Tylenol is the brand name for acetaminophen, which is an analgesic and antifever medicine. It is one of the most widely sold over-the-counter medicines in the world. Although it is categorized as a nonsteroidal anti-inflammatory drug (NSAID), Tylenol does not have anti-inflammatory properties.
Tylenol works by blocking the production of prostaglandins in the body. Prostaglandins are molecules that the body releases during inflammatory or infectious events. When the body detects an infection or an inflammatory trigger, it releases substances called interleukins, which help draw cells involved in the immune defense of the body to the site of injury or infection. These cells then further release other compounds, called pyrogenic cytokines, which in turn go to the different tissues and stimulate the production of prostaglandins. The prostaglandins then travel to the hypothalamus in the brain. In response to the elevation of the levels of prostaglandins, the hypothalamus elevates the body's temperature set point, producing fever. The fever in turn helps the body fight off infections or helps signal that an inflammatory process is underway.
Tylenol's Effect on Fever
Tylenol, and other drugs like it, reduce fever by decreasing the amount of prostaglandin produced by the hypothalamus. It does so by inhibiting the function of an enzyme called cyclo-oxygenase, which is critical in the production of prostaglandins. When this enzyme is inhibited, the level of prostaglandin falls, and the body returns to its baseline set point.
Tylenol's Effect on Pain
Tylenol also reduces pain, although its exact mechanism of action is not known. It is thought that it increases the body's pain threshold, therefore enabling a person taking it to tolerate levels of pain that he would not tolerate without taking acetaminophen.
Even though it is an over-the-counter medicine, Tylenol can be a dangerous medicine. Excessive doses of Tylenol (either in the acute setting or in chronic ingestion) can cause significant liver toxicity. The liver metabolizes Tylenol, and an overdose of Tylenol can rapidly deplete the enzymes involved in its metabolism, resulting in significant liver damage. In these cases, a drug called acetylcysteine is administered to the patient to limit the damage to the liver. In excessive doses, the damage to the liver is so extensive that only a liver transplantation can save the patient