Overdose and Poisoning Treatment

NICE BNF Treatment summaries. Poisoning, emergency treatment.

Article Last Updated:21/11/2025

Minor changes were made to the active elimination techniques section, and the management of tricyclic antidepressant toxicity was added.

Date: 21/11/25

Guidelines

Active Elimination Techniques

Activated Charcoal

Consider oral activated charcoal if patient presents within 1 hour of ingestion of a poison / drug that is absorbed in the gut and binds well to charcoal

Activated charcoal can be used in most oral drug overdoses, with notable exceptions listed below
Common drug overdose examples that activated charcoal can be used: paracetamol, aspirin, psych drugs (antidepressants, antipsychotics, benzodiazepines), cardiac drugs (beta blocker, calcium channel blocker), antiepileptics, theophylline

Activated charcoal should NOT be used for the following poisonings:

Alcohols (e.g. ethanol, polyethylene glycol, methanol)
Metal salts (e.g. lithium, iron, mercury, lead)
Cyanides
Hydrocarbons (e.g. petrol, kerosene)
Corrosive substances (acids and alkalis like bleach and drain cleaner)
Malathion

Haemodialysis

Haemodialysis is only suitable for severe toxicity from the following drugs:

Ethylene glycol
Lithium
Methanol
Phenobarbital
Salicylates (e.g. aspirin)
Sodium valproate

Gastric Lavage

Gastric lavage has limited use, it is typically reserved for iron and lithium overdose, if presented within 1 hour of ingestion

To perform gastric lavage, the patient must be intubated with an endotracheal tube for airway protection (due to risk of aspiration).

In exam questions on overdose, gastric lavage is almost always the incorrect answer… just included as an distractor.

There is lack of guidelines and consensus statements regarding use of gastric lavage, it is also rarely performed in clinical practice.

Recognition and Management

This section outlines the antidote of various high-yield / common poisoning.

Drug / substance	Features	Treatment
Aspirin	Hyperventilation Tinnitus Deafness Sweating Flushing, dizziness (from vasodilatation) Mixed respiratory alkalosis (early) and metabolic acidosis (late)	1st line: IV sodium bicarbonate (urinary alkalinisation to promote renal elimination) Ensure to correct hypokalaemia before giving sodium bicarbonate Severe poisoning: haemodialysis
Opioids (e.g. morphine, oxycodone, fentanyl)	Classic triad of: Respiratory depression Bilateral miosis Reduced level of consciousness	1st line: naloxone (rapid 400 mcg IV bolus, repeat at 1 min intervals) If no IV access: IM injection is an alternative option If there is no response to naloxone, consider benzodiazepine poisoning, as both can present similarly.
Paracetamol	Early features: nausea and vomiting (usually settle within 24 hours) Liver damage is indicated by: RUQ pain and tenderness (maximal 3-4 days after the overdose)	N-acetylcysteine (see the paracetamol article for guidance on when to use N-acetylcysteine)
SSRIs (e.g. sertraline, fluoxetine)	Nausea and vomiting Agitation Tremor Nystagmus Drowsiness Sinus tachycardia Convulsions	Supportive management: Consider oral activated charcoal (if within 1 hour of ingestion) Treat convulsions with benzodiazepines
TCAs (e.g. amitriptyline)	Sodium channel blockage (QRS prolongation, ventricular arrhythmias, seizures) Anti-muscarinic effect (mydriasis, dry mouth, urinary retention, warm flushed skin) Anti-histaminergic effect (sedation, drowsiness, coma)	There is no specific antidote for TCA toxicity: Supportive measures to ensure a clean airway and adequate ventilation IV sodium bicarbonate if QRS is widened (>100 ms) (avoid antiarrhythmics ) IV lorazepam / diazepam to treat convulsions
Benzodiazepine	Drowsiness Ataxia Dysarthria Nystagmus Respiratory depression (not always)	Consider flumazenil only under specialist advice Can be hazardous, esp. in mixed overdoses involving TCAs or in benzodiazepine-dependent patients May inhibit respiration (esp. in those with severe respiratory disorders)
Beta blocker	Cardiac features (primary): Bradycardia – most common Hypotension Syncope Conduction abnormalities Heart failure Other features: Respiratory depression, bronchospasm CNS effects – drowsiness, confusion, convulsions, hallucinations)	Fluid resuscitation Symptomatic bradycardia → atropine Severe hypotension / heart failure / cardiogenic shock → consider IV glucagon
Calcium channel blocker	Nausea and vomiting Dizziness Agitation Confusion	Consider: Calcium chloride or gluconate Treat symptomatic bradycardia with atropine
Iron salts	Nausea and vomiting Abdominal pain Diarrhoea Haematemesis Rectal bleeding	Desferrioxamine
Lithium	Coarse tremor Polydipsia and polyuria (from nephrogenic DI) Ataxia Dysarthira Confusion Seizure (in severe toxicity)	Supportive treatment: fluid resuscitation to correct dehydration and electrolyte balance If serum lithium concentration >2 mmol/L + neurological symptoms or renal failure → haemodialysis
Cocaine	Cocaine is a CNS stimulant Agitation Mydriasis Tachycardia, hypertension Hallucinations Hyperthermia Classic cocaine clues: Chest pain Nasal septum perforation	Diazepam to control agitation Cooling measures to manage hyperthermia
Ecstasy	Ectasy is a CNS stimulant Agitation Mydriasis Tachycardia, hypertension Hallucinations Classic MDMA clues: Hyponatraemia (from SIADH) Severe hyperthermia	Diazepam to control agitation
Ethylene glycol (e.g. antifreeze) and methanol	Ethylene glycol → oxalate crystals and kidney failure (late) Methanol → visual disturbances and blindness (late)	1st line: fomepizole 2nd line: ethanol (IV or by mouth)
Carbon monoxide	Headache – most early feature Nausea Dizziness Cherry-red skin Normal SpO₂ + ↑ carboxyhaemoglobin	100% high-flow oxygen (aim SpO₂: 100%)
Methaemoglobinaemia	Chocolate-coloured blood (instead of bright red) Cyanosis that does NOT improve with oxygen ↓ SpO₂ + normal PaO₂	Methylene blue (methylthioninium chloride)
Organophosphate insecticides	Organophosphate inhibits acetylcholinesterase → cholinergic overstimulation Diarrhoea Urination Miosis Lacrimation Sweating Salivation Bradycardia, bronchospasm	1st line: atropine Adjunct: pralidoxime chloride

References

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