Drugs acting on skin and mucous membrane.pptx

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1. Drugs acting on skin and mucous membrane S.Narvin

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

3. Demulcents Demulcents are inert substances which sooth inflamed or uncovered mucosa or skin by preventing contact with air/irritants in the surroundings. A pplied as thick colloidal/viscid solutions in water. Examples Glycyrrhiza is a sweet tasting root used in cough lozenges to sooth the throat and as sweetening/ flavouring agent in mixtures Methylcellulose - nose drops and contact lens solutions. Propylene glycol - cosmetics and as occlusive dressing Glycerine - has dehydrating property

4. EMOLLIENTS 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. Olive oil, arachis oil, sesame oil, cocoa butter, hard and soft paraffin, liquid paraffin, wool fat, bees wax are the commonly employed emollients. They are also used as vehicles for topically applied medicaments and as ointment bases. Wool fat may cause allergy in some patients.

5. ADSORBANTS AND PROTECTIVES Adsorbants are finely powdered, inert and insoluble solids capable of binding to their s urface (adsorbing) noxious and irritant substances. They are also called protectives because they afford physical protection to the skin or mucosa 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.

6. Astringents 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. 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.

7. IRRITANTS AND COUNTER-IRRITANTS 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. 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 .

8. Mechanism of counterirritation 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 obscure the deeper sensation. Irritation of afferent nerve endings produces arteriolar dilatation in the adjoining areas of skin by axon reflex (which mediates flare in triple response). Through segmental association of afferents, vasodilatation also occurs in the corresponding deeper organ. 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 (torticollis, backache, sprain), joint pain, pleural/peritoneal pain, colics , etc.

9. Counter Irritants 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