At one time or another we’ve all reached for a pain reliever like acetylsalicylic acid (aspirin), or non-steroidal anti-inflammatory drugs (NSAIDs). Here is a look at each, why they are different and how they work.

These over-the-counter medicines treat our headaches, fevers and in the case of aspirin and other NSAIDs inflammation and swelling, which can be associated with injury, infection or diseases such as rheumatory arthritis. We take these drugs for granted, yet it is interesting to see how these drugs were developed, how they work and why are they different.

Aspirin – an ancient NSAID

In the 5th century BC, plant extracts such as willow bark were used to treat fever, pain and inflammation. The extracts were used by Hippocrates to treat the pain that women experienced during labor. The active ingredients in the extracts were salicylates. In the 1800s, synthesized salicylates were used to treat arthritis. A German chemist named Felix Hoffmann further modified this compound. Because his father had arthritis and could not tolerate the stomach irritation caused by his salicylic acid medication Felix Hoffmann synthesize a less acidic compound in the hope that it would cause less stomach irritation. The resulting compound, acetylsalicylic acid, still caused stomach irritation. In 1899 Bayer and Company named it Aspirin. It is also called a NSAID because it stops inflammation, but it is not a steroid.

Now, over 80 billion aspirin tablets are consumed every year in the United States. More than 50 over the counter drugs contain aspirin. While aspirin has many beneficial effects, it also has potentially negative aspects, as we will discuss below. Aspirin’s beneficial properties are that it is an analgesic (relieves mild to moderate pain), an anti-inflammatory drug (decreases swelling with arthritis and minor injuries) and an anti-pyretic (decreases fever).

How does aspirin do all of these important and beneficial functions? It turns out that one of the major things that aspirin can do is stop the function of a protein called cyclooxygenase (COX). There are two types of COX, COX-1 and COX-2. Both types of cyclooxygenase work to take things available in your cell and make them into prostaglandins. Prostaglandins are small molecules that can induce pain, swelling, and fever. They are found at elevated levels at sites of injury and they can tell your nerve cells to send a signal to your brain to make you feel pain. Prostaglandins are also involved in causing muscle cramps during stress and menstruation.

Recently, it has also been found that at certain doses aspirin not only stops COX activity, but also partially stops cells from making factors that increase tissue inflammatory and immune responses. This occurs because proteins involved in switching on the production of the immune factors can’t work. NF-kappa beta is the name of one of the protein switches that doesn’t work well in the presence of aspirin.

In addition to analgesic, anti-inflammatory and anti-pyretic effects, preliminary studies suggest that aspirin can do a lot of other good things. For example, aspirin has been associated with reducing cataracts, increasing blood flow to the gum to reduce gum disease and aspirin is under consideration as a potential chemopreventative agent. Preliminary reports suggest that aspirin use can reduce the incidence of lung, colon and breast cancer. It is also under study in relation to melanoma. Aspirin is known to inhibit the activity of proteins that can in some cases promote cell growth. UV radiation can increase the activity of these proteins in skin cells and aspirin can block this effect in preliminary laboratory studies.

Aspirin is also believed to have positive coronary effects. Prostaglandins are also important for platelet aggregation and clot formation. Inhibiting prostaglandin synthesis can be beneficial if platelet aggregation begins to occur in the presence of significant narrowing of the arteries. If the artery is blocked and it supplies the heart with blood, then a heart attack will result. Several studies have supported this protective effect of aspirin in reducing heart attack. However, clotting is important for stopping bleeding in a major injury. Regular aspirin use has also been associated with a small increase in hemorrhage strokes (bleeding in the brain).

So there are a lot of good things associated with inhibiting prostaglandin synthesis. However, most things our body makes serve some important role. The so-called negative aspects of prostaglandins may actually have some benefit. For example, a low-grade fever may boost our immune function resulting in a shorter period of illness while pain reminds us never to touch a hot pot again. In the stomach, prostaglandins also play a beneficial role. COX-1 produces the prostaglandins that tell the stomach to make mucus. The stomach makes a lot of acid to digest your food, but this acid can also digest your stomach. The mucus is important for protecting your stomach wall from acid injury. Prostaglandins help to decrease acid secretion by the stomach. Because aspirin stops both COX-1 and COX-2 from making prostaglandins, it also results in more acid secretion and less protective mucus coating in the stomach. Both of these factors are conducive to increasing the risk of stomach irritation and ulcers. In fact, it is well accepted that aspirin and other non-steroidal anti-inflammatory drugs can play a major role in the development of ulcers.

In addition to the above functions of prostaglandins, some studies suggest that prostaglandins may be important for bone formation, especially in fracture healing. How prostaglandins work in different tissues is still under investigation but one has to be cautious about the ultimate long-term effects of aspirin intake and its inhibition of prostaglandin production.

Even though aspirin is an over-the-counter drug, one should consult their doctor about frequent or long term use. Aspirin can have serious side effects such as hemorrhage, dizziness and ulcer. In children with viral infections such as flu and chicken pox, aspirin use can lead to a rare but serious brain and liver disorder called Reye syndrome. Also, aspirin use is not recommended for people taking anticoagulants, people with kidney disease or people with asthma. There are also some people who are extremely sensitive to aspirin and cannot tolerate it.

to be continue…

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