Acetylcysteine (N-acetylcysteine — Paracetamol Overdose)

How it works

It replenishes hepatic glutathione and provides sulfhydryl groups that detoxify the reactive paracetamol metabolite (NAPQI), protecting hepatocytes from injury.

Prescribing in practice

• Anaphylactoid reactions (flushing, urticaria, itch and bronchospasm) are common and are usually infusion-rate related — slow or pause the infusion and treat the reaction, then resume.
• It is most effective started early but is given later where the treatment protocol indicates, including in late presentation, staggered overdose or established liver injury.
• Treatment decisions follow the paracetamol treatment nomogram and timing, with Toxbase/NPIS advice for staggered or uncertain-timing ingestions.

Monitoring

Monitor for anaphylactoid reactions during the infusion, and track paracetamol level (where timing allows), liver function, INR, renal function and acid-base status to guide continuation and assess hepatotoxicity.

Counselling the patient

• Brief the team that infusion-related reactions are common, manageable by slowing or pausing the infusion, and not a true allergy that contraindicates the antidote.
• Reassure the patient that the reaction can be controlled and treatment continued.
• Follow the treatment nomogram and Toxbase/NPIS advice for ongoing management.

Evidence & guidelines

Established antidote for paracetamol poisoning (Toxbase/NPIS).