How Pain Relievers Work
Inside cells, an enzyme called COX makes substances involved in pain, fever and swelling. Block it with a made-up pain reliever and see what drops, and by how much.
Drug P blocks COX-1 and COX-2 about equally.
Pain-fever-swelling side: 1.00 (without the drug 1.00)
Stomach-protecting side: 1.00 (without the drug 1.00)
Drug P blocks COX-1 and COX-2 about equally. IC50: COX-1 = 2, COX-2 = 2. (0 to 1 scale) without the drug: COX-1 = 1, COX-2 = 1.
blocked share = drug / (drug + IC50); amount made = amount without the drug x (1 - blocked share). IC50 is the drug amount that blocks half; smaller means it blocks better.
With the same dose, the pain-fever-swelling side drops, and the stomach-protecting side drops too. Both come from the same kind of enzyme work, so you cannot trim only one of them.
A drug that treats the two enzymes differently (Drug Q) can be drawn to leave the protecting side less reduced. But this is a made-up drug in a simplified model and does not describe any real drug’s action or side effects.
About other kinds of pain relievers
Some pain relievers are still being researched and their mechanism is not fully understood (for example, the one called acetaminophen). This page does not say they act the same as, or differently from, the drugs in this figure. They are not simulated here.
If you are unsure how to use a medicine, including ones sold without a prescription, ask a pharmacist.
“COX is a factory and the drug blocks its door” is a simplified picture. The inside of a real cell is far more complex.
How to play
Press Auto to raise the amount of Drug P step by step, then Drug Q. Stop and set the drug, amount and body state yourself. Compare how the two amounts change. Every name and number is made up.
Learn more
Cyclooxygenase (COX) is an enzyme that makes substances called prostaglandins from a material called arachidonic acid. Prostaglandins are involved in inflammation, pain and fever. COX comes as COX-1 and COX-2: COX-1 works all the time and supports normal jobs such as protecting the stomach lining, while COX-2 is said to increase during inflammation. The kind of pain reliever called an NSAID (non-steroidal anti-inflammatory drug) blocks COX and so reduces prostaglandin production. How much each drug favours COX-1 or COX-2 differs a little from drug to drug. In 1971 John Vane showed that aspirin-like drugs work by interfering with prostaglandin synthesis, and in 1982 a Nobel Prize in Physiology or Medicine was awarded for work on prostaglandins (aspirin itself had been in use for a very long time).