Dimercaprol

This rarely used intramuscular chelator is the most toxic of all chelating agents, and is reserved for the treatment of severe poisoning from lead, inorganic arsenic and mercury, if possible EDTA or Succimer should be used instead.

Administration:

• Always in ICU due to the severity of the underlying condition and adverse effects.
• Alkalinise the urine prior to administration to reduce the risk of nephrotoxicity.

Severe inorganic arsenic or mercury poisoning:

• Give 3 mg/kg IM every 4 hours for 48 hours then…..
• Give 3 mg/kg IM every 12 hours for 7 – 10 days depending on the clinical response

Lead encephalopathy:

• Commence dimercaprol 4 hours before commencing EDTA
• Give 4 mg/kg every 4 hours for 5 days

Side effects:

• Pain and sterile abscess formation
• Fever and myalgia
• Chest pain, hypertension (can induce a hypertensive encephalopathy) and tachycardia
• Peripheral paraesthesia
• Lacrimation
• Risk of intravascular haemolysis in patients with G6PD deficiency
• Nephrotoxicity (dimercaprol-metal complexes in acidic urine)

References

• Gold H. BAL (British anti-lewisite).  American Journal of Medicine 1948; 4: 1-2
• Vilensky JA, Redman K. British Anti-Lewisite (Dimercaprol): An amazing history. Annals of Emergency Medicine 2003; 41:378-383.