Ethylenediaminetetraacetic acid, widely abbreviated as EDTA (for other names, see Table) is a polyamino carboxylic acid and a colourless, water-soluble solid. Its conjugate base is named ethylenediaminetetraacetate. It is widely used to dissolve scale. Its usefulness arises because of its role as a hexadentate ("six-toothed") ligand and chelating agent, i.e. its ability to "sequester" metal ions such as Ca2+ and Fe3+. After being bound by EDTA, metal ions remain in solution but exhibit diminished reactivity. EDTA is produced as several salts, notably disodium EDTA and calcium disodium EDTA.
Lead poisoning and heavy metal toxicity
Chelation therapy using EDTA is the medically accepted treatment for lead poisoning. Injected intravenously and once in the bloodstream, EDTA traps lead and other metals, forming a compound that the body can get rid of in the urine. The process generally takes 1 - 3 hours. Other heavy metal poisonings treated with chelation include mercury, arsenic, aluminum, chromium, cobalt, manganese, nickel, selenium, zinc, tin, and thallium. Chelating agents other than EDTA are also used to clear several of these substances from the bloodstream.
Heavy metal toxicity in humans has been associated with many health conditions, including heart disease, attention deficit/hyperactivity disorder (ADHD), Alzheimer's disease, immune system disorders, gastrointestinal disorders (including irritable bowel syndrome, or IBS), and autism.
Digoxin toxicity
EDTA has also been used to treat digoxin toxicity, although most doctors prefer to use other methods. In this case, EDTA helps remove excess levels of digoxin, a medication that is used to treat abnormal rhythms of the heart.
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