How Does
Alka-Seltzer
®
Work?

The familiar plop, plop, fizz, fizz you hear when you drop Alka-Seltzer into water is the key to its speedy relief. Alka-Seltzer has a unique chemical formula that explains its dual role as an antacid and analgesic. Because Alka-Seltzer is already in solution when you take it, it is absorbed quickly. This means you get rapid relief from your headache and heartburn, acid indigestion or sour stomach.

Each Alka-Seltzer tablet contains:

  • Acetylsalicylic acid (ASA), commonly known as aspirin
  • Citric acid
  • Sodium bicarbonate.

When the tablet is dropped into water, its effervescence causes rapid disintegration. A series of chemical reactions results principally in the following substances:

  • Sodium citrate (antacid)
  • Sodium acetylsalicylate (pain reliever)

The sodium acetylsalicylate acts as the pain reliever and the sodium citrate is the antacid.

Sodium Citrate

Sodium citrate is a medically proven substance for neutralizing acid. In soluble form it works as a buffer substance. Adding a buffer to gastric juice lowers the concentration of acid in the gastric juice. Substances that do this are called antacids.

The sodium citrate in Alka-Seltzer provides fast relief for an upset stomach by neutralizing the stomach acid and it helps the pain reliever rapidly reach the small intestine where it can be absorbed more quickly. This process helps protect the stomach wall and it allows for faster absorption of the pain reliever (sodium acetylsalicylate).

Sodium Acetylsalicylate

While sodium citrate relieves heartburn by neutralizing acid, sodium acetylsalicylate is the pain reliever in Alka-Seltzer.

While plain aspirin is acetylsalicylic acid, Alka-Seltzer solution provides the sodium salt, or sodium acetylsalicylate. This compound is completely soluble in water, but insoluble in fat, and is highly ionized. These features allow sodium acetylsalicylate to remain in solution and be absorbed in the small intestine. After absorption, however, it provides the same relief as aspirin.

The advantages of taking Alka-Seltzer in solution:

 

Whew! Now that you know all of the science behind the workings of Alka-Seltzer, experience its speedy relief with a free sample of new Alka-Seltzer Cherry Flavor! And, don't forget to try our science experiments, which help explain the chemical properties of Alka-Seltzer.

Have more questions about Alka-Seltzer? See our Frequently Asked Questions.

* Advil is a registered trademark of Whitehall Laboratories. Tylenol is a registered trademark of McNeil Consumer Products Co.

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