Aspirin

Discovery of Aspirin

Active ingredient:

Acetylsalicylic acid

Natural product:

Salicylic acid

Derived from:

Willow tree bark

Salicylic acid

Willow was known as far back at 3000 BC by the Ancient Egyptians and Sumerians as an anti-inflammatory and pain reliever.

In Ancient Greece, Hippocrates used willow bark in tea to reduce fever and pain from childbirth.

The active ingredient, salicylic acid, was isolated for the first time from Willow bark and Meadowsweet flowers, in 1828 in Munich.

1828, a German pharmacist extracted this active ingredient from willow: bitter tasting yellow crystals. He called it 'salicin'.

1853, a French chemist determined the chemical structure of salicylic acid and synthesised acetylsalicylic acid.

1876, clinical trials are conducted on salicylic acid to test it for reduction of fever and joint inflammation.

acetylsalicylic acid

1897, a German chemist working for Bayer finds that adding the acetyl group reduces unwanted side effects.

1899, Bayer names the medicine 'Aspirin'.

1950, Aspirin enters the Guinness World Records for being the most frequently sold painkiller.

Since then, studies have found that acetylsalicylic acid may play a role in reducing the formation of blood clots. Blood clots can cause deadly conditions such as stroke and heart attack if they get stuck and prevent blood from flowing properly.

Now, approximately 10 million Americans take a low dose of aspirin every day.


Click and drag the molecules above to compare their structures.

Acetylsalicylic acid is the same as salicylic acid, except it has an extra acetyl group. It is equally active against reducing pain and inflammation, but has less unwanted side effects than salicylic acid. We can hypothesise that a different part of the molecule is what binds to a protein in the body to have its analgesic effect.

See the website referenced below to learn about the ongoing studies that have been conducted on aspirin.

Salicylic acid

Acetylsalicylic acid

Aspirin:

Anti-inflammatory, analgesic, anti-thrombotic

Aspirin is the trade name for the medicine acetylsalicylic acid.

Aspirin is used to treat pain, fever and inflammation. It is also used to prevent blood clots which can lead to serious conditions like stroke or heart attack. Its main concerning side effect is stomach ulcers.

Like most medicines, aspirin works by binding to receptors in your body. These receptors have an effect on the cell when they are activated. Medicines can be designed to either bind to and block the receptor (we call this an antagonist) or bind to and activate the receptor (we call this an agonist).

Aspirin is an antagonist for the COX enzymes in your body.

Let's look a little more closely at how it works.

In the body, aspirin 'binds' to two different enzymes called COX-1 and COX-2. Aspirin undergoes a chemical reaction with part of the COX enzyme, forming a bond which blocks the COX enzyme. This prevents the molecule which normally binds to and activated COX, arachidonic acid, from binding, and the COX enzymes are permanently switched off. The effect of aspirin lasts as long as it takes for new COX enzymes to be made.

To understand how aspirin has its therapeutic and side effects, we need to understand the normal action of COX-1 and COX-2 in the body.

Both COX enzymes are involve in the body's natural immune response. When COX enzymes are activated, they cause the cells to make:

  • prostaglandin

  • thromboxane

Prostaglandins have the following effects in the body:

  • Produces fever

  • Transmit pain information to the brain

  • In the stomach

      • decrease gastric acid secretion

      • increase gastric mucous secretion

Thromboxanes have the following effects in the body:

  • Causes blood clots to form

When COX enzymes are blocked by acetylsalicylic acid, they prevent these enzymes from playing their role in the normal immune response. When aspirin is present, the body produces:

  • less prostaglandin

  • less thromboxane

Blocking prostaglandin production has the following effects:

  • Reduces fever

  • Prevent some pain information from reaching the brain

  • In the stomach

      • increase gastic acid secretion

      • decrease gastric mucous secretion

Blocking thromboxane production has the following effects:

  • Prevents blood clots from forming