British Anti-Lewisite, commonly known as dimercaprol, is a medication used to treat heavy metal poisoning. It functions as a chelating agent, binding to certain metal ions in the body. Its development marked a significant advancement in toxicology, providing a countermeasure against previously untreatable substances. Dimercaprol remains relevant in medicine due to its effectiveness in specific poisoning scenarios.
Origins and Purpose
Dimercaprol’s origins lie in the urgent need for defense against chemical warfare agents during World War II. British scientists developed this compound, originally named British Anti-Lewisite (BAL), as an antidote to Lewisite. Lewisite was an arsenic-based blistering agent, a potent chemical weapon that threatened soldiers. Its development in 1940 by an Oxford University group aimed to mitigate severe tissue damage caused by Lewisite’s interaction with protein sulfhydryl groups.
The full chemical name for BAL is 2,3-dimercaptopropan-1-ol. DuPont produced it during World War II. Although Lewisite was not widely used in combat, research into its antidote led to a revolutionary treatment for heavy metal poisonings, extending beyond its initial military purpose.
How It Counteracts Poisons
Dimercaprol functions as a chelating agent. Its mechanism relies on its two sulfhydryl (thiol) groups, which have a strong affinity for heavy metal ions like arsenic, mercury, gold, and lead. When introduced into the body, these groups bind to toxic metal ions.
This binding forms a stable, five-membered ring structure, neutralizing the metal’s toxicity. The resulting dimercaprol-metal complex is water-soluble, allowing the body to excrete it more easily, primarily through the kidneys. This process reduces free, toxic metal ions in the bloodstream and tissues, preventing or reversing their harmful effects on cellular enzymes and proteins.
Current Medical Uses
Dimercaprol remains an important treatment for acute poisoning by specific heavy metals. It is an antidote of choice for acute arsenic, mercury, and gold poisoning. Its effectiveness is greatest when administered early, ideally within one to two hours of exposure.
For severe lead poisoning, dimercaprol is often used in combination with another chelating agent, edetate calcium disodium (CaNa2EDTA). In these cases, dimercaprol is given before CaNa2EDTA to help prevent lead redistribution to the central nervous system. While newer oral chelating agents like succimer have emerged for less severe cases, dimercaprol remains a valuable option, especially when the gastrointestinal tract is compromised.
Potential Side Effects
While effective, dimercaprol can cause several side effects. Pain at the injection site is a common complaint, as the medication is administered via deep intramuscular injection and is formulated in peanut oil. This can lead to localized pain or even sterile abscesses.
Patients may also experience systemic reactions, including nausea, vomiting, headache, and a feeling of tightness in the chest, throat, or hands. Cardiovascular effects such as increased blood pressure (hypertension) and a rapid heart rate (tachycardia) can occur, typically within 15 to 30 minutes after administration. A distinctive garlic-like odor on the breath is also a characteristic side effect. In children, fever is a common adverse reaction, affecting about 30% of pediatric patients.