Dimercaprol

What it is and how it works

Dimercaprol (British anti-Lewisite, BAL) is a dithiol compound whose sulfhydryl groups form stable chelates with arsenic, mercury, gold and lead, preventing them from binding to tissue enzymes and promoting their urinary and biliary excretion.

Indications

Acute poisoning by arsenic, mercury and gold; used with sodium calcium edetate in severe lead poisoning, including lead encephalopathy.

Dosage and administration (summary)

By deep intramuscular injection, typically 2.5–3 mg/kg every 4 hours for 2 days, then 2–4 times on the third day, then once or twice daily for up to 10 days or until recovery; regimens are adjusted to the metal and severity.

Contraindications

Hepatic impairment (unless due to arsenic poisoning); poisoning with iron, cadmium or selenium, as the chelates formed are more toxic; known peanut (arachis oil) allergy.

Warnings and precautions

Adverse effects such as hypertension, tachycardia, nausea, headache, burning sensations and lacrimation are common and dose-related. Urine should be kept alkaline to protect the kidneys from dissociation of the chelate; use with caution in renal impairment and in G6PD deficiency because of the risk of haemolysis. Injection is painful and may cause sterile abscess.

Pregnancy

Use only if clearly necessary in serious poisoning.

Storage and supply

Store below 25 °C, protected from light.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.