Chelation therapy involves the administration of chelating agents to treat toxic metal poisoning. These chelating agents or chelants are used to remove heavy metals from the body in cases of overdose, poisoning or accumulation. The chelants are ligands that bind to metals present in the blood and tissues.
They form complexes called chelates that are chemically inert and can be easily be excreted without interacting any further with the body. In this way, chelation therapy detoxifies poisonous metals such as arsenic, lead or mercury. Depending on the agent used and the type of metal intoxication, chelating agents may be taken orally or injected into a vein or muscle.
Uses of chelation therapy
Some examples of clinical scenarios where chelation therapy is indicated include:
- Poisoning with heavy metals including lead, mercury, and arsenic
- Overdose of medications containing metal ions
- Accumulation of large amounts of iron in the body due to repeated blood transfusions, such as in the case of thalassemia patients who require frequent blood transfusions.
- Accumulation of large amounts of copper in the body due to Wilson's disease, a condition where the body is unable to excrete copper normally.
Several studies have been conducted to test the effects of chelation therapy in other disorders such as cancer, heart disease and autism. However, no solid evidence to support use of the therapy for these conditions has yet been found.
Some examples of chelating agents include:
- One of the first chelators was the organic dithiol compound dimercaprolt, which was developed as an antidote to an arsenic-based chemical warfare agent called lewisite. The agent is also known of as British anti-Lewisite or BAL.
- One of the most common chelants used to treat lead, mercury or arsenic poisoning is dimercaptosuccinic acid (DMSA). DMSA is a modified version of BAL that was developed in the 1960s and has far less side effects than BAL.
- Dimercapto-propane-sulfonate (DMPS) acts as an arsenic and mercury chelator.
- Alpha lipoic acid (ALA) is a nutritional supplement that transforms into dithiol dihydrolipoic acid, a chelator of both mercury and arsenic.
- Ethylenediamine tetraacetic acid (EDTA) is a lead and mercury chelating agent. Calcium ethylenediamine tetraacetic acid (CaNaEDTA) is given as an injection to treat severe lead poisoning.
- D-Penicillamine is used to chelate and remove copper and is a useful treatment for patients with Wilson's disease.
- Deferoxamine and deferasirox are chelating agents that help remove excess iron from the body. These agents may be used to treat cases of iron poisoning and are also useful in the treatment of thalassemia patients who are prone to iron overload due to frequent blood transfusions.
Reviewed by Sally Robertson, BSc