Local acting substances and different chelating agents

1. Local acting substances
&
Chelating agents
Dr Sameh AM Abdelghany
Mansoura Faculty of medicine
Clinical Pharmacology Department

2. Local acting Substances

3.  Definition
 substances used mainly for their local
actions.
 act by mechanical, physical and/or
medical basis of action.

4. Emollients
CounterirritantsIrritants
 Types
Melanizing Demenizing
AdsorbentsDemulcents
Astringents
Keratolytics

5. I- DEMULCENTS
Definition:
 are inert substances of high MW
applied over injured skin or mucous
membranes to protect them by
forming sticky, viscid layer.

6. Examples:
 egg white, milk, honey, licorice, and
glycerin.
Uses:
o Treatment of conjunctivitis
o Treatment gastroenteritis e.g. milk in
peptic ulcer

8. II- Emollients
Definition:
 are fats or oils used to soften the skin
and prevent its dryness.
Examples:
 olive oil, liquid paraffin, and cocoa
butter.
Uses:
 To soften skin and prevent its
dryness.

10. III- Adsorbents
Definition:
 are insoluble powders that can
adsorb water and toxins on their
surfaces.
Examples:
 talk powder, activated charcoal,
kaolin, pectin, etc.
www.themegallery.com

11. Uses:
1. Treatment of diarrhea (kaolin and
pectin).
2. Treatment of alkaloid poisoning e.g.
morphine poisoning (activated
charcoal).
3. Prevention of napkin dermatitis (to
adsorb moisture) e.g. talk powder.
www.themegallery.com

13. IV- ASTRINGENTS
Definition:
 are substances that precipitate
surface proteins to form protective
layer over injured skin and mucous
membranes.
Examples:
 alcohol, tannic acid, silver nitrate, and
zinc sulfate.

14. Uses:
1. Treatment of burns, wounds, ulcers
and conjunctivitis (zinc sulfate).
2. To stop surface bleeding (silver
nitrate).

16. V- Irritants
Definition:
 substances produce irritation of skin by
local or reflex action. According to the
degree of irritation, they classified into:
i. Rubefacients:
 they produce hyperemia of the skin
ii. Caustics:
 they produce destruction of the tissue at
the site of application.

17. Examples:
 Physical measures: heat application, short
wave and diathermy.
 Chemical measures: methyl salicylic acid
and camphor oil.
Uses:
1. To relief local pain as in arthritis, myositis,
nerve root pain, etc.
2. Caustics are used to remove excessive
granulation tissue and in dermabrasion.

19. VI- Counter-irritants
Definition:
 are substances applied to the skin to
produce local and reflex action.
i. Local irritant action:
→ VD and sensation of hotness → psychic
effect by diverting the attention of the patient
away from the diseased organ.

20. ii. Reflex action:
→ stimulation of cutaneous nerve that
converges with the visceral nerve at the
same spinal segment → block pain
sensation.
Uses:
1. To relieve pain of arthritis, myositis, or
visceral pain.
2. To relieve referred pain.

22. VII- Keratolytics
Definition:
 drugs that soften
keratin and cornified
skin.
Examples:
 salicylic acid.
Uses:
 treatment of warts.

23. VIII- Melanizing agents
Definition:
 drugs that stimulate synthesis
of melanin pigment
 e.g. khellin.
Uses:
 treatment of vetilligo.

24. IX- Demelanizing agents
Definition:
 drugs that inhibit synthesis of melanin
pigment.
Uses:
 treatment of hyperpigmentation.

25. CHELATING AGENTS

26.  Definition
 are organic compounds used to
chelate and eliminate metal ions
by forming non-toxic complexes
with them.

27.  Dimercaprol (BAL):
 it contains 2 -SH groups that combine
with heavy metals and prevent them
to combine with SH-containing
enzymes in the body.

28.  Uses:
 arsenic, mercury, and antimony poisoning.

29.  d-penicillamine
 similar to BAL but has one SH group.

30.  Uses:
1. To chelate copper in Wilson’s disease.
2. To chelate zinc in rheumatoid arthritis.

31. Ethylene diamine tetraacetic acid
(EDTA)
 can chelate Ca++ and lead.

32.  Desferroxamine:
 chelate iron.