Pharmacology. BAL (British anti-lewisite; dimercaprol; 2,3-dimercaptopropanol) is a dithiol chelating agent that is used in the treatment of poisoning by the heavy metals arsenic, mercury, lead, and gold. Because the vicinal thiol groups are unstable in aqueous solution, the drug is supplied as a 10% solution (100 mg/mL) in peanut oil that also contains 20% (200 mg/mL) benzyl benzoate. It is administered by deep IM injection. Most of the drug is absorbed within 1 hour and undergoes widespread distribution to most tissues. BAL, or its in vivo biotransformation product(s), is believed to form complexes with selected toxic metals, thereby minimizing the reaction of the metals with endogenous ligands and increasing their excretion in urine. In a study of humans treated with BAL after exposure to arsenicals, peak urinary arsenic excretion occurred in 2–4 hours and then declined rapidly.

Indications

1. 
   

   Acute inorganic arsenic poisoning. Limited data suggest it may also be useful in the early stages of arsine poisoning (ie, during the first 24 hours).

   
   
2. 
   

   Mercury poisoning (except with monoalkyl mercury). BAL is most effective in preventing renal damage if it is administered within 4 hours after acute ingestion of inorganic mercury salts; its value in averting or treating the acute or chronic neurologic effects of elemental mercury vapor is unknown.

   
   
3. 
   

   Lead poisoning (except with alkyl lead compounds). BAL has been used concomitantly with calcium EDTA (See EDTA, Calcium (Calcium Disodium EDTA, Calcium Disodium Edetate, Calcium Disodium Versenate)) in the treatment of pediatric lead encephalopathy, in which the joint regimen was associated with an accelerated decline in blood lead levels and increased urinary lead excretion. Note: BAL is not for use as a single-drug regimen in lead poisoning.

   
   
4. 
   

   Gold. BAL has been associated with an increase in urinary gold excretion and clinical improvement in patients treated for adverse dermatologic, hematologic, or neurologic complications of pharmaceutical gold preparations.

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