Poisoning, toxidromes and antidote decisions

Stabilise and identify the exposure

Assess airway, breathing, circulation, glucose, temperature and mental state before pursuing a detailed toxicology history. Call the Australian Poisons Information Centre on 13 11 26 for exposure-specific advice and involve a clinical toxicologist for serious cases. Ask the product, formulation, maximum possible amount, time, route, co-ingestants and relevant comorbidities. Obtain packaging where safely available. The patient's estimate may be incomplete, particularly after deliberate self-poisoning. Modified-release preparations and long-acting substances can produce delayed toxicity despite an initially normal examination.

Use ECG and directed blood tests according to the possible poison. QRS widening, QT prolongation, bradycardia or arrhythmia can identify urgent cardiotoxicity. A routine urine drug screen has limited coverage and can be falsely positive or remain positive after intoxication resolves. It must not overrule the clinical syndrome. Protect staff and the patient from secondary exposure after chemical contamination. Skin/eye irrigation and decontamination may be immediate priorities; avoid transferring contaminated clothing into an unprepared clinical area.

Recognise toxidromes

Opioid toxicity causes reduced ventilation and consciousness, often with small pupils. Support ventilation and give titrated naloxone when indicated; awakening is not the sole endpoint. Long-acting exposure may require an infusion and prolonged monitoring because naloxone wears off earlier. Sedative co-ingestion may leave persistent impairment. Sympathomimetic toxicity can produce agitation, sweating, hypertension and hyperthermia; benzodiazepines, cooling and complication assessment are central. Anticholinergic toxicity can look similar but often has dry skin/mouth and urinary retention; specific antidote use needs toxicology advice.

Cholinergic poisoning can cause secretions, bronchospasm, diarrhoea, small pupils and weakness. Protect staff and use the organophosphate-specific pathway where relevant. Serotonin toxicity often features clonus and hyperreflexia after relevant medicines, while NMS commonly causes rigidity with dopamine-blocking exposure. These are clinical patterns, not diagnoses established by one temperature reading. Treat hyperthermia actively, stop triggers and seek specialist care. A delirious agitated patient may also have infection, hypoglycaemia or head injury, which must not be missed because a substance history is present.

Paracetamol and common medicines

Paracetamol poisoning can initially be asymptomatic. Assess it in deliberate adolescent/adult self-poisoning and consider combination products. For a single immediate-release ingestion at a known time, a concentration at or after four hours is interpreted with the treatment nomogram and the current Australian pathway. An earlier low level cannot safely exclude toxicity. Unknown time, repeated supratherapeutic dosing and modified-release exposure require different algorithms and often repeat levels. Acetylcysteine is time-sensitive; do not delay indicated treatment while awaiting a result that will arrive late.

Monitor liver tests, INR, kidney function and concentrations as specified, and use protocol criteria for stopping or extending acetylcysteine. A completed standard infusion does not automatically prove treatment can stop. Tricyclic poisoning can cause seizures, hypotension and QRS widening, needing sodium bicarbonate and monitored specialist care when indicated. Salicylate poisoning can cause tinnitus, vomiting, tachypnoea and mixed acid–base disturbance; levels and clinical status may warrant alkalinisation or dialysis. Avoid assuming a normal pH means there is no serious acid–base problem.

Decontamination and special exposures

Activated charcoal is used only for selected substances and time frames with a safe airway and toxicology advice. It is not routine for every ingestion and is unsuitable for some exposures. Do not induce vomiting or use gastric lavage as a universal first step. Caustic ingestion requires airway/GI assessment and advice; avoid neutralisation attempts that create heat or further injury. Hydrocarbon aspiration risk can dominate management even when the swallowed volume is small. A battery or magnet ingestion follows a foreign-body pathway rather than a standard medicine-overdose algorithm.

Carbon monoxide can produce headache, nausea, confusion and collapse, sometimes affecting several people in one environment. Standard pulse oximetry can be misleading; assess exposure and co-oximetry where appropriate, give indicated oxygen and obtain expert advice. Cyanide risk may coexist in severe enclosed-space fires. Toxic alcohols can cause delayed metabolic acidosis and organ injury; antidote and dialysis decisions are time-sensitive. Do not wait for every specialised assay before seeking advice when the clinical/exposure pattern is concerning.

Disposition and self-harm care

Observation duration follows the substance, formulation, clinical course and treatment, not one universal six-hour rule. Consider delayed cardiac, respiratory and hepatic effects. Deliberate self-poisoning needs a psychosocial assessment and an individual safety plan after stabilisation, with assessment of current intent, supports and access to means. A statement of regret does not replace that assessment. Check safeguarding for children and vulnerable adults, including accidental dosing errors and access to medicines at home.

For example, an apparently well patient presents two hours after a potentially large paracetamol ingestion. Arrange the correctly timed concentration and guideline-based treatment assessment; do not discharge from an early low level. A drowsy patient after methadone may re-sedate after naloxone and needs prolonged monitored care. Record exposure uncertainties, advice received, treatment endpoints and handover responsibilities so the next clinician knows what still needs checking.

RCH paracetamol poisoning.

Review checkpoints

• Contact the Australian Poisons Information Centre on 13 11 26 for specific advice.
• An early paracetamol concentration cannot exclude toxicity before the appropriate sampling time.
• Activated charcoal is selective treatment and requires attention to airway safety.