Paper II — 2025 March (Supplementary) (2010 Scheme) — Q6

Paper II

2025 March (Supplementary) (2010 Scheme)

Question

Chelating agents

Q63 marksShort Notes★✓

Answer

Chelating agents bind metal ions to form stable, water-soluble complexes that are readily excreted, used as antidotes in heavy metal poisoning.

By metal:

• Lead: EDTA (edetate calcium disodium), Dimercaprol (severe cases), Succimer (DMSA — oral, an important advance over dimercaprol for outpatient/paediatric use, avoiding painful IM injection).
• Iron: Deferoxamine (parenteral).
• Copper (Wilson’s disease): Penicillamine, Trientine.
• Arsenic/mercury/gold: Dimercaprol (British anti-Lewisite, BAL).

MOA: form stable ring-shaped complexes with the metal ion (chelation), converting a toxic, tissue-bound form into an inert, water-soluble form excreted mainly by the kidney.

Adverse effects: hypotension and pain at injection site (dimercaprol), hypocalcemia (EDTA, if not given as the calcium-disodium salt), nephrotoxicity, and depletion of essential trace metals with prolonged use.

Related Concepts

1. 1Chelating Agents

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