Chelation therapy

1. Complexing and
Chelating Agents
By – Sahaya Asirvatham

2. What is Chelation???
 Chelation (KEE-LAY-SHUN)
comes from the Greek word –
“chele”- which means CLAW
 “the use of a chelating agent to
bind with a metal in the body to
form a chelate so that the metal
loses its toxic effect or
physiological activity”

3. CHELATION- CLAW-LIKE
FORMATION

4. Common Uses of Chelation
Therapy
 Chelation therapy has primarily been used as
agent to detoxify heavy metals such as calcium,
iron, magnesium, lead and zinc.
 Binds to these metal ions because of its strong
affinity for cations.
 The bound metal ions are then excreted in the
urine.

5. LIGANDS
Ligand is an ion or molecule (functional group)
that binds to a central metal atom to form a
coordination complex.
The bonding between metal and ligand generally
involves formal donation of one or more of the
ligand's electron pairs.

6. MOA
• Heavy metals exert their toxic effects by combining with
and inactivating functional groups (ligands) of enzymes
and important biomolecules - sulfhydril, hydroxyl,
carboxyl etc. leading to inactivation
METAL
ENZYME
COMPLEXING
AGENT
NO TOXIC
EFFECT

7.  Chelating agents compete with body ligands for the
heavy metal – also differ in affinity for different
metals
 • Chelating agents have high affinity for such metals
and combine with them to form non toxic and water
soluble complexes for elimination
 • Possesses: –ve charged groups to attract +ve
charged toxic metals

9. Ideal chelating agent
1. Ideal chelating agents have higher affinity for
toxic metals than for body Ca++ (readily
available in plasma and ECF)
2. Should also have higher affinity for toxic metals
than body ligands
3. Ideally should be water soluble
4. Interval of administration between exposure to
metals and chelating agents should be less

10. Chelating Agent
Classification
1. Penicillamine – Cu, Pb, Hg, Zn
2. Disodium edetate (EDTA) – lead poisoning
3. Dimercaprol (British antilewisite) or BAL –
As, Au, Bi, Ni, Sb and Hg poisoning

11. Penicillamine -------- Degraded product of Penicillin (beta
dimethylcysteine)
Prepared by alkaline hydrolysis of benzyl penicillin – d-
penicillamine
Strong Cu chelating property - useful in Cu poisoning
MOA is same as others – selective chelating of Cu, Hg, Pb and Zn
Absorbed orally - available as 250 mg capsules, metabolized in liver
and excreted in urine
Penicillamine

12. PenicillamineUses
 Wilson`s disease: Hepatolenticular degeneration due
to genetic deficiency of ceruplasmin (Cu deposition in
body) – life long therapy (0.5-1 gm daily)

13.  Cu and Hg (alternative) Poisoning
 Chronic Pb poisoning (adjuvant to edetate)
 Cystinuria and cystine stones
 Scleroderma: benefits by increasing soluble
collagen

14. BAL or Dimercaprol
 World War-II as British anti-Lewisite ---- Arsenical Gas
 Oily , pungent smelling, viscous liquid, water soluble