Toxicology & Overdose

Antidotes · Management timelines · TOXBASE protocols

Always contact TOXBASE / NPIS for complex poisonings

NPIS (National Poisons Information Service): 0344 892 0111 (24/7) · TOXBASE online: www.toxbase.org · For life-threatening cases, call 999 and arrange immediate transfer.

Quick Antidote Reference

Paracetamol

N-Acetylcysteine (NAC)

IV

Opioids

Naloxone

IV/IM/IN

Benzodiazepines

Flumazenil (caution)

IV

TCAs

Sodium Bicarbonate

IV

Beta-blockers

Glucagon + HDIE

IV

Ca-channel blockers

Calcium + HDIE

IV

Digoxin

DigiFab

IV

Organophosphates

Atropine + Pralidoxime

IV

Carbon monoxide

100% O₂ / HBO

Inhaled

Iron

Desferrioxamine

IV

Cyanide

Hydroxocobalamin

IV

Methanol/Ethylene glycol

Fomepizole / Ethanol

IV

Paracetamol Overdose

Most common cause of acute liver failure in the UK. Antidote: N-Acetylcysteine (NAC). Time-critical — act within 8 hours for best outcome.

Antidote: NACToxic dose: >150 mg/kg or >7.5 gTOXBASE / NPIS: 0344 892 0111

Clinical Phases

  • Nausea, vomiting, malaise
  • Anorexia, pallor, diaphoresis
  • May appear deceptively well
  • LFTs often normal at this stage

Management Timeline

TimingActionDetail
0–1 hrAssess airway, breathing, circulationGCS, pupils, vital signs. IV access × 2.
0–1 hrActivated charcoal50 g oral if within 1 hour of ingestion and airway protected. Do NOT delay NAC for charcoal.
ASAPParacetamol levelTake at 4 hours post-ingestion (or on arrival if >4 hrs). Plot on Rumack-Matthew nomogram.
ASAPBloodsFBC, U&E, LFT, glucose, PT/INR, VBG/ABG, paracetamol level, salicylate level.
If indicatedStart IV NACIf level above treatment line, staggered overdose, unknown time, or symptomatic. Do NOT wait for level if >8 hrs post-ingestion.
OngoingRepeat LFT, PT, creatinine at 24 hrsIf abnormal, continue NAC and discuss with liver unit.
If severeLiver unit referralApply King's College Criteria. Early listing for transplant if criteria met.

IV N-Acetylcysteine (NAC) Protocol — 21-Hour Regimen

1

Loading dose

150 mg/kg in 200 mL 5% glucose

over 1 hour
2

Second infusion

50 mg/kg in 500 mL 5% glucose

over 4 hours
3

Third infusion

100 mg/kg in 1000 mL 5% glucose

over 16 hours

NAC adverse effects: Anaphylactoid reaction in ~15% (urticaria, bronchospasm) — usually in first infusion. Stop infusion, give chlorphenamine 10 mg IV, restart at slower rate. True anaphylaxis is rare. Do NOT stop NAC permanently unless life-threatening reaction.

King's College Criteria — Liver Transplant Listing

Arterial pH< 7.30 (after resuscitation)
OR all three of:
PT> 100 seconds (INR > 6.5)
Creatinine> 300 µmol/L
EncephalopathyGrade III or IV

Contact nearest liver transplant centre immediately if criteria met. Sensitivity ~70%, specificity ~90% for death without transplant.

TOXBASE; MHRA 2012 Guidance; NICE CG152; King's College Hospital Criteria; NPIS 0344 892 0111