A 25-year-old female presents to the emergency department after taking 30 tablets of paracetamol l. They took the first tablet 6 hours ago and took the rest over the course of 5 hours. They feel very nauseous and have vomited, but are otherwise well. Their past medical history includes anorexia nervosa and borderline personality disorder.

Which of the following is the best next step in the management of this patient?

Options:
explanation: This patient is presenting with a paracetamol overdose. However, they took the first dose 6 hours ago. Activated charcoal binds to paracetamol in the GI tract, preventing its absorption. As this patient is not presenting within 1 hour of their overdose, the paracetamol has already absorbed, so activated charcoal will not be effective
name: Give activated charcoal
label: b
answer: no
explanation: IV sodium bicarbonate can be used to manage salicylic (aspirin) overdose and tricyclic antidepressant overdose. It does not play a role in the management of paracetamol overdose
name: Start IV sodium bicarbonate
label: e
answer: no
explanation: Paracetamol overdose can be life-threatening and associated with hepatocellular necrosis, renal tubular necrosis, hepatic encephalopathy and death. The most common symptoms of paracetamol overdose are nausea and vomiting. Some patients may also be asymptomatic. The toxic dose of paracetamol is generally >150mg/kg, which this patient would be above, presuming they are 60-100kg. The management of paracetamol overdose depends on certain clinical factors:

- Give immediate n-acetylcysteine — if ingested >15 hours ago or a staggered overdose (taking above recommended dose of paracetamol spaced over more than 1 hour)
- Give activated charcoal — if ingested within the last hour
- Wait until 4 hours after ingestion to take paracetamol level — if presenting with ingestion less than 4 hours ago
- Take a paracetamol level — if presenting 4 hours after ingestion

When taking a paracetamol level before treatment, use a nomogram to determine whether nN-acetylcysteine should be given, based on the plasma concentration of paracetamol at that time. N-acetylcysteine also should be given immediately to those at increased risk of toxicity, including those on enzyme inducers, those with pre-existing liver disease or regular alcohol use and those with glutathione depletion (e.g. eating disorders, malnutrition).

This patient has presented with a staggered overdose of paracetamol, and they have a history of anorexia nervosa that may put them in a glutathione depleted state. These are both indications to start immediate N-acetylcysteine, so this should be the next step in managing this patient
name: Start N-acetylcysteine
label: a
answer: yes
explanation: As this overdose has been staggered, a plasma paracetamol concentration will not be accurate enough to guide management. It is, therefore, more appropriate to commence treatment with N-acetylcysteine without a paracetamol level
name: Take immediate paracetamol level
label: d
answer: no
explanation: This patient is presenting with a paracetamol overdose. However, this a staggered overdose. As the overdose has been taken over a considerable period, a plasma paracetamol concentration will not be accurate enough to guide management. It is, therefore, more appropriate to commence treatment with N-acetylcysteine without a paracetamol level
name: Wait 4 hours to take a paracetamol level
label: c
answer: no

Correct answer: a