What is the antidote for acetaminophen toxicity?

• A. Acetylcysteine
• B. Flumazenil
• C. Naloxone
• D. Vitamin K

Answer: (A)

Acetaminophen toxicity damages the liver because the reactive metabolite NAPQI is formed in excess when glutathione is depleted. Acetylcysteine works by replenishing hepatic glutathione stores and providing a sulfhydryl group that helps detoxify NAPQI, preventing hepatocellular injury and reducing the risk of liver failure. Early administration is crucial—the sooner acetylcysteine is given after overdose, the better the protection, with benefit still possible even if started later, though outcomes worsen with delays. In practice, acetaminophen levels plotted against time since ingestion guide treatment decisions using a nomogram, and crossing the treatment line indicates the need for acetylcysteine. The other drugs mentioned are not antidotes for acetaminophen toxicity: one reverses benzodiazepines, another reverses opioids, and the last addresses vitamin K–related coagulation issues, not acetaminophen-induced liver injury.