Chelation Therapy

Notes

Definition

Chelation therapy is the administration of chelating agents to remove heavy metals in the body. It is very helpful in cases of poisoning and the most common forms of metal intoxication such as lead, mercury and arsenic poisoning. Chelating agents combine with metals and allow them to be excreted from the body.

Indications of chelating therapy:
  • Mercury poisoning
  • Iron poisoning
  • Arsenic poisoning
  • Lead poisoning
  • Uranium
  • Plutonium and
  • Other forms of heavy metals
Mechanisms of Action

The human body is unable to break down heavy metals. When these elements build up and reach toxic levels in the body it can interfere with the normal functioning of a person. Chelating agents lower the blood levels of metals (e.g. lead, iron, etc.). This is made possible by the attachment of heavy metal molecules to the administered chelating agents. The heavy metal attached to the chelating drugs is then removed in the body through urination.

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Common Chelating Agents
Chelating Agent Indication for use
Dimercaprol (BAL) Acute arsenic poisoningAcute mercury poisoningLead poisoning (with another chelating drug, EDTA)
Edetate calcium disodium orEthylenediamine tetraacetic acid (CaEDTA or EDTA) Lead poisoning
Deferoxamine Acute Iron poisoningIron overload
Dimercaptosuccinic Acid (DMSA) Lead poisoningArsenic poisoningMercury poisoning
Dimercapto-propane sulfonate (DMPS) Severe acute arsenic poisoningSevere acute mercury poisoning
Penicillamine Copper toxicity (mainly used)Adjunct to the therapy in:

  • Gold poisoning
  • Arsenic poisoning
  • Lead poisoning
Succimer (Chemet) Lead poisoning in pediatric patients with blood lead levels above 45 microgram per deciliter
Side Effects
  1. Burnings sensation at the site of injection or delivery into the vein (common)
  2. Fever
  3. Headache
  4. Nausea
  5. Stomach upset
  6. Vomiting
  7. Flu-like symptoms
  8. Convulsions
  9. Bone marrow depression
  10. Hypotension
  11. Cardiac arrhythmia
  12. Respiratory arrest
  13. Hypocalcemia
  14. Kidney failure (rare)
  15. Death (rare)
Contraindications
  • Hypersensitivity or known allergy to the drugs
Nursing Implications
  1. Obtain serum levels of heavy metals (e.g. lead, iron) before the initiation of therapy and again at the termination of the therapy.
  2. Instruct the parents and child about the need to comply with the full course of medication regimen to achieve desired outcome and effectiveness.
  3. For EDTA: Monitor serum calcium levels as EDTA removes calcium in the body.
  4. For EDTA: Injections of EDTA must be given intramuscularly into a large muscle mass. The medication can be combined with 0.5 ml of PROCAINE as the injection of this drug is very painful.
  5. Measure intake and output to ensure that the kidney is adequately functioning. (If kidney function is not adequate EDTA may lead to nephrotoxicity or kidney damage)
  6. Assess the following:
    • BUN
    • Serum creatinine
    • Protein in urine