Miracle Pill: Aspirin – how does it work?


Aspirin goes by many names: Bayer Aspirin, Ecotrin, acetylsalicylic acid, etc. It’s acknowledged everywhere as the go-to pill for headaches and pain.

Long ago, Hippocrates noted that willow bark powder can ease pain. The compound, known as salicin, reverts to salicylic acid in the body. Despite effective pain management, salicylic acid is highly corrosive, especially to stomach mucous linings.

Structure of salicylic acid, a plant hormone derived from willow bark

Structure of salicylic acid, a plant hormone derived from willow bark

In the late nineteenth century, German chemist Felix Hoffman at Friedrich Bayer & Co. conjugated a less reactive acetyl group to the acidic hydroxyl of salicylic acid, postulating that the less acidic derivative would be less damaging to stomach lining. Acetylsalicylic acid proved potent in pain reduction and less damaging to the gastrointestinal tract and earned a new name, Aspirin.

Structure of acetylsalicyclic acid, aka Aspirin

Structure of acetylsalicyclic acid, aka Aspirin

Pain is mediated in part by prostaglandins, lipid derived compounds created by the activity of cyclooxygenase 2 (COX-2) in response to tissue damage. Prostaglandins in part trigger inflammation and mediate the nervous signal for pain.

Acetylsalicylic acid is a irreversible inhibitor of COX-2. By covalently bonding to the enzyme, Aspirin prevents COX-2 from producing prostaglandins, thus reducing the pain response and inflammation that typically results.

Structure of COX-2, aka Prostaglandin Synthase-2, in complex with an inhibitor

Structure of COX-2, aka Prostaglandin Synthase-2, in complex with an inhibitor

Aspirin is water-miscible, and can travel in the bloodstream throughout the entire body to inhibit prostaglandin production. The liver metabolizes salicylic acid and conjugates groups to it for the kidneys to filter and excrete in urine. Metabolism takes 4-6 hours, after which another pill will be ingested.

Unfortunately, Aspirin is a nonselective inhibitor: it also deactivates COX-1 which functions to maintain the stomach lining. COX-1 inhibition explains Aspirin’s most notable side effect, stomach irritation. Preventing the stomach lining from replenishing wears down the protective lining and renders the stomach vulnerable to stomach acid. COX-1 inhibition is the reason salicylic acid is also damaging to stomach lining, not the acidity as Hoffmann postulated.

Aspirin is an NSAID, non-steroidal anti-inflammatory drug, joining the ranks of ibuprofen and naproxen, commonly employed to treat pain welling, and fever. In addition, Aspirin specifically slows down clot formation that might have contributed to heart attachs, blood vessel clotting, and cardiovascular disease.



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3 Responses

  1. December 24, 2012

    […] research and accumulating evidence has shown that nonsteroidal anti-inflammatory drugs (NSAIDs) have a shot in the battle against cancer. Recent experiments show that NSAIDs stimulate cell […]

  2. December 28, 2012

    […] drugs, and infection exacerbate the disease. Treatment includes intravenously administered hematin, pain medication, sedatives, blood removal, and a number of dietary […]

  3. January 22, 2013

    […] Ibuprofen is an anti-inflammatory drug used for pain relief, headaches, swelling reduction, and fevers. It also might cure cancer. Ibuprofen also goes by Advil, Brufen, Motrin, and Nurofen (or for chemists, (RS)-2-(4-(2-methylpropyl)phenyl)propanoic acid). Here’s some more facts on NSAIDS. […]

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