Acetaminophen is an oral/IV antipyretic and analgesic drug used to treat fevers and mild to moderate pain. Its exact mechanism is unknown but it is thought to target the cyclooxygenase pathway in the CNS (brain). It does not inhibit the cyclooxygenase pathway in peripheral tissues, an therefore, does not have any peripheral anti-inflammatory effect. The cyclooxygenase (COX) pathway begins in the cytosol with arachidonic acid being formed from membrane phospholipids via phospholipase A2. On the endoplasmic reticulum membrane, arachidonic acid is converted to prostaglandin G2 then to prostaglandin H2 using the enzymes prostaglandin G/H synthase 1 & 2 (COX-1 & COX-2). Prostaglandin H2 leads to the formation of thromboxane A2 (via thromboxane-A synthase), prostacyclin (via prostacyclin synthase) and prostaglandin E2 (via prostaglandin E synthase). Prostaglandin E2 (PGE2) is responsible for mediating pain and fever. Acetaminophen enters the cell through the solute carrier family 22-member 6 transporter and inhibits the COX-1 & COX-2 enzymes on the endoplasmic reticulum membrane. This prevents the production of prostaglandin H2 from arachidonic acid, thereby lowering the concentration of prostaglandin E2 in the cell. Since PGE2 causes pain and fever, reduction of PGE2 would lessen fevers and increase threshold for pain sensation. There are very few side effects associated with acetaminophen, but some people may have allergic reactions which may include itching, rash, difficulty breathing and swelling of face, hands, throat or mouth.

Acetaminophen Pathway (New) References