dimercaprol

Dimercaprol, also known as British anti-Lewisite (BAL), is a chelating agent used in the treatment of certain heavy metal poisonings. It is a dithiol compound named 2,3-dimercapto-1-propanol and is usually administered intramuscularly. BAL has historically been prepared in an oil vehicle, such as peanut or sesame oil, which is a consideration for individuals with peanut or sesame allergies.

Mechanism and pharmacology

Dimercaprol works by binding metal ions through its two sulfhydryl (thiol) groups, forming stable metal–BAL chelates that are more readily excreted by the kidneys. The resulting complexes reduce the bioavailability of toxic metals and help mobilize metals from tissues into the bloodstream for elimination. BAL is particularly noted for chelating arsenic, inorganic mercury, lead, and gold; it is less effective for methylmercury poisoning and is not generally considered first-line for all heavy metal intoxications.

Medical uses and limitations

BAL has been used for acute arsenic and inorganic mercury poisoning, lead poisoning, and certain gold salt poisonings. In modern practice, it is often part of a broader, staged chelation strategy and may be combined with other chelators. However, its use has declined in some settings due to adverse effects and the availability of newer agents. BAL is not universally effective for all metal species and situations; its benefit must be weighed against potential risks.

Safety and contraindications

Adverse effects include hypertension, tachycardia, fever, nausea, vomiting, abdominal pain, injection-site reactions, and nephrotoxicity. Allergies to the oil vehicle (peanut or sesame) can be contraindications. BAL can cause hypersensitivity reactions and is generally avoided in pregnant individuals unless the potential benefit outweighs risk. Careful monitoring of renal function, electrolytes, and vital signs is standard during therapy.

History

Developed in the 1940s as an antidote to lewisite, BAL earned the name British anti-Lewisite. Although largely supplanted by newer chelators in many indications, BAL remains a historical and, in some settings, a clinically relevant option for certain severe metal poisonings.