What is the antidote for Paracetamol (PCM) overdose?

N-acetylcysteine is the antidote for paracetamol (PCM) overdose and works by replenishing glutathione levels in the liver, which is crucial for detoxifying the toxic metabolite of paracetamol, N-acetyl-p-benzoquinone imine (NAPQI). In cases of overdose, the liver's stores of glutathione become depleted, and N-acetylcysteine acts to replete these stores, thus preventing or mitigating liver damage. It is most effective when administered within 8 to 10 hours of the overdose but can still provide benefit even if given later.

The other substances listed do not counteract paracetamol overdose. Flumazenil is an antidote for benzodiazepine overdose and does not have a role in treating PCM toxicity. Digoxin immune Fab is used for digoxin toxicity, specifically to bind and neutralize digoxin when present in the body. Glucagon is employed in cases of beta-blocker or calcium channel blocker overdose but is not indicated for paracetamol overdose. Therefore, N-acetylcysteine is the only appropriate and effective choice in this scenario.