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Antidotes & Toxicology Pregnancy: Use only if life-threatening — limited human data; animal studies show foetal abnormalities; consult NPIS

Dimercaprol

Brand names: BAL — British Anti-Lewisite

Adult dose

Dose: 2.5–3 mg/kg every 4 hours for 2 days, then 2.5 mg/kg twice daily for 1 day, then 2.5 mg/kg once daily for 10 days or until recovery
Route: IM deep
Frequency: Variable — see schedule
Max: 3 mg/kg per dose
Formulated in peanut oil — CONTRAINDICATED in peanut allergy. Must give IM, NOT IV. For severe arsenic: 3 mg/kg every 4 hours for 2 days

Paediatric dose

Dose: 2.5–3 mg/kg mg/kg
Route: IM
Frequency: Every 4 hours initially
Max: 3 mg/kg per dose
Same schedule as adult; IM injection painful — seek specialist paediatric toxicology opinion

Dose adjustments

Renal

Use with extreme caution in renal impairment — dimercaprol-metal complexes are nephrotoxic; ensure adequate urine output; may need haemodialysis

Hepatic

Contraindicated in hepatic impairment (except arsenic-induced hepatotoxicity)

Paediatric weight-based calculator

Same schedule as adult; IM injection painful — seek specialist paediatric toxicology opinion

Clinical pearls

  • Indications: acute arsenic, inorganic mercury, and lead poisoning (especially when used with DMSA/succimer or EDTA); historically first-line for Lewisite chemical warfare agent exposure
  • Mechanism: dithiol structure forms stable water-soluble chelate complexes with heavy metals, which are then excreted in urine and bile
  • PEANUT OIL VEHICLE: ALWAYS screen for peanut allergy before administering — this is a critical MHRA safety point for every administration
  • NEVER use for iron, cadmium, or selenium toxicity — the dimercaprol complexes are more nephrotoxic than the metals themselves; EDTA or deferasirox preferred for iron overload
  • Lead poisoning: dimercaprol used in combination with calcium EDTA for severe lead encephalopathy in children (blood lead above 70 mcg/dL); succimer (DMSA) preferred for less severe cases
  • Arsenic poisoning: dimercaprol 3 mg/kg every 4 hours for 2 days is standard; NPIS should always be contacted (0344 892 0111)

Contraindications

  • Peanut allergy — formulation contains peanut oil — ABSOLUTE contraindication
  • Hepatic impairment (except arsenic-induced liver damage)
  • Iron, cadmium, or selenium poisoning — dimercaprol-iron and dimercaprol-cadmium complexes are MORE toxic than the metals themselves
  • Concurrent penicillamine therapy

Side effects

  • Pain at IM injection site
  • Hypertension and tachycardia (dose-dependent)
  • Nausea and vomiting
  • Headache
  • Burning sensation of lips, mouth, throat
  • Lacrimation, rhinorrhoea
  • Nephrotoxicity
  • Children may experience fever during treatment

Interactions

  • Iron supplements — do NOT give oral iron within 24 hours — toxic dimercaprol-iron complex
  • Penicillamine (additive toxicity — do not use together)
  • Mercury (dialkylamercury compounds — dimercaprol may NOT be effective)

Monitoring

  • Urine output and renal function (nephrotoxicity)
  • Blood pressure and heart rate
  • Urine pH — alkalinise to prevent renal precipitation of dimercaprol-metal complexes
  • Urinary heavy metal excretion (24-hour collection)
  • Blood or urine arsenic, lead, or mercury levels

Reference: BNFc; BNF 90; NPIS Toxbase; WHO Model Formulary; Clinical Toxicology 2004;42(4):347-357. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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