called nitric oxide. Through a series of steps and reactions, the nitric oxide causes the relaxation of the smooth muscle cells and thus the vasodilation of the veins and arteries.

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