Chelation therapy for acute arsenic poisoning

Use for acute or subacute known or suspected arsenic poisoning without encephalopathy, coma, or severe cardiovascular side effect.

Oral: 10 mg/kg/dose (or 350 mg/m²/dose^*) every 8 hours for 5 days, followed by 10 mg/kg/dose (or 350 mg/m²/dose^*) every 12 hours for 14 days; maximum: 500 mg/dose.^¶

• For those with difficulty swallowing capsules (eg, young children), capsules can be opened and contents sprinkled on a small amount of soft food and swallowed immediately.
• Unit dose is 100 mg capsule. Each dose should be rounded to the nearest 100 mg.

Dermatologic: Rash, pruritus

Gastrointestinal: Nausea, vomiting, diarrhea, abdominal gas and pain

Hematologic: Thrombocytosis, eosinophilia, hemolysis in G6PD deficiency (medium risk)^[2]

Hepatic: Transient elevations of hepatic aminotransferases and alkaline phosphatase concentrations

Neurologic: Drowsiness, paresthesias

Respiratory: Rhinorrhea, sore throat

• Day 1: Every 6 to 8 hours
• Day 2: Every 8 to 12 hours
• Day 3 and thereafter: Every 12 to 24 hours^[1]

or

Regimen per product labeling (approved for mercury poisoning)

IV or IM^[3]:

• Day 1: 250 mg every 3 to 4 hours
• Day 2: 250 mg every 4 to 6 hours
• Day 3: 250 mg every 6 to 8 hours
• Day 4: 250 mg every 8 to 12 hours
• Day 5 and thereafter: 250 mg up to 1 to 3 times daily or transition to oral therapy

Oral^[4]: Initial (ie, has not received parenteral treatment): 1.2 to 2.4 g evenly spaced over 24 hours (eg, 100 to 200 mg every 2 hours), reduce dose based on symptoms and laboratory findings.

• Intravenous, deep IM, or oral.
• Oral bioavailability is 40% and may be used in less severe poisonings and after initial parenteral treatment once the patient is stabilized.

Dermatologic: Pruritus, toxic epidermal necrolysis

Hematologic: Risk in G6PD deficiency unknown^◊

Gastrointestinal: Nausea

Immunologic: Allergic reactions

Neurologic: Vertigo, weakness

Dimercaprol (also known as British Anti-Lewisite [BAL])

Currently not being manufactured

Use for severe known or suspected arsenic poisoning with encephalopathy, coma, and/or cardiovascular toxicity.

3 to 5 mg/kg IM every 4 to 6 hours.

In severe poisonings, 5 mg/kg IM every 4 hour has been used initially.^[1]

The goal is to transition from BAL to an oral chelator. If the patient is clinically improving but not able to take oral medications, tapering the dose is a reasonable option, such as 3 mg/kg for 2 days, then every 6 hours on day 3, followed every 12 hours for up to 10 days.

• Deep IM.
• Premedication with diphenhydramine recommended.
• Rotate injection sites.
• Maintain alkaline urine pH to protect kidneys.
• In kidney failure, HD may be required to remove arsenic chelate.

Formulation contains peanut oil; use with caution in peanut allergy

Cardiac: Chest pain, hypertension

Dermatologic: Diaphoresis

Gastrointestinal: Nausea, vomiting, salivation

Hematologic: Hemolysis in G6PD deficiency (high risk)^[1,2]

Local: Injection site pain, injection site sterile abscess

Neurologic: Headache

Ophthalmic: Lacrimation

Respiratory: Throat pain, rhinorrhea

Other: Febrile reaction, chelation of essential metals (prolonged course)