Introduction to Dimercaprol
Dimercaprol, also known as British Anti-Lewisite (BAL), is a chelating agent used in the treatment of heavy metal poisoning. It was originally developed during World War II as an antidote for chemical warfare agents, specifically
Lewisite, an arsenic-based compound. Today, it is primarily used to treat poisoning from arsenic, mercury, lead, and other heavy metals.
Mechanism of Action
Dimercaprol works by binding to the heavy metals in the body, forming stable complexes that can be excreted through the kidneys. It contains two sulfhydryl groups, which are crucial for chelating metals. These
sulfhydryl groups interact with the metal ions, reducing their toxicity and preventing them from binding to essential cellular components.
Clinical Applications
The primary use of dimercaprol is in cases of acute heavy metal poisoning. It is effective against arsenic, inorganic mercury, and lead. However, its use is often limited to severe cases due to its side effects. In the case of
lead poisoning, it is often used in combination with other chelating agents like EDTA (ethylenediaminetetraacetic acid) for enhanced efficacy.
Adverse Effects
Despite its effectiveness, dimercaprol is associated with several adverse effects. Patients may experience hypertension, tachycardia, nausea, vomiting, and a burning sensation in the mouth. It can also cause pain at the injection site, as it is administered intramuscularly. These side effects limit its use to situations where no other safer alternatives are available.
Alternative Chelating Agents
Due to the side effects associated with dimercaprol, other chelating agents are often considered. For example,
succimer (DMSA) is an oral chelating agent used for lead poisoning in children and has fewer side effects. For mercury poisoning,
penicillamine is another alternative. These agents are preferred in cases where the patient's condition allows for a less aggressive treatment approach.
Contraindications and Precautions
Dimercaprol should not be used in patients with known hypersensitivity to the drug. It is also contraindicated in patients with severe hepatic impairment due to its metabolism in the liver. Caution is advised in
patients with hypertension or renal impairment, as the drug can exacerbate these conditions. Close monitoring is essential during treatment to manage any adverse reactions promptly.
Pharmacokinetics
Dimercaprol is rapidly absorbed after intramuscular administration, with peak plasma concentrations occurring within 30 to 60 minutes. It is metabolized in the liver and excreted primarily in the urine. The half-life of dimercaprol is relatively short, necessitating frequent dosing to maintain therapeutic levels.
Conclusion
Dimercaprol remains an important treatment for acute heavy metal poisoning, despite its adverse effects. Its development marked a significant advancement in toxicology and the management of heavy metal exposure. However, the availability of alternative chelating agents with improved safety profiles has reduced its use in modern clinical practice. Nevertheless, understanding its mechanism, applications, and limitations remains crucial for toxicologists and healthcare providers dealing with toxic exposures.