What medication serves as the antidote for acetaminophen overdose?

N-acetylcysteine is the antidote for acetaminophen overdose because it replenishes glutathione stores, which are depleted by the toxic metabolites of acetaminophen. When acetaminophen is ingested in large amounts, it gets metabolized to a harmful compound that can cause liver damage. N-acetylcysteine works by restoring the levels of glutathione, allowing for safer metabolism and excretion of the toxic byproducts, thereby mitigating the risk of acute liver failure.

Activated charcoal can be used to reduce the absorption of acetaminophen if administered shortly after the overdose, but it does not counteract the effects of the toxic metabolites already present in the body. Flumazenil is a benzodiazepine antagonist and is not relevant in the context of acetaminophen toxicity, while atropine is an anticholinergic agent used primarily in cases of poisoning with cholinergic agents and does not play a role in acetaminophen overdose treatment.