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Chlorhexidine, Iodine & Silver: Uses and Modes of Action

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  • 0:07 Wound Care with Antiseptics
  • 0:48 Iodine and Iodophors
  • 2:54 Silver Compounds
  • 4:23 Chlorhexidine
  • 6:10 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will discuss four commonly heard of chemical antiseptics: namely, iodine and iodophors, silver nitrate, silver sulfadiazine, and chlorhexidine, and it will cover the ways by which they kill microbes.

Wound Care with Antiseptics

For a very long time, people have put all sorts of stuff on cuts, scrapes, and burns to help them heal more quickly. I'm sure you've done this as well when you fell off a bike as a little kid. Everything from alcohol to hydrogen peroxide may have been used, and all of these compounds are known as antiseptics, meaning they are used on living tissue, such as your skin, to try and get rid of as many microbes as possible. Antiseptics can never get rid of all microbes on living tissue, but they try to do their best.

In this lesson, we'll cover a few more compounds used as antiseptics, some of which I'm sure you've heard of.

Iodine and Iodophors

Besides alcohol and hydrogen peroxide, another type of substance sometimes used to clean wounds that you have probably heard of is called iodine. Iodine is a chemical element used in nutrition, medical diagnostic techniques, and antiseptic wound care, among other things.

Our body doesn't make iodine, so we must obtain it from other sources, such as iodine-fortified salt. If we don't get enough iodine, we can develop many conditions, such as goiter, which is essentially an enlarged thyroid gland.

But iodine doesn't need to be ingested with salt in order to exert its beneficial effects. In certain preparations, which can be deadly if ingested in large enough amounts, iodine is used as an antiseptic for wound care. These preparations are sometimes known as a tincture of iodine.

The way by which iodine kills is through the inactivation of protein synthesis and disruption of protein and nucleic acid structure in a microbe.

You can liken the proteins a microbe uses to the little apps on your smartphone and the nucleic acids to the processor of your phone, called the I-odine. If you stop the app makers from making their apps and delete the apps altogether from your phone, or you kill off the processor, then you'll have no use for your smartphone. Likewise, if you destroy the nucleic acids of a microbe or stop them from using and producing their proteins, the microbe will simply die off.

Iodine should not be confused with an iodophor, which is a compound that combines iodine with another compound, such as povidone, to be used as antiseptic or disinfectant. Using an iodophor is usually preferable to iodine alone, as an iodophor allows for the sustained release of iodine, which minimizes the potentially toxic effects of iodine.

Silver Compounds

Another type of antimicrobial agent that may be a bit dangerous to use has been in use in one shape or form for hundreds of years. This agent is called silver. That's right, the same stuff pirates used to fight over is actually used in some preparations as an antimicrobial.

Notably, one preparation is known as silver nitrate. This is a compound that is sometimes used to prevent gonorrheal eye infections in newborns. Ironically, this compound can actually cause more harm than good, as it can damage the eye and, therefore, antibiotics may be used in its stead.

Besides silver nitrate, another well-known, silver-based compound is known as silver sulfadiazine, and it's a topical cream made from a combination of silver and sulfadiazine, a type of antibiotic that is used as an antibacterial agent.

Depending on the preparation it's used in, silver is able to exert its antimicrobial effects by interfering with protein and enzyme function as well as by disrupting the microbe's nucleic acid genome. This is very similar to what iodine does as well. Once again, we basically delete the apps and shut down the processor in our smartphone when we use silver as an antimicrobial agent.

Chlorhexidine

Finally, another type of chemical antiseptic that is used is known as chlorhexidine. It is a chemical antiseptic that is commonly used in hand washing products due to its ability to kill bacteria, some fungi, and certain viruses.

As you can tell by that definition, chlorhexidine isn't a sterilant, meaning it can't kill everything. For example, it isn't effective against hardy bacterial spores or non-enveloped viruses.

The way by which chlorhexidine manages to destroy certain bacteria, viruses, and fungi is actually pretty darn cool. It destroys these microbes by one of two ways.

At low concentrations, it damages the outer and inner membranes of the microbe, which causes the leakage of important substances out of the cell. At high concentrations, it coagulates the cytosol, or the liquid, found inside of the cell. This coagulation inactivates important functions in the cell, resulting in its death.

We can use some real-life examples to demonstrate how chlorhexidine works. At low concentration, it basically pops the cell like a balloon by creating holes in it.

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