Paracetamol poisoning — formative SAQs

1. Nomogram decision and activated charcoal

This is a single acute ingestion with a known time, so the four-hour level can be plotted on the Rumack-Matthew nomogram. A level of 180 milligrams per litre at four hours is above the 150 milligrams per litre treatment line, so intravenous N-acetylcysteine is indicated. Because the child presents within one hour of ingestion and has taken a significant dose, activated charcoal is indicated: 1 gram per kilogram by mouth, that is 20 grams (maximum 50 grams), given now before absorption completes, weighing the benefit against the ongoing vomiting and airway risk. ^[1]

2. The intravenous N-acetylcysteine regimen

The standard intravenous regimen is 150 milligrams per kilogram over one hour, then 50 milligrams per kilogram over four hours, then 100 milligrams per kilogram over sixteen hours, a total of 300 milligrams per kilogram over twenty-one hours. For this twenty-kilogram child that is a 3-gram loading dose, then 1 gram, then 2 grams, given in glucose-containing fluid per the local protocol. I confirm the exact regimen with the poisons information centre because it is region-specific. ^{[1] [9]}

3. An anaphylactoid reaction to NAC

This is an anaphylactoid (non-IgE) reaction to the loading dose of N-acetylcysteine, driven by the high peak concentration: flushing, rash, itch and mild bronchospasm are typical. I slow or briefly pause the infusion and give an antihistamine, then resume the regimen once the reaction settles. It is not a reason to abandon the antidote. If bronchospasm or hypotension is severe I treat along the standard anaphylaxis pathway, but most reactions are rate-related and settle with slowing. ^[9]

4. Stopping and extending the course

I stop the standard course if the ALT and INR are normal or falling, the paracetamol level is negligible, the child is clinically well, and there is no co-ingestant or safeguarding concern. If the ALT and INR are rising at twenty-one hours, the child has ongoing hepatotoxicity, so I extend the N-acetylcysteine (commonly continuing the third-bag rate) until the liver is recovering, monitor the prothrombin time trend closely, and escalate to the liver transplant centre if King's College criteria appear. ^{[1] [10]}