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Chelating agents:

chelating agents are Certain organic compounds capable of forming coordinate bonds (see chemical bond) with metals through two or more atoms of the organic compound; such organic compounds are called chelating agents. The compound formed by a chelating agent and a metal is called a chelate. A chelating agent that has two coordinating atoms is called bidentate; one that has three, tridentate; and so on. EDTA, or ethylenediaminetetraacetate, (-O2CH2)2NCH2CH2N(CH2CO2-)2, is a common hexadentate chelating agent. Chelating agents are important in textile dyeing, water softening, and enzyme deactivation and as bacteriocides. These are widely found in living systems and are of importance in cellular metabolism. For example, chlorophyll is a chelate of magnesium and hemoglobin is a chelate of iron.

  • Hydrophilic chelators most effectively promote renal metal excretion, but they complex intracellular metal deposits inefficiently
  • Lipophilic chelators can decrease intracellular stores but may redistribute toxic metals to,for example, the brain. In chronic metal-induced disease, where life-long chelation may benecessary, possible toxicity or side effects of the administered chelator may be limiting.
  • Natural chelators: water, carbohydrates, including polysaccharides, organic acids with more than one, coordination group, lipids, steroids, amino acids and related compounds, peptides, phosphates, nucleotides, tetrapyrroles, ferrioxamines, ionophores, such as gramicidin, monensin, valinomycin, phenolics etc. Chlorella, Activated charcoal, Cilantro being the natural chelators
  • Synthetic chelators: BAL, deferoxamine, deferiprone, DMPS, DMSA, D-penicillamine, DTPA, EDTA, tetrathiomolybdate, Prussian blue, etc.

 

Most commonly used chelating agents at our centre are:

EDTA , a synthetic amino acid is the most commonly used organic compound for Chelation Therapy. It is most effectively given as slow intravenous infusion over a period of 2-3hours EDTA was first used clinically in 1952, in USA for the treatment of a case of lead poisoning. Since then EDTA has been found to be useful in a large number of acute and chronic diseases. The American FDA has approved EDTA as the treatment of choice for lead poisoning, hypercalcemia, and ventricular arrhythmias in Digitalis toxicity.
EDTA forms stable complexes with metals like Calcium, Arsenic, Lead, Cadmium, Mercury, Nickel, Iron, Copper, etc. The relative stability of the EDTA-metal complex depends on the availability of the metal and its affinity for EDTA. The EDTA-metal complex is then flushed out of the system, mainly through urine.

DMSA, is a Thiol compound. It is mainly used as an oral chelating agent. It is primarily used for the chelation of Mercury, Lead and Arsenic.
DMSA easily crosses the cell membranes. It effectively removes Mercury from the blood, liver, brain, bones and large intestines.

 

The combined action of EDTA + DMSA

EDTA and DMSA combined have an excellent metal binding capacity especially for Mercury, Nickel, Aluminum , Lead. Cadmium and Manganese
That makes the combination useful for the treatment of neurological disorders such as Parkinson’s disease.
DMSA effectively detoxifies Central Nervous System. EDTA is useful for vascular problems and detoxifies other organ systems.

Other chelating agents(synthetic) are

DMPS, DMSA, DTPA, deferoxamine have gained more general acceptance among clinicians, undoubtedly improving the management of many human metal intoxications,including lead, arsenic, and mercury compounds. Deprivation of iron by chelating agents has been proposed as a method of cancer treatment, alongside the well-known mechanism of iron-promoted oxidative damage (e.g., Bleomycin).

  • Deferoxamine, Deferiprone -- chelates Iron
  • Pencillamine – Chelates copper
  • Prussian blue – Chelates Thallium
  • DTPA , DMPS, Trientine etc…