Toxicology and First Aid for Poisoning
Core concepts
Candidates must understand the general management of poisoning: stabilisation (airway, breathing, circulation), decontamination (activated charcoal within about 1 hour of ingestion, gastric lavage only in selected cases), and the use of antidotes. Know the classic toxidromes: opioid (pinpoint pupils, respiratory depression, coma → naloxone), anticholinergic (dry skin, flushing, mydriasis, delirium → supportive; physostigmine in selected cases), cholinergic/organophosphate (SLUDGE, bradycardia → atropine plus pralidoxime), sympathomimetic (tachycardia, hypertension, agitation), and sedative-hypnotic. Know specific antidotes: paracetamol → N-acetylcysteine; warfarin → vitamin K; benzodiazepines → flumazenil (caution); iron → desferrioxamine; methanol/ethylene glycol → fomepizole or ethanol; cyanide → hydroxocobalamin. Understand the role of the poison centre and the importance of history, timing, and serial observation.
Traps
Examiners test the timing of activated charcoal (not after the window), the danger of inducing vomiting (never in caustic ingestion or impaired consciousness), and the caution with flumazenil in mixed overdose or benzodiazepine-dependent patients (seizure risk). Another trap is confusing the antidote for organophosphate poisoning: atropine controls muscarinic effects, pralidoxime reactivates the enzyme - both may be needed.
Rule of thumb
For any poisoning scenario, apply: stabilise → identify the toxidrome → give the specific antidote if one exists → support and monitor. Never induce vomiting; use activated charcoal early and only when the airway is protected.
Worked example
A patient presents 4 hours after a paracetamol overdose. Activated charcoal is no longer useful, but N-acetylcysteine should be given based on the timed serum paracetamol level plotted on the treatment nomogram, with liver function monitored.