Lec 3 External preparations Flashcards
What is an ointment?
Oily vehicles with surgactant so can be washed off easily
- Used as emollients (soften tissues), for drug delivery to the surface or deeper penetration into skin
What are creams?
- Usually oil in water emulsions (oily creams are water in oil emulsions)
- Less greasy than ointments used for drug delivery onto or into skin
- High water content so require preservative
What are pastes?
- High concentration of added solids
- Makes them thick and localises drug delivery
Eg. Sun block
What are gels?
- Aqueous gels for lubrication or drug application to the skin
- Oily gets used for occulsion (excludes air, retains moisture, heat, body fluids and medicaments)
Application (definition, example, label)
- a liquid or semi-solid preparation for external use
Eg. Benzyl benzoate application - for external use only
Ear drops (definition, example, label)
- solution of medicament in water, glucerol, propylene glycol or diluted ethanol
Eg. Sodium bicarbonate ear drops - Caution: Not to be taken
Gel (definition, example, label)
- water-miscible, viscous preparations for application
Eg. Chlorhexidine gel - For external use only
Lotion (definition, example, label)
- liquid preps for application to skin without friction
Eg. Calamine lotion - For external use only
Paint (definition, example, label)
- Liquid prep for application in limited amounts to skin or mucous surface
Eg. Salicyclic acid paint - For external use only
Liniment (definition, example, label)
- Liquid or semi-liquid prep for external application containing analgesic, rubefacient, soothing or stimulating properties
Eg. Methyl salicylate compound liniment - For external use only, do not apply to broken skin
Paste (definition, example, label)
- Solid external prep with protective properties
Eg. Zinc paste - For external use only
Shampoo (definition, example, label)
- Liquid or soapy solution for scalp or body
Eg. Nizoral shampoo - Not to be taken. External use only
Suppository (definition, example, label)
- Solid unit dose shaped for rectal administration with medicament for local or systemic effect
Eg. Paracetamol suppository - For rectal use only, unwrap before use
Creams (definition, example, label)
- Semi-solid prep, usually emulsions for application to skin
Eg. Aqueous Cream - For external use only
Nose drops (definition, example, label)
- Liquid preparation for use in nasal possages
Eg. Otrivine - Caution: not to be taken
Ointments (definition, example, label)
- Semi-solid preparations used as emollients, protective preparations or to provide medicatment to skin
Eg. Emulsifying Ointment - For external use only
Where do medication on skin pass?
- Stratum corneum, hair follicles, sweat glands
- Lipid soluble -> lipid regions
- Water soluble -> enter blood capillaries
- Absorption occurs-> may cause toxicity
How does skin treatment work?
By drugs or by creating physiological changes
- normal skin 10-25% moisture
- evaporation = cooling (for inflammation)
What is it called when there is a lack of moisture on skin and what product is used?
Eczema
- Use occlusive, oily product as emollient
- Oitment to hydrate and soften the skin
What is it called when there is too much moisture on skin and what product is used?
Athlete’s foot
- Use astringent, non oily medicated cream
Name 3 water-miscible vehicles
- Water
- Alcohol (industrial denatured alcohol)
- Macrogols (liq/semi-solid to waxy solids)
Name 3 oily vehicles
- Minteral oils (paraffins) - soft paraffin
- Vegatable oils- castor, oil, peanut and coconut oils. Occlusive, skin penetration, may cause allergic reactions
- Synthetic oils water repellant and occlusive
Name 3 emulsifying agents and describe
- Oil in water: emulsifying waxes, mix with oily materials, add water to form a cream, easily washed off skin
- Water in oil- wool fat, wool alcohol, beeswax, increase water holding capacity of greasy bases
Other
Water in oil emulsions: calcium soaps
Oil in water emulsions: soft soap
Water in oil emulsions: synthetic low HLB
Oil in water emulsion: synthetic high HLB
What are suspending agents used for?
For suspending solids in a lotion or to produce gels
What are clays (suspending agent)?
- bentonite
- leave a lubricant layer of powder on skin
What are gelling agents? (suspending agent)
- give a range of consistency
- tragacanth, methylcellulose, alginates for aqueous gels, cetostearyl alcohol and beeswax for oils
What are wetting agents?
For hydrophobic solids
Eg. Tinct of quillaia
What are humectants?
Reduce the rate of water loss from a cream and gel
Eg. propylene glycol, glycerol, sorbitol, syrup
What are solids for?
- added to semi-solic occlusive bases to reduce occlusiveness
Eg. Zinc oxide, talc, starch
What does dusting powders mean?
- Mix in motal with pestle using doubling up technique
- may need to sieve
What are liquid preparations used to make?
Solutions, suspensions and emulsions
What are ways of semi-solid preparation?
- Mixing by fusion
2. Mixing by trituration
Describe Mixing by fusion and how it is done
- Many oily materials are solid at room temperature (waxes)
- Mix by melting ingredients in evaporating dish in water bath (60-70 degrees)
- Waxy solids grated first and melted first
- When melted, remove heat, stir gently to avoid air bubbles until cold
- Medicament added at different stages according to solubility and stability
- Recovery of all the product may not be possible (prep 10% excess)
What are ointments?
Semi-solid preparations which may contain a medicament or mixture of medicaments dissolved or dispersed in a suitable greasy base
Used as:
- Emollients
- Protective preparations on the skin
- Local application of medicaments
What kind of creams are there?
- Aqueous cream: water miscible
- > effectively deliver medicaments to body surface - Oily creams: oil miscible
- > protective and emollient cream - Surface active agents: Cationic (+ve), anionic (-ve) and non ionic
What are the steps of compounding creams by fusion?
- Water bath- heat waxes and oils separately to the water and dissolve watersoluble ingredients (60-70 degrees)
- Insoluble ingredients: incorporate on glass slab by trituration
- Grate waxes if necessary. Add oils last
- Add water to oil at same temperature
- Cool slowly with stirring to avoid lumps
What are the features of aqueous cream?
Light emollient used to soothe, smooth and hydrate the skin and are indicated for all dry or scaling disorders
- need to be applied frequently
- aq cream can be used as a soap substitute
What does menthol do in cream?
- soothes and cools skin
- dilates blood vessels, causing a sensation of coldness followed by an analgesic effect
- > relieves itching and is used in creams, lotions, or ointments in pruritus and urticaria