After World War II, a large number of navy personnel suffered from lead poisoning as a result of their jobs repainting the hulls of ships. The medical use of EDTA as a lead chelating agent was introduced. Unlike BAL, it is a synthetic amino acid and contains no mercaptans. While EDTA had some uncomfortable side effects, they were not as severe as BAL.
In the 1960s, BAL was modified into DMSA, a related dithiol with far fewer side effects. DMSA quickly replaced both BAL and EDTA, becoming the US standard of care for the treatment of lead, arsenic, and mercury poisoning, which it remains today.
Research in the former Soviet Union led to the introduction of DMPS, another dithiol, as a mercury-chelating agent. The Soviets also introduced ALA, which is transformed by the body into the dithiol dihydrolipoic acid, a mercury- and arsenic-chelating agent. DMPS has experimental status in the US FDA, while ALA is a common nutritional supplement.
Other chelating agents have been discovered. They all function by making several chemical bonds with metal ions, thus rendering them much less chemically reactive. The resulting complex is water-soluble, allowing it to enter the bloodstream and be excreted harmlessly.
EDTA chelation is approved by the U.S. Food and Drug Administration (FDA) for treating lead poisoning and heavy metal toxicity.
Chelation therapy is used as a treatment for acute mercury, iron (including in cases of thalassemia), arsenic, lead, uranium, plutonium and other forms of toxic metal poisoning. The chelating agent may be administered intravenously, intramuscularly, or orally, depending on the agent and the type of poisoning.
One example of successful chelation therapy is the case of Harold McCluskey, a nuclear worker who became badly contaminated with americium in 1976. He was treated with diethylene triamine pentaacetic acid (DTPA) over many years, removing 41 MBq (1.1 mCi) of americium from his body. His death, 11 years later, was from unrelated causes.
Several chelating agents are available, having different affinities for different metals. Common chelating agents include:
Chelation therapy was used by the British after World War II to remove arsenic, lead, and other metals. Patients' conditions improved as these metals were removed from their bodies. Treatment may be applied to the skin via a transdermal patch. Another treatment is administered intravenously, a process that takes 2-3 hours, costs about $100 per treatment, and 20-30 treatments are often required.
Some common chelating agents are EDTA (ethylenediaminetetraacetic acid), DMSA (sodium 2,3 dimercaptopropane-1 sulfate), TTFD (thiamine tetrahydrofurfuryl disulfide), and DMPS (2,3 dimercaptosuccinic acid). EDTA and DMSA are only approved for the removal of lead by the Food and Drug Administration while DMPS and TTFD are not approved by the FDA. These drugs bind to heavy metals in the body and prevent them from binding to other agents. They are then excreted from the body. The chelating process also removes vital nutrients such as vitamins C and E, therefore these must be supplemented.
The American Heart Association states that there is currently "no scientific evidence to demonstrate any benefit from this form of therapy" and that the "United States Food and Drug Administration (FDA), the National Institutes of Health (NIH) and the American College of Cardiology all agree with the American Heart Association" that "there have been no adequate, controlled, published scientific studies using currently approved scientific methodology to support this therapy for cardiovascular disease." Atwood et al. consider that methodological flaws and lack of prior probability make this trial "unethical, dangerous, pointless, and wasteful."
In 2003, the Supreme Court of Missouri, in State Board of Registration for the Healing Arts v. McDonagh, 123 S.W.3d 146, overturned a decision of the State Board of Registration sanctioning a doctor who used chelation therapy for the treatment of heart disease. The Court held that the therapy was not harming patients, and the standard for determining repeated negligence in using an alternative therapy such as chelation is not whether it is popular or commonly accepted by the medical community, but rather whether heart specialists would consider its use to be reasonable.
In 1998, the U.S. Federal Trade Commission (FTC) charged that the web site of the American College for Advancement in Medicine (ACAM) and a brochure they published had made false or unsubstantiated claims. In December 1998, the FTC announced that it had secured a consent agreement barring ACAM from making unsubstantiated advertising claims that chelation therapy is effective against atherosclerosis or any other disease of the circulatory system.
Chelation therapy can be hazardous. In August 2005, botched chelation therapy killed a 5-year-old autistic boy, a nonautistic child died in February 2005, and a nonautistic adult died in August 2003. These deaths were due to cardiac arrest caused by hypocalcemia during chelation therapy.
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