## **Core Concept**
Paracetamol (acetaminophen) poisoning is a common cause of acute liver failure. The mechanism of toxicity involves the formation of a toxic metabolite, N-acetyl-p-benzoquinone imine (NAPQI), which depletes glutathione stores in the liver. The antidote works by replenishing glutathione or directly neutralizing NAPQI.

## **Why the Correct Answer is Right**
The correct answer, **N-acetylcysteine (NAC)**, is an effective antidote for paracetamol poisoning. NAC works by replenishing glutathione stores in the liver, which then binds to and detoxifies NAPQI. Additionally, NAC has a direct detoxifying effect on NAPQI. It is most effective when administered early after ingestion but can still provide benefits even if given later.

## **Why Each Wrong Option is Incorrect**
- **Option A: Vitamin C** - While vitamin C has antioxidant properties, it is not the specific antidote for paracetamol poisoning. Vitamin C does not effectively replenish glutathione or directly neutralize NAPQI in the context of paracetamol overdose.
- **Option B: Penicillamine** - This is a chelating agent used in the treatment of heavy metal poisoning and Wilson's disease, not paracetamol overdose.
- **Option D: S-adenosylmethionine (SAMe)** - Although SAMe has been studied for its potential benefits in liver disease, it is not the standard antidote for acute paracetamol poisoning.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **N-acetylcysteine (NAC)** is the antidote of choice for paracetamol poisoning and works best when given early. A classic regimen involves a loading dose of 150 mg/kg over 60 minutes, followed by 50 mg/kg over 4 hours, and then 100 mg/kg over 16 hours. NAC can also be given orally, but the intravenous route is preferred in acute settings.

## **Correct Answer:** . N-acetylcysteine