Chelation Therapy
Definition
Administration of a polydentate ligand that forms a stable water-soluble complex with the metal cation and increases urinary excretion. BAL (dimercaprol) is the classical agent. DMSA (succimer) and DMPS (unithiol) are the modern oral agents. Ca-EDTA is specific for lead. Prussian blue is unique to thallium.
- Classical agent
- BAL (dimercaprol)
- Modern oral agents
- DMSA (succimer), DMPS (unithiol)
- Lead-specific
- Ca-EDTA
- Thallium-specific
- Prussian blue
- Mechanism
- Ligand forms water-soluble complex, raises urinary excretion
Common questions
Why does a chelation agent choice matter to a forensic toxicologist reconstructing a poisoning?+
Which chelator was administered, and when, changes the metal's blood and urine kinetics, so a toxicologist must know the treatment history before interpreting post-treatment metal levels, since chelation can rapidly lower blood concentration independent of the original dose.
Why is Prussian blue unique among these agents?+
Unlike the others, Prussian blue works in the gut rather than the bloodstream. It exchanges potassium for thallium ions and interrupts thallium's enterohepatic recirculation, which is why it is specific to thallium poisoning rather than a general heavy-metal chelator.
Related terms
- Bhasma
- Calcined heavy-metal preparation in classical ayurvedic and siddha pharmacopoeia. Includes naga bhasma (lead), parad bhasma (mercury), tamra bhasma (copper). Heavy metals are...
- Marsh Test
- Sensitive 1836 method for arsenic in which the acidified sample is added to zinc and dilute sulphuric acid. The evolved arsine gas...
- Mees Lines
- Transverse white bands across the fingernails that follow acute or repeated chronic exposure to arsenic, thallium or selenium. Appear 4 to 8...
- Reinsch Test
- Classical screen for arsenic, antimony, mercury and bismuth. A clean copper strip is immersed in the acidified sample (concentrated HCl, near-boiling) for...
- Speciation
- Determining the chemical form of a metal in a sample, not just the total. Critical for arsenic because As(III) trivalent arsenite is...