This document summarizes different types of drugs acting on the skin and mucous membranes. It discusses demulcents, which soothe inflamed skin and mucosa; emollients, which soften and moisturize dry skin; adsorbants and protectives, which bind irritants on the skin's surface; astringents, which toughen the skin's surface; and irritants and counter-irritants, which stimulate nerve endings and induce localized inflammation or a remote effect to relieve deeper pain. Examples of commonly used drugs in each category are provided.

1. DRUGS ACTING ON
SKIN AND MUCOUS
MEMBRANE
S.Narvin

2. ◦ Demulcents
◦ Emollients
◦ Adsorbants and Protectives
◦ Astringents
◦ Irritants and Counter-Irritants

3. ◦ Demulcents are inert substances which sooth inflamed or
uncovered mucosa or skin by preventing contact with
air/irritants in the surroundings.
◦ Applied as thick colloidal/viscid solutions in water.

4. ◦ Examples
◦ Methylcellulose- nose drops and contact lens solutions.
◦ Propylene glycol- cosmetics and as occlusive dressing
◦ Glycerine- has dehydrating property

5. ◦ Emollients are bland oily substances which sooth and soften skin.
They form an occlusive film over the skin, preventing evaporation,
thus restoring elasticity of cracked and dry skin.
◦ They are also used as vehicles for topically applied medicaments
and as ointment bases.
◦ Wool fat may cause allergy in some patients.

6. ◦ Olive oil, arachis oil, sesame oil, cocoa butter, hard and soft
paraffin, liquid paraffin, wool fat, bees wax are the commonly
employed emollients.

8. ◦ Adsorbants are finely powdered, inert and insoluble solids capable of
binding to their surface (adsorbing) noxious and irritant substances.
◦ They are also called protectives because they afford physical protection
to the skin or mucosa

9. ◦ Examples
◦ Magnesium/zinc stearate
◦ Talc It is hydrous magnesium silicate, which spreads easily -used in talcum/face
powders.
◦ Calamine It is native zinc carbonate tinted pink with ferric oxide.-as cosmetic, on
sunburn, insect bite, urticaria and contact dermatitis.
◦ Starch It is used in dusting powders and for surgical glove.
◦ Aloe vera gel-Therapeutic claims in acne, psoriasis and many other conditions
have been made.

10. ◦ Astringents are substances that precipitate proteins, but do not
penetrate cells, thus affecting the superficial layer only.
◦ They toughen the surface making it mechanically stronger and
decrease exudation.

11. ◦ Tannic acid and tannins- They denature proteins forming protein tannate. Uses
are: Bleeding gums, Bleeding piles, Alkaloidal poisoning.
◦ Alcohol Ethanol and methanol are good astringents at 50–90% concentration.
Denatured spirit rubbed on the skin prevents bedsores. Ethanol is also used as
after-shave and on minor cuts.
◦ Mineral astringents Heavy metal ions are astringent and antiseptic. Alum has
been used as after-shave and as local haemostatic on minor cuts.

12. ◦ Irritants stimulate sensory nerve endings and induce inflammation at the
site of application.
◦ Depending on their nature, concentration and sensitiveness of the site,
they produce cooling sensation or warmth, pricking and tingling,
hyperesthesia or numbness and local vasodilatation.

13. ◦ Irritants which cause local hyperemia with little sensory component are called
Rubefacients.
◦ Stronger irritants which in addition increase capillary permeability and cause
collection of fluid under the epidermis (forming raised vesicles) are termed
Vesicants.
◦ Certain irritants that also produce a remote effect which tends to relieve pain
and inflammation in deeper organs are called Counter-irritants.

14. ◦ When a counter-irritant is applied to the area of skin supplied by nerves from the same
segment as the deeper organ from which pain impulses are coming, the cutaneous
impulses block the deeper sensation.
◦ Irritation of afferent nerve endings produces vasodilation in the adjoining areas of skin
by axon reflex.
◦ Increased blood supply helps to fight the cause of pain and inflammation in the deeper
organ.
◦ Counterirritants are generally rubbed to relieve headache, muscular pain , joint pain,
pleural/peritoneal pain,etc.

15. ◦ Clove oil- Applied by cotton swab for toothache.
◦ Eucalyptus oil- Used in pain balms.
◦ Camphor- Camphor produces cooling sensation- relieves itching.
Taken internally—small doses produce a warm and comforting
sensation in epigastrium; larger doses are emetic.
◦ Menthol- From mint or prepared synthetically, has cooling and
soothing action. It is added to pain balms, throat paints, throat
lozenges