Welcome to Chemistry Connections, my name is Jayson Shin and I am your host for episode #19 called Advil, Aleve, Tylenol- There’s Chemistry Behind Them All. Today we will be discussing how pain medicines function and what they do to inhibit pain on the molecular level.
When you bruise your elbow, pull a muscle, or just downright feel sick, what’s your number one instinct? Well maybe you’d say ice or taking your temperature, but I’m talking about pain medicine. Pain medicine comes in various forms and products such as Advil, Aleve, and Tylenol just to name a few, but they all have the same function- relieve pain and bring body temperature closer to normal.
So let’s start off with what pain essentially is. It’s the body’s natural response to trauma or imbalance, which we feel as physical pain or discomfort. What happens when a part of the body is injured is a chemical known as prostaglandins are released. These prostaglandins essentially bind with various receptors to stimulate different bodily functions, such as proliferating blood clotting at the site of a contusion. However, these molecules are released as a result of chemical reactions in the body that utilize enzymes known as cyclooxygenase. As we know, enzymes serve to function similar to catalysts in that they can either lower activation energies for reactions or provide quicker, alternative pathways for reactions to produce prostaglandins. Now where pain medicines come in is they bind with the cyclooxygenase enzyme in order to inhibit it from accelerating reactions to produce prostaglandins. As a result, our body’s response to pain is decreased.
Now let’s really think about it. When you first think of pain medicine, you most likely think, “Oh I’ll take a pill and it’ll lower my fever” or “Oh my arm’s gonna feel better after I take a few pills of aspirin.” However, we never know why it works or think about how the pain medicine makes these changes to our bodies. So we’ll look at aspirin for example. You take an aspirin and it kicks in in about 15 minutes, and your symptoms of illness or pain from an injury decrease a bit. How does this happen? Aspirin binds with the enzyme cyclooxygenase in the body. As a result, the enzyme is occupied by a different species, and therefore cannot react with other reactants to produce prostaglandins. Let’s look at what the aspirin actually does to inhibit the production of prostaglandins.
As we all know, enzymes are a form of catalyst that help to proliferate the rate of reaction. In inhibiting the function of enzymes, by occupying them, less substrates are able to reach essential activation energy in order to undergo a reaction and create the prostaglandins products. What occurs in a reaction to produce prostaglandins is the cyclooxygenase enzyme binds with arachidonic acid substrates. As a result, the strength of the arachidonic acid bonds are altered in a way that they become weaker. Therefore, the activation energy required to carry out the reaction is lowered, and more substrates reach sufficient activation energy that way. When these cyclooxygenase enzymes are occupied instead by aspirin molecules, they are unable to accelerate the reaction to produce prostaglandins, and therefore, our body has less of a pain response.
Aspirin’s chemical formula is C9H8O4. At the end of an aspirin molecule, there is an acetyl group with a chemical formula of CH3CO. This portion of the molecule is what bonds to the cyclooxygenase enzyme in order to inhibit it from reacting to produce prostaglandin molecules. Now cyclooxygenase is a large, very complex lipid molecule that consists of a tremendously large carbon chain. What is important to isolate however is the serine group on the molecule, with a chemical formula C3H7NO3. Between the acetyl group on the aspirin molecule and the serine group on the cyclooxygenase molecule, a hydrogen bond is able to be formed. Structurally, there is an OH at the end of the serine molecule and a CO at the end of the acetyl group. The bond occurs between the H on the OH portion of the serine molecule and the O on the CO portion of the acetyl group. Evidently, hydrogen bonds are extremely strong, generally speaking, they are the strongest type of intermolecular force. As a result, the cyclooxygenase is occupied by a different molecule leaving it unable to separate easily and help catalyze the reaction to produce prostaglandins.
So why am I interested in this topic? As an athlete, I’ve faced various injuries through my career, far more than a typical high school baseball player. I’ve had a plethora of pain and have had to take medicine left and right, whether it was Advil, Tylenol, or prescribed drugs following surgery. Freshman year, I had a torn labrum in my shoulder, causing me to miss the entire season and undergo surgery. I had to take pain medicine every day for a month at least to dampen the pain. During my sophomore year of baseball I had rotator cuff impingement in my shoulder making throwing painful. I had to take Advil frequently. In my junior year and senior year, I tore the labrums in both shoulders and I recall taking about 2 advil daily before a game in order to be able to play. From taking so much pain relief medicine, I always wondered how it worked. I had theorized that the medicine possibly produces a reaction to reduce pain, when in fact, it instead lessens the body’s pain response by inhibiting the production of prostaglandins.
Evidently, it is important to understand the true function of pain medicines because we must be aware of what we put inside of our bodies. Any time we put a foreign substance within our bodies, it is always a risk. Therefore, becoming educated on what pain medicines do exactly is imperative to know its safety and proper usage.
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