External preparationsPhar 401

Biology of the skin

Glabrous skin- on palms and soles of the feet, lacks hair follicles and sebaceous glandsHairy skin- has hair follicles and sebaceous glands

Functions of skin• Control the lost of valuable water from the body• Protect the body from the harmful radiations of the sun• Control the entry of foreign materials• Prevent the entry of harmful microorganisms• Cushion the body against the mechanical shock from bumps and

knocks• Regulate the loss of heat from the body• Receive information from the environment and relay it to the brain.• By its color, texture and odor, transmit social and sexual signals to

others.• It must last a lifetime. It must maintain itself against the ravage of

wear and tear.• It must always fit. It must grow as its owner grows and be resilient

and elastic to stretch and contract to allow the body freedom of movement.

Diagrammatic structure of skin

Common skin problem

1. Dry skin/ Oily skin2. Wounds and infection

Acne vulgaris

• Excess sebum+keratinization forms occlusive plug in the pores – accumulation of stagnant sebum – proliferation of anaerobic bacteria – bacteria produce lipase enzyme that hydrolyse the triglycerides in the sebum to produce free fatty acids and glycerol – irritation – hyperkeratinization and inflammation

Major Action of external preparations

• Occlusive • Emollient• Astringent• Lubricant• Rubefacient

Types of skin preparation

1. Solids-Dusting powder

2. Liquids-Soaks-Liniments-Paints-Collodions

3. Semi-solids-ointment-cream-paste

Cream

Ointment

Ingredients used in skin preparation1. Water miscible vehicles

Eg. Water, alcohol, macrogols2. Oily vehicles

Eg. Mineral oil- paraffin Vegetable oil- castor, peanut Synthetic oil- silicone oil

3. Emulsifying agentsEg. Natural, syntheticw/o emulsifier- wool fat, beewaxo/w emulsifier- cetostearyl alcohol, surfactants

4. Suspending agentsEg. Bentonite, veegum(Aluminium Magnesium Silicate)Gelling agent- tragacanth, alginates, gelatin, methylcellulose

5. OtherEg. Wetting agents- tincture of quillaia Humectants- glycerol, propylene glycol Solids- ZnO, starch, talc, aerosil

Semi-solid preparation

Mixing by fusionMixing by trituration

Mixing by fusion

• Blending together of oily materials, some of which are solids at room temperature.

Keep ingredients in evaporating basin heat melt remove the basin from waterbath gently stir until cold.

• If soluble and stable, add when the base is molten• If insoluble or less stable, add during cooling or when cold.

Mixing by trituration

• Insoluble solid or liquid medicaments are incorporated into bases using this technique

Pass powder by 180µm sieve place them on tile/slab mix with base by doubling up (base:powder=2/3:1)

• If larger quantities of liquid should be used, use mortar with flat base using a pestle with flat head.

Tube filling machine

Dispensing

Dusting powder• Powder should be sterile if they may be applied to large areas

of open skin or wounds.• To prepare powders for external use, sieve size of 180µm

should be used to obtain the finely divided powder.

- “ for external use only”- “Store in cool and dry place”- “ Not to be applied to open wounds or raw

weeping surfaces”

Liquid preparation“For external use only”“Shake well before use”

“ Store in cool place”“expiry date”

Semi-solid preparations“ Store in cool place but donot allow to freeze”

“expiry date”

Containers

The end