dimercaprol

Dimercaprol is used as an antidote for poisoning from minerals including arsenic, gold, and mercury, and concomitantly with edetate calcium disodium to treat acute lead poisoning.

Dimercaprol was developed during World War II as an experimental antidote against the arsenic-based poison gas Lewisite. It is also used off-label for polonium poisoning and to treat Wilson disease, a rare genetic disorder that causes copper accumulation in the body.

Dimercaprol is a chelating agent, a chemical compound that reacts with metal ions to form stable, water-soluble metal complexes that can be excreted in the urine, thus preventing poisoning from the metals. The sulfhydryl groups of dimercaprol form complexes with metals such as arsenic, gold, mercury, and lead, preventing or reversing the metallic binding with sulfhydryl-containing enzymes in the body.

Dimercaprol is not orally absorbed, but it is also administered with a deep intramuscular injection that can be painful. Dimercaprol treatment usually is given for 10 to 15 days, because the sustained presence of dimercaprol promotes continued excretion of the metallic poisons. Dimercaprol has a toxic potential and can cause adverse reactions such as vomiting, convulsions, and stupor that usually resolve within 6 hours following the injection.

• Do not administer dimercaprol intravenously.
• Avoid administering dimercaprol to patients with hypersensitivity or allergy to peanuts or any of the components of dimercaprol.
• If dimercaprol is administered to patients with peanut allergy, medication and equipment necessary to treat allergic reactions should be available.
• Do not use in patients with liver insufficiency, except postarsenical jaundice.
• Do not use to treat iron, cadmium or selenium poisoning, dimercaprol can form complexes more toxic than the metals, particularly to the kidneys.
• Dimercaprol should be used concurrently with edetate calcium disodium for acute lead poisoning, because dimercaprol as a single agent can increase lead’s neurotoxic effects.
• Use dimercaprol with caution in patients with the genetic disorder G6PD deficiency.
• Use with caution in patients with low urine output (oliguria) and discontinue if kidney failure occurs.

Common side effects of dimercaprol include:

• High blood pressure (hypertension)
• Rapid heart rate (tachycardia)
• Chest pain
• Headache
• Fever in children
• Burning sensation in the lips, mouth and throat
• Tightness and/or pain in the throat, chest or hands
• Inflammation of the conjunctiva, the membrane over the eye whites and inner eyelid surfaces (conjunctivitis)
• Spasm of eyelids (blepharospasm)
• Watering eyes (lacrimation)
• Nasal discharge (rhinorrhea)
• Nausea
• Vomiting
• Salivation
• Throat swelling and irritation
• Sore throat
• Abdominal pain
• Tingling of hands (paresthesia)
• Anxiety
• Nervousness
• Weakness
• Burning sensation in the penis
• Excessive sweating (diaphoresis)
• Pain at injection site
• Painful sterile abscesses
• Kidney insufficiency
• Low count of leukocyte immune cells (leukopenia)

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

• Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
• Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
• Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
• Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

Injectable Solution

• 100 mg dimercaprol-210mg benzyl benzonate-680mg peanut oil/mL

Adult and Pediatric:

Arsenic/Gold Poisoning

• Day 1-2: 10-12 mg/kg/day divided every 6 hours deep intramuscularly (IM) for 2 days
• Day 3: 5-6 mg/kg/day divided every 12 hours deep IM for 1 day
• Day 4-14: 2.5-3 mg/kg deep IM once daily for 11 days
• Severe gold dermatitis: 2.5 mg/kg IM every 4 hours for 2 days, then twice daily for 1 week
• Gold-induced thrombocytopenia: 100 mg IM twice daily for 15 days

Mercury Poisoning

• Day 1: 5 mg/kg deep IM once daily for 1 day
• Day 2-11: 2.5 mg/kg deep IM every 12-24 hours for 10 days

Lead Poisoning

• Initial 4 mg/kg (75-83 mg/sq. meter) IM
• Repeat dose at least 4 hours later (but not until adequate urine flow is established), THEN
• 4 mg/kg (75-83 mg/sq. meter) and ethylenediaminetetraacetic acid (EDTA) 250 mg/sq. meter IM every 4 hours for 3-5 days
• If blood lead concentration rebounds to greater than 45 mcg/dL [2.174 micromoles/L] within 5-7 days, may repeat the course of treatment (usually just EDTA without dimercaprol)

Wilson Disease (Off-label)

• Rarely used because of deep IM injection of 2-3 mL that is painful
• 2.5-3 mg/kg IM twice daily/three times daily

Dosing considerations

• Adjust dose to achieve urinary copper excretion of 0.5-1 mg/day
• Free copper levels in serum: Maintain at less than10 mcg/dL

Other Information

• Preadministered antihistamines may decrease side effects

Other Indications and Uses

• Do not use in iron, cadmium, or selenium due to the formation of toxic complexes
• Use with other agents (calcium-sodium-EDTA) in acute lead poisoning

Overdose

• Dosage above 5 mg/kg causes vomiting, convulsions, and stupor starting within 30 minutes of dimercaprol injection. Symptoms subside within 6 hours after the injection.

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Severe interactions of dimercaprol include:
  • Multivitamins, iron salts and iron preparations (can enhance their toxic effect)
• Dimercaprol has no listed serious, moderate or mild interactions with other drugs.

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider about all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or healthcare provider if you have any questions about the medication.

• There are no animal or human reproductive studies on dimercaprol and it is not known if it can affect the reproductive capacity or cause fetal harm. Dimercaprol should be administered to a pregnant woman only if it is clearly needed.
• It is not known if dimercaprol is present in breast milk. Use with caution in nursing mothers, because most drugs are excreted in breast milk.