What is the mechanism of action of acetaminophen?

• A. Blocks histamine receptors.
• B. Binds to beta-adrenergic receptors.
• C. Stimulates pain receptors.
• D. Inhibits prostaglandin production.

Answer: (D)

Prostaglandins amplify pain signals and raise the body's temperature set point during fever. Acetaminophen works mainly in the brain to reduce prostaglandin production, which dampens how pain is perceived and lowers fever. Because its effect is centered in the CNS and it doesn’t strongly suppress prostaglandin production in peripheral tissues, it has little anti-inflammatory action—unlike NSAIDs that reduce inflammation in the body. The other ideas describe actions of drug classes that don’t match how acetaminophen works: blocking histamine receptors would be antihistamines; binding to beta-adrenergic receptors describes beta-blockers; stimulating pain receptors would increase pain signals.