Toxicology is one of the most heavily tested domains in the ACEM fellowship written exam. It appears in both MCQ and SAQ components, and questions often require detailed knowledge of specific toxidromes, antidotes, and management algorithms. This guide covers the high-yield themes you should focus on.
Why toxicology matters for the exam
Toxicology questions are common because they test multiple competencies simultaneously: clinical assessment, risk stratification, investigation interpretation, specific management decisions, and disposition planning. A single poisoning scenario can generate questions about pathophysiology, ECG interpretation, decontamination decisions, antidote selection, and monitoring requirements.
Core toxidromes
You must be able to recognise and differentiate the major toxidromes rapidly. While this seems basic, exam questions often present atypical or mixed presentations that require you to distinguish between overlapping toxidromes.
| Toxidrome | Key Features | Common Causes |
|---|---|---|
| Anticholinergic | Tachycardia, mydriasis, dry skin, urinary retention, delirium | Antihistamines, TCAs, atropine |
| Cholinergic | SLUDGE/BBB: salivation, lacrimation, diaphoresis, bradycardia | Organophosphates, carbamates, nerve agents |
| Sympathomimetic | Tachycardia, hypertension, mydriasis, diaphoresis, agitation | Amphetamines, cocaine, synthetic cathinones |
| Opioid | Miosis, respiratory depression, decreased consciousness | Heroin, fentanyl, oxycodone, methadone |
| Serotonin syndrome | Clonus, hyperreflexia, hyperthermia, agitation | SSRIs, MAOIs, tramadol combinations |
High-yield poisonings
Certain poisonings appear repeatedly in the exam because they have specific management pathways, time-critical interventions, or commonly misunderstood pharmacology. Focus your revision on these:
Paracetamol
The most common deliberate self-poisoning in Australasia. You must know the Rumack-Matthew nomogram, indications for N-acetylcysteine, modified-release paracetamol management, and criteria for referral to a liver transplant unit. Staggered overdoses and late presentations are common exam scenarios.
Tricyclic antidepressants
A classic exam topic because of the multi-system toxicity: sodium channel blockade (QRS widening), anticholinergic effects, seizures, and cardiovascular collapse. Know the role of sodium bicarbonate, when to intubate, and the prognostic significance of QRS duration.
Digoxin
Chronic vs acute toxicity presentations differ significantly. Know the indications for digoxin-specific antibody fragments, the associated electrolyte abnormalities (hyperkalaemia in acute toxicity), and the ECG changes.
Beta-blocker and calcium channel blocker overdose
High-dose insulin euglycaemic therapy (HIET) is frequently tested. Know the dosing, mechanism of action, and when to initiate it. Glucagon for beta-blocker overdose, IV calcium for CCB overdose, and the role of lipid emulsion therapy are all common question topics.
Organophosphates
Atropine dosing (titrate to secretions, not heart rate), pralidoxime, and the intermediate syndrome. Australian-context questions may include agricultural exposures.
Decontamination decisions
Know the indications and contraindications for activated charcoal, whole bowel irrigation, and the (very limited) role of gastric lavage. The exam frequently tests whether decontamination is indicated in a specific scenario, and the answer is often that it is not.
Australian toxinology
Envenomation by Australian fauna is a uniquely Australasian exam topic. Key areas include pressure immobilisation bandage technique and indications, snake envenomation syndromes (coagulopathy, myotoxicity, neurotoxicity), box jellyfish and Irukandji management, redback spider bite, and funnel-web spider envenomation. Know the appropriate antivenom for each and the indications for its use.
Practice tip: ACEMCQ has over 170 fellowship-standard toxicology MCQs covering all the topics above, with referenced explanations from Cameron and Tintinalli. Start a free trial to practise them.