edetate calcium disodium + dimercaprol

This combination therapy is specifically indicated for severe lead poisoning, particularly when blood lead levels exceed 70 mcg/dL or when symptoms of lead encephalopathy are present[6]. The rationale for using these agents together is that edetate calcium disodium alone may increase lead redistribution into the brain and potentially worsen encephalopathy, while dimercaprol helps prevent this redistribution[5][6]. Dimercaprol works by forming stable chelates with heavy metals like lead, mercury, arsenic, and gold through its sulfhydryl groups, allowing these metals to be excreted in urine[8]. Edetate calcium disodium forms stable chelates with divalent and trivalent metals (including lead) that can displace calcium in the molecule, with the resulting chelate being excreted in urine[3]. When used in combination, these agents decrease blood lead levels more rapidly than either agent alone, though the final post-chelation blood lead levels may be similar to monotherapy[5]. The combination is particularly important in severe cases to prevent the risk of encephalopathy that can occur with edetate calcium disodium monotherapy. For acute lead encephalopathy, the typical regimen involves: - Dimercaprol: 4 mg/kg IM every 4 hours, with the first dose given alone - Edetate calcium disodium: Added starting with the second dose of dimercaprol, at a total daily dose of 1,000 mg/m² given every 8-12 hours IM or once daily IV over an 8-12 hour interval[5] For less severe toxicity, the dimercaprol dose can be decreased to 3 mg/kg after the first dose. Treatment typically continues for 2-7 days depending on clinical response, including decreased blood lead levels, reversal of hematologic effects, and increased urinary lead excretion[5][7]. The combination therapy has been associated with increased side effects compared to monotherapy, particularly elevated liver enzymes and vomiting[5]. Dimercaprol should not be used in patients with hepatic insufficiency (except in cases of arsenical jaundice) and should be used with caution in patients with renal impairment[8]. Edetate calcium disodium is contraindicated during periods of anuria and in patients with active renal disease or hepatitis[6]. Both medications require careful monitoring of urine output throughout therapy, and treatment should be stopped if anuria or severe oliguria develops[6][8].

Other names

calcium disodium edetate + dimercaprolCaNa₂EDTA + BALedetate calcium disodium + British anti-Lewisite