Sodium calciumedetate

Sodium calciumedetate is the calcium chelate of the disodium salt of ethylenediaminetetra-acetic acid (calcium EDTA). It is effective in acute lead poisoning because of its capacity to exchange calcium for lead the lead chelate is excreted in the urine, leaving behind a harmless amount of calcium. Dimercaprol may usefully be combined with sodium calciumedetate when lead poisoning is severe, e.g. with encephalopathy. 

In severe lead poisoning sodium calciumedetate is commonly used to initiate lead excretion. It chelates lead from bone and the extracellular space and urinary lead excretion of diminishes over 5 days thereafter as the extracellular store is exhausted. Subsequently symptoms (colic and encephalopathy) may worsen and this has been attributed to redistribution of lead from bone to brain. Dimercaprol is more effective than sodium calciumedetate at chelating lead from the soft tissues such as brain, which is the rationale for combined therapy with sodium calciumedetate. More recently succimer (2,3-dimercaptosuccinic acid, DMSA), a water-soluble analogue of dimercaprol, has been increasingly used instead. Succimer has a high affinity for lead, is suitable for administration by mouth and is better tolerated (has a wider therapeutic index) than dimercaprol. It is licenced for such use in the USA but not the UK. 

Synonyms calcium disodium edetate calcium disodium ethylenediaminetetraacetate calcium disodium (ethylene-dinitrilo)tetraacetate E385 edathamil calcium disodium edetic acid calcium disodium salt EDTA calcium ethylene-diaminetetraacetic acid calcium disodium chelate [(ethyl-enedinitrilo)tetraacetato]calciate(2-) disodium sodium calciumedetate Nersene CA. 

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