The chemical compound acetaminophen is an analgesic (a pain killer). It is also known as Paracetamol or in North America by its trade name Tylenol. It relieves headaches and other minor aches and pains and lowers fever. Its chemical formula is C8H9NO2.
Acetaminophen belongs to the class of drugs known as non-steroidal anti-inflammatory drugs (NSAIDs); other members of this class include aspirin and ibuprofen (Advil®). Compared to aspirin, acetaminophen has the advantage of not causing stomach problems, but it doesn't fight inflammation nor does it thin the blood.
Common dosage is 500mg (up to 1000mg) every 4 hours for adults. In high overdoses, acetaminophen causes liver failure and a painful death if untreated; because of the wide over-the-counter availability of the drug, it is often used in suicide attempts.
Acetaminophen should not be taken after alcohol consumption, because the liver, when engaged in alcohol breakdown, cannot properly dispose of acetaminophen.
The patent on acetaminophen has expired (when?) and generic versions of the drug are widely available.
Method of action
Acetaminophen, like the other drugs mentioned above, works by reducing the activity of the cyclooxygenase 2 (COX) enzyme which produces prostaglandins. While the other drugs operate as competitive inhibitors and directly block the active site of COX, acetaminophen blocks COX indirectly; this indirect blockage is effective in brain and endothelial cells but not in platelets and immune cells which have high levels of peroxides. This is the reason that aspirin fights inflammation and acts as a blood thinner while acetaminophen does not.
References:
- Olivier Boutaud et.al., Determinants of the cellular specificity of acetaminophen as an inhibitor of prostaglandin [H.sub.2] synthases, Proceedings of the National Academy of Sciences of the United States, May 14, 2002 v99 i10 p7130(6)