Poisoning approach and drug overdoses

Initial approach and toxidromes

Reviewed Nov 2026·3 references
New· views rounded down, updated weekly

Resuscitate first, recognise the toxidrome, run the standard poisoning screen, and use the poisons information centre.

Definition
Most poisoned patients survive with good supportive care. The priority is airway, breathing, circulation, glucose and seizure control, then a focused toxicological assessment.

At the bedside

Timed steps
  1. 1

    ABCDE with glucose

    0 min

    Airway (aspiration risk with GCS ≤ 8 - but avoid reflex intubation in opioid toxicity if naloxone works), oxygen, IV access, capillary glucose, temperature.

  2. 2

    History from all sources

    What, how much (mg/kg), when, route, co-ingestants (alcohol), intent, pill bottles, family members, prescriptions; ask about household pesticides and plants.

  3. 3

    Examine for a toxidrome

    Pupils, skin (sweat/dry), temperature, HR, BP, RR, bowel sounds, mental status, clonus/rigidity.

  4. 4

    Standard investigations

    12-lead ECG (QRS, QTc, R in aVR), VBG/ABG with lactate, electrolytes, creatinine, LFT, paracetamol (all intentional overdoses) and salicylate levels, serum osmolality (osmolal gap), CK, pregnancy test.

  5. 5

    Specific measures

    Decontamination if indicated, antidote if available, enhanced elimination if criteria met (see topics).

  6. 6

    Seizures and agitation

    Benzodiazepines first line (lorazepam 4 mg or midazolam 10 mg IM); avoid phenytoin in toxic seizures.

  7. 7

    Psychiatric assessment

    All deliberate self-harm needs psychiatric evaluation before discharge; document capacity.

Opioid toxicity

Naloxone

IV/IM
Dose
0.04-0.4 mg, repeat every 2-3 min to RR > 10
Worked example
Apnoeic: 0.4 mg IV; partial response: 0.1 mg aliquots; infusion 2/3 of total effective dose per hour

Toxidromes

ToxidromeFeaturesExamples
AnticholinergicHot, dry, flushed, mydriasis, delirium, urinary retention, tachycardia, reduced bowel soundsTCA, antihistamines, datura (common in India), atropine
CholinergicSLUDGE/DUMBELS, miosis, bradycardia, bronchorrhoea, fasciculations, weaknessOrganophosphates, carbamates (see agrochemical module)
SympathomimeticAgitation, mydriasis, sweating, tachycardia, hypertension, hyperthermiaAmphetamines, cocaine, caffeine, theophylline
OpioidComa, miosis, respiratory depressionMorphine, tramadol, heroin, codeine syrups
Sedative-hypnoticComa with relatively normal vital signsBenzodiazepines, barbiturates, zolpidem
Serotonin syndromeClonus (inducible/ocular), hyperreflexia, agitation, sweating, hyperthermiaSSRIs, tramadol, linezolid, methylene blue combinations
Red flag · call your senior now
QRS > 100 ms, seizures, hyperthermia > 40 °C, or refractory hypotension: high-risk poisoning - ICU and toxicology advice.
Pitfall
Missing paracetamol co-ingestion: check levels in all intentional overdoses.
Pitfall
Attributing coma to alcohol without checking glucose, head CT and other toxins.
Pearl
Serotonin syndrome develops over hours with clonus; neuroleptic malignant syndrome develops over days with lead-pipe rigidity.

Calculators for this topic

Glasgow Coma Scale

Eye + Verbal + Motor (3-15). Record components, e.g. E3 V4 M5.

Osmolal gap

Measured − calculated osmolality. Raised in toxic alcohol poisoning.

Corrected QT (Bazett)

QT ÷ √(RR in seconds). Over-corrects at fast heart rates.

References

  1. 1

    Farkas J. The Internet Book of Critical Care (IBCC). EMCrit Project; continuously updated.

  2. 2

    Chiew AL, Reith D, Pomerleau A, et al. Updated guidelines for the management of paracetamol poisoning in Australia and New Zealand. Med J Aust 2020;212:175-83.

  3. 3

    Chyka PA, Seger D, Krenzelok EP, Vale JA; AACT/EAPCCT. Position paper: single-dose activated charcoal. Clin Toxicol 2005;43:61-87.

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Decontamination and enhanced elimination

Educational reference for trained clinicians. Check doses against your hospital protocol and the patient in front of you.