How Does Aspirin Kill Pain?

Salicylic Acid

Aspirin is a derivative of salicylic acid, a chemical found in the white willow plant. Used by generations of people before modern medicine, white willow bark was known to reduce fever and swelling. Scientists worked for many years to reproduce the same kind of properties in a synthetic drug. In the early twentieth century, research laboratories began manufacturing aspirin (generically known as acetylsalicylic acid), and widespread consumer distribution began.

Benefits of Aspirin

The benefits of taking aspirin reach beyond its pain-killing abilities. A low, daily dose of aspirin acts as a blood thinner when it reduces the production of thromboxane, the agent that makes platelets stick together. Because of this action, aspirin reduces the risk of heart attack and stroke. Aspirin is also used in rheumatoid arthritis and gout cases because of the drug's anti-inflammatory properties. Before non-steroidal anti-inflammatory drugs were developed, aspirin was used to treat fever, especially in children. In most cases, aspirin is taken to reduce pain.

Prostaglandin Production

Aspirin works because it inhibits the production of prostaglandins. The human body contains many different kinds of prostaglandins--each one is used in a different way and in a different area. Prostaglandins are unsaturated, fatty acids secreted by various cells used in the immune response, which is stimulated by the central nervous system. Prostaglandins cause pain and inflammation in and around injuries and wounds. When secreted by the hypothalamus, prostaglandins increase body temperature, causing fever. These are normal responses produced by the body to promote healing and immunity.

Side Effects of Prostaglandins

Although the body is working to keep itself healthy by producing prostaglandins, the resulting symptoms are uncomfortable. Aspirin inhibits prostaglandin production by restraining actions of the COX-2 enzyme. Without this enzyme, prostaglandins cannot be produced. This stops pain, fever and swelling.

Enzymes

Enzymes are proteins that produce chemical reactions within cells. In this capacity, enzymes are called catalysts, because they enable a certain response. In this case, the chemical reaction is the response. COX-2 enzymes work to produce the prostaglandins involved in immunity and trauma response. Taking aspirin inactivates COX-2 enzyme production and without COX-2 enzymes, prostaglandins do not operate in their full capacity.

Negative Effects of Aspirin Use

The downside of using aspirin is that there are prostaglandins produced to protect the stomach. These prostaglandins regulate stomach acid and mucous production, thereby keeping a healthy balance between the two. COX-1 enzymes associated with prostaglandin production in the stomach. When these prostaglandins are suppressed, that healthy balance is thrown off kilter. This is why excessive aspirin use causes irritation of the stomach lining, ulcers and bleeding.