local acting substances chelating agents
TRANSCRIPT
Local acting substances
&Chelating agents
Dr Sameh AM Abdelghany
Mansoura Faculty of medicineClinical Pharmacology Department
Local acting Substances
Definition substances used mainly for their local
actions. act by mechanical, physical and/or
medical basis of action.
Emollients
CounterirritantsIrritants
Types
Melanizing Demenizing
AdsorbentsDemulcents
Astringents
Keratolytics
I- DEMULCENTS
Definition: are inert substances of high MW
applied over injured skin or mucous membranes to protect them by forming sticky, viscid layer.
Examples: egg white, milk, honey, licorice, and
glycerin.Uses: oTreatment of conjunctivitis oTreatment gastroenteritis e.g. milk in
peptic ulcer
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.
III- AdsorbentsDefinition: are insoluble powders that can
adsorb water and toxins on their surfaces.
Examples: talk powder, activated charcoal,
kaolin, pectin, etc.
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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.
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IV- ASTRINGENTSDefinition: 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.
Uses:1. Treatment of burns, wounds, ulcers
and conjunctivitis (zinc sulfate).2. To stop surface bleeding (silver
nitrate).
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 skinii. Caustics: they produce destruction of the tissue at
the site of application.
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.
VI- Counter-irritantsDefinition: 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.
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.
VII- KeratolyticsDefinition: drugs that soften
keratin and cornified skin.
Examples: salicylic acid.Uses: treatment of warts.
VIII- Melanizing agentsDefinition: drugs that stimulate synthesis
of melanin pigment e.g. khellin.
Uses: treatment of vetilligo.
IX- Demelanizing agentsDefinition: drugs that inhibit synthesis of melanin
pigment.
Uses: treatment of hyperpigmentation.
CHELATING AGENTS
Definition
are organic compounds used to chelate and eliminate metal ions by forming non-toxic complexes with them.
Dimercaprol (BAL): it contains 2 -SH groups that combine
with heavy metals and prevent them to combine with SH-containing enzymes in the body.
Uses: arsenic, mercury, and antimony poisoning.
d-penicillamine
similar to BAL but has one SH group.
Uses: 1. To chelate copper in Wilson’s disease.2. To chelate zinc in rheumatoid arthritis.
Ethylene diamine tetraacetic acid (EDTA)
can chelate Ca++ and lead.
Desferroxamine: chelate iron.