Efi. Gelerstein 2011

Topic 29. Local therapy in dermatology

External drug therapy Topical preparations play an important part in the treatment of skin disease, and in body care and

cosmetics. Unilateral treatment or a different treatment for each extremity may be used to make it easier for the

treatment result to be assessed in one individual.

Percutaneous absorption A drug used on the skin must be dissolved or suspended in a vehicle (base). The drug of choice and the vehicle are both important and depend on diagnosis and state of the skin. The transfer of a drug from its vehicle to the horny layer depends on:

1. Age2. Hydratation3. Diseases4. Concentration gradient5. Temperature6. Intercellular lipids

Epidermal lipids Phospholipids (lower part of the epidermis) Neutral lipids (fatty acids, TG, fatty and esterified sterols, sphingolipides, ceramids) Cholesterol sulfate

Penetration of a drug through the skin depends on: Its concentration, The base, Its partition coefficient, Its diffusion constant, The thickness of the horny layer, The state, including hydration, of the horny layer, and Temperature

Shake lotion

Ointment

Cooling paste

Powder Liquid

Lotion

Cream

Cold cream

Paste

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Ointments Supple gels differing in consistency They usually consist of vegetable fats, animal fats, mineral oils and synthetic or semisynthetic

substances.1. Fats → generally well tolerated and may allow drugs to be absorbed by the deeper layers2. Petrolatum → particularly suitable vehicle where surface action is required. Petrolatum is

neutral, chemically indifferent, inexpensive3. Water-in-oil emulsions (W/O) → especially suitable for fat-soluble drugs and for water-

soluble agents where a slow, prolonged effect is desired.- These emulsions can absorb considerable quantites of water.

4. Oil-in-water emulsions (O/W) → particularly suitable for water-soluble drugs. These ointments are generally well tolerated, are hardly visible on the skin and easily washed off.- Water-soluble active substances may be passed on to deeper skin layers. Stability varies.

5. Mucilages 6. Synthetic substances

Powder Another base. It contains mineral substances, zinc oxide, titanium dioxide, talc, or vegetable substances. If powder and water are mixed and shaken, the result is a suspension.

The best-known shake lotion is made up of → equal parts of zinc oxide, talc, glycerol and water. There are a number of commercial shake lotions.

Shake lotions Shake lotions and pastes should not be applied to hairy areas; Lotio alba aquosa should not be used in body folds, such as genital region → may cause folliculitis. Pastes : These are mixtures of powders and unguents. The best known is zinc oxide paste. It consists

of ⅓ powder equal parts of zinc oxide and wheat starch and ⅔ unguent

Creams The addition of suitable solvents allows varying quantities of water to be introduced into ointments. This produces creams → if water content is high = lotions. There are two basic types of creams:

1. Oil-in-water emulsion 2. Water-in-oil emulsion

Cold creams and cooling paste Sol. aluminum acetate tartrate 1% (in 100g 20g) 1 % salicylic acid cold cream Indifferent cold cream Cooling paste

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Keratolytic effect1. Salicylic acid (5-40%)2. Lactic acid (6-12%)3. Sodium chloride (5-10%)4. Urea (10-20%)

Epithelialization effect1. Silver nitrate (0,5-1%)2. Salicylic acid (1-3%)3. Sodium chloride (3-5%)

Urea Effects ↑ horny layer hydratation ↑ penetration ↑ epithelialization Anti-pruritic Proteomuco and keratolytic effect

Dithranol (anthralin) Dithranol: 0,1-8 % Salicylic acid: 3 %

↓ epidermal proliferation Stimulates inflammatory response ↓ mitochondrial DNA production

Potency ranking of selected topical corticosteroids

Superpotent agents → Group I. Betamethasone dipropionate Halobetasol propionate Clobetasol propionate

Highly potent agents → Group II. Betamethasone dipropionate Mometasone furoate

Potent agents → Group III. Betamethasone dipropionate Betamethasone valerate Fluticasone propionate Fluocinolone acetonide Hydrocortisone valerate Hydrocortisone butyrate Hydrocortisone Mometasone furoate Triamcinolone acetonide

Steroid treatment

Efi. Gelerstein 2011

Effect: 1. Anti-inflammatory2. Anti-exsudative3. Anti-allergic4. Anti-proliferatíve5. Anti-pruritic

Side-effect: 1. Epidermal2. Connective tissue atrophy3. Fat tissue4. ↑ hair grow5. Produce vasoconstriction (later vasodilatation)6. Contact allergy

Indication of topical steroid treatment1. CDLE-SCLE (subacute cutaneous lupus erythematosus) - pic.2. Chronic eczema3. Psoriasis / Para-psoriasis4. Lichen5. Allergic and irritative contact dermatitis6. Atopic dermatitis / Seborrheic dermatitis7. Drug allergy / Insect allergy

Topical antibiotics1. Tetracycline2. Metronidazole3. Erythromycin4. Clindamycin5. Bacitracin6. Mupirocin

Diseases in which topical treatment is important Leg ulcers Eczema, dermatitis (mainly in atopic dermatitis) Seborrheic diseases → Acne, Rosacea Diseases caused by fungi Purulent skin infections Diseases caused by parasites Skin ageing

Good topical treatments help the effect of systemic therapy and can cause quicker improvement.