Why does acetylcysteine protect the liver in paracetamol overdose?
Answer and explanation
Correct answer: A. It replenishes glutathione so that the toxic metabolite NAPQI is detoxified
- Step 1: In overdose the safe glucuronidation and sulphation routes saturate, and more paracetamol is oxidised to NAPQI. Step 2. Glutathione normally conjugates NAPQI, but stores are used up. Acetylcysteine supplies cysteine for glutathione synthesis, so NAPQI is neutralised instead of damaging hepatocytes. Answer: It replenishes glutathione so that the toxic metabolite NAPQI is detoxified. Why not the others: Increasing P450 activity would make more NAPQI. Binding in the gut is the role of activated charcoal, not acetylcysteine. Blocking sulphation would push even more drug toward toxic oxidation.
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