**Core Concept**
N-Acetylcysteine (NAC) is the primary antidote for paracetamol (acetaminophen) poisoning, acting as a glutathione precursor to replenish reduced glutathione levels in the liver and mitigate liver damage.

**Why the Correct Answer is Right**
Paracetamol is metabolized to N-acetyl-p-benzoquinone imine (NAPQI), a toxic metabolite that depletes glutathione stores. NAC replenishes glutathione, facilitating the conjugation of NAPQI and reducing liver injury. The standard treatment involves administering NAC within 8-10 hours of ingestion, with a loading dose of 150mg/kg followed by a 5-hour infusion of 100mg/kg.

**Why Each Wrong Option is Incorrect**
**Option A:** Activated charcoal is not effective in treating paracetamol poisoning as it does not bind NAPQI, the toxic metabolite responsible for liver damage.
**Option B:** Silymarin, a milk thistle extract, has no established efficacy in treating paracetamol poisoning and is not recommended as a treatment.
**Option C:** Penicillin is an antibiotic and has no role in the treatment of paracetamol poisoning.

**Clinical Pearl / High-Yield Fact**
The American Association of Poison Control Centers recommends NAC treatment for patients with paracetamol overdose, even if the time since ingestion is uncertain, as it is generally safe and effective.

**Correct Answer: A. Activated charcoal is not used to treat paracetamol poisoning.