Acetaminophen: A Substitute Amide

Often called the aspirin substitute, acetaminophen is the most widely used of all nonpresription pain relievers, accounting for over half of this market. Acetaminophen is a derivative of acetamide in which a hydroxyphenyl group has replaced one of the amide hydrogens.

Acetaminophen is the active ingredient in Tylenol, Datril, Tempra, and Anacin-3. Excedrin, which contains both acetaminophen and aspirin, is a combination pain reliever. Acetaminophen is often used as an aspirin substitute because it has no irritating effect on the intestinal tract and yet has comparable analgesic and antipyretic effects. Unlike aspirin, however, it is not effective against inflamation and is of limited use for the aches and pains of arthritis. Also, acetaminophen does not inhibit platelet aggregation and therefore is not useful for preventing vascular clotting.

Acetaminophen is available in a liquid form that is used extensively for small children and other patients who have difficulty taking solid tablets. The extensive use of acetaminophen for children has a drawback; it is the drug most often involved in childhood poisonings. An overdose of acetaminophen is toxic to the liver.

Acetominophen's mode of action in the body is similar to that of aspirin --- inhibition of protaglandin synthesis.