Heavy metals chelation therapy

Boyce N, Wood C, Holdsworth S, Thomson NM, Atkins RC. Life-threatening sepsis compUcating heavy metal chelation therapy with desferrioxamine. Aust NZ J Med 1985 15(5) 654-5. 

The -SH groups of dimercaptopropanol react with heavy metal ions including arsenic, to form very stable five-membered chelate rings, displacing heavy metal ions that would otherwise bind to essential -SH groups of enzymes such as succinoxidase and pyruvic oxidase. In this way, most of the enzyme activity can be restored if therapy is commenced soon after exposure. 

Penicillamine (Cuprimine), a derivative of penicillin, is officially classified as a chelating agent that is often used in the treatment of heavy metal intoxication (e.g., lead poisoning). In addition, this drug has been used in patients with severe rheumatoid arthritis, and seems to be as effective as other DMARDs such as methotrexate, sulfasalazine, and gold therapy.68 98 Penicillamine, however, tends to be substantially more toxic than other DMARDs, and is therefore used rarely in the treatment of specific patients with rheumatoid arthritis.68... 

Heavy Metal Intoxication Chelators), also binds aluminum and is being used as therapy for this disorder. 

Toxic heavy metals, such as cadmium, lead, and mercury, are sulfur seekers that bind strongly with thiol groups, which is one of the ways in which they interact adversely with biomolecules, including some enzymes. Advantage has been taken of this tendency to use thiols in chelation therapy in heavy metal poisoning. Among the thiols tested for this purpose are meso-2,3-dimer-captosuccinic acid, diethyldimercapto succinate, a-mercapto-P-(2-furyl), and a-mercapto-P-(2-thienyl) acrylic acid.3 The structural formulas for the first two are... 

Extracorporeal blood purification therapies do not efficiently remove heavy metals or their salts. Chelating agents can be combined with dialysis modalities and hemoperfusion to improve the clearance of aluminum, iron, and other metals. 

There is limited evidence to recommend combined chelation and blood purification therapy for other heavy metal poisonings, such as copper, mercury, arsenic, and thalhum. There are case reports, however, outlining several such attempts. Treatment of cupric sulfate ingestion by dimercaprol and penicillamine chelation followed by hemoperfusion and hemodia-filtration has been reported [57]. An interesting case of inorganic mercury poisoning treated with DMPS chelation and continuous venous-venous hemodiafiltration (CVVHDF) was also reported [58]. It should be noted that treatment continued for 14 days with a hmited total removal of mercury (<13% of the ingested dose) in... 

Some TCA masks have been presented as chelated TCA. Chelation is a medical therapy that aims to detoxify the body of harmful minerals and metals. Chemically, chelation is the process by which an organic substance (the chelator) binds metal ions (iron, copper, lead, calcium, etc.) into inactive, non-toxic and water-soluble complexes that are easily eliminated in the urine. Intravenous chelation therapy (e.g. with ethylenediamine tetra acetic acid, EDTA) is often used to treat poisoning with heavy metals, including lead. The use of the term chelation therefore seems inappropriate as far as TCA is concerned, and has no chemical basis since TCA is not a metal. The little information available states that chelation reduces the speed of penetration of TCA and therefore its depth of action. Might what we call chelation be partial inactivation of the TCA The directions of use for Accu Peel state that a process called chelation allows the TCA to reach an even depth at the same time as using lower concentrations of TCA . Might chelation, on the contrary, be a process that activates the TCA But how can TCA be activated ... 

No antidote is available. Chelation therapy may be appropriate for exposure to agents containing heavy metals. 

NAC seems to have some clinical usefulness as a chelating agent in the therapy of heavy-metal poisoning. (NAC effectively chelates Au, Ag and Hg.)... 

I. Pharmacology. Penicillamine is a derivative of penicillin that has no antimicrobial activity but effectively chelates some heavy metals such as lead, mercury, and copper. It has been used as adjunctive therapy after initial treatment with calcium EDTA (see p 440) or BAL (dimercaprol p 413), although its use has largely been replaced by the oral chelator sucdmer (DMSA, p 501) because of its poor safety profile. Penicillamine is well absorbed orally, and the penicillamine-metal complex is eliminated in the urine. No parenteral form is available. 

B. The medical treatment of occupational toxic illness should follow the general principles outlined earlier in this section and in Sections I and II of this book. In particular, the use of specific antidotes should be undertaken in consultation with a regional poison control center ([800] 222-1222) or other specialists. This is particularly true before chelation therapy is initiated for heavy metal poisoning. 

Dextran and its derivates have found some applications in the medical field. Dextran sulphate has anticoagulant properties similar to those of heparin. Recent studies show antiviral properties of the sulphate esters of dextran, particularly in the treatment of the human immunodeficiency virus.Oral dextran sulphate has been used in Japan against arteriosclerosis for 20 years without harmful side-effects. Mercaptodextran is discussed for therapy of acute heavy-metal poisoning because it has a higher affinity for heavy metal ions such as silver, mercuric, cupric and auric ions than most other thiols and chelating agents. The properties of mercaptodextran are of interest regarding environmental clean-up of heavy metal contaminations. ... 

For non-radioactive heavy metals such immobilisation may well negate or reduce the effects of chemical toxicity. However, immobilisation does not negate radiotoxic effects and, in fact, may exacerbate them by leading to alpha-particle emission within cells near chromosomal or nuclear material. In situations like these, human intervention using chelation therapy is required, the success of which involves targeting the... 

Ethanediaminetetraethanoic acid (Figure 13.17), usually just called EDTA or H4EDTA, is a widely used chelating agent (Figure 13.18). It is present in shampoos (Figure 13.19), fertilizers, cosmetics and soft drinks containing ascorbic acid and sodium benzoate to prevent formation of benzene. It is also used as a preservative in foods and cosmetics. EDTA is also used in chelation therapy to remove harmful heavy metals or their ions from the body. 

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