Key Facts

Poisoning accounts for over 170,000 hospital presentations per year in England. It is the leading cause of death in young adults (15-35 years) and is frequently associated with mental health conditions and substance misuse.

Epidemiology

• >100,000 ED attendances for self-poisoning per year in England
• Paracetamol is involved in ~50% of poisoning presentations
• ~5,000 deaths from poisoning per year in the UK (including drug misuse deaths)
• Self-poisoning accounts for ~80% of self-harm hospital presentations

Aetiology

• Intentional self-harm: ~80% of poisoning presentations (impulsive in many)
• Accidental ingestion: Especially in children under 5 years
• Recreational drug use: MDMA, cocaine, novel psychoactive substances
• Iatrogenic: Medication errors, drug interactions

Pathophysiology

Mechanisms of toxicity depend on the agent:

• Paracetamol: NAPQI (toxic metabolite) depletes glutathione → hepatocyte necrosis
• Opioids: Mu-receptor agonism → respiratory depression
• Tricyclics: Sodium channel blockade (broad QRS), anticholinergic effects, alpha-blockade
• Salicylates: Uncoupling of oxidative phosphorylation, direct CNS stimulation
• Organophosphates: Irreversible acetylcholinesterase inhibition

Toxidromes

• Sympathomimetic (cocaine, amphetamines): Tachycardia, hypertension, hyperthermia, mydriasis, agitation
• Anticholinergic (TCAs, antihistamines): 'Hot as a hare, blind as a bat, dry as a bone, red as a beet, mad as a hatter'
• Cholinergic (organophosphates): SLUDGE — Salivation, Lacrimation, Urination, Defaecation, GI distress, Emesis
• Opioid: Pinpoint pupils, respiratory depression, reduced consciousness
• Serotonin syndrome: Clonus, agitation, hyperthermia, hyperreflexia

Red Flags

• Altered consciousness (GCS <8 — protect airway)
• Respiratory rate <12 or >25
• Seizures
• Cardiac arrhythmias (prolonged QRS >120ms or QTc >500ms)
• Metabolic acidosis (pH <7.30)
• Liver failure features (coagulopathy, encephalopathy) in paracetamol overdose

Bedside

• A-E assessment: ABCDE approach, ensure airway protection
• ECG: QRS duration (TCA), QTc (many drugs), ST changes
• Blood glucose: Hypoglycaemia (insulin, sulfonylureas, alcohol)
• Temperature: Hyperthermia (serotonin syndrome, NMS, sympathomimetics)

Bloods

• Paracetamol level: At 4 hours post-ingestion (or ASAP if staggered)
• Salicylate level: If suspected
• ABG/VBG: Acid-base status, lactate, carboxyhaemoglobin
• U&Es: Renal function, potassium
• LFTs and INR: Hepatotoxicity assessment
• FBC, glucose, CRP: Baseline

Imaging

• CXR: Aspiration pneumonitis, pulmonary oedema
• CT head: If reduced consciousness and diagnosis uncertain, or suspected head injury

Special Tests

• Urine drug screen: Cocaine, opioids, benzodiazepines, amphetamines
• TOXBASE consultation: For specific agent guidance
• Carboxyhaemoglobin: CO poisoning (take sample before O2 therapy if possible)

Non-pharmacological

• Airway protection: Intubation if GCS <8
• Activated charcoal: 50g PO within 1 hour of ingestion (most toxins)
• Whole bowel irrigation: Sustained-release preparations, body packers

Pharmacological

Specific antidotes:

• Paracetamol → N-acetylcysteine (NAC): 150mg/kg in 200mL 5% dextrose over 1h, then 50mg/kg over 4h, then 100mg/kg over 16h
• Opioids → Naloxone: 400mcg IV, repeat every 2-3 min (max 10mg); consider infusion (short half-life)
• Benzodiazepines → Flumazenil: 200mcg IV, then 100mcg every 60s (max 2mg) — caution in chronic use/mixed OD
• TCAs → Sodium bicarbonate 8.4%: 50mL IV if QRS >120ms or arrhythmias
• Beta-blockers → Glucagon: 2-10mg IV bolus, then infusion
• Organophosphates → Atropine (high dose) + pralidoxime
• Digoxin → DigiFab: Digoxin-specific antibody fragments
• Iron → Desferrioxamine: 15mg/kg/h IV
• Methanol/ethylene glycol → Fomepizole (or ethanol infusion) + haemodialysis

Surgical/Interventional

• Haemodialysis: Lithium, salicylates, methanol, ethylene glycol, theophylline
• Intralipid (lipid emulsion): Local anaesthetic toxicity, lipophilic drug overdose

Referral Criteria

• All intentional self-harm → psychiatric assessment before discharge
• Severe poisoning → ICU/toxicology
• Paracetamol with high-risk features → liver unit (King's College criteria)
• National Poisons Information Service (NPIS): 0344 892 0111

• Paracetamol overdose: Mortality <1% if NAC given within 8 hours; ~5% mortality with established liver failure
• Opioid overdose: Excellent prognosis with timely naloxone administration
• TCA overdose: Mortality 2-5% in severe cases; most deaths from arrhythmias
• Overall poisoning mortality in hospital: <1% with appropriate management
• Risk of repeat self-harm within 1 year: ~25%; suicide risk ~3% over 5 years

Key Antidotes Summary

King's College Criteria for Liver Transplant (Paracetamol)