internal and external emulsions Flashcards
what is the size of a microemulsion?
less than 1 micrometer
what will the type of emulsion depend on?
properties of the drug and the use of the product
uses of injections:
oral emulsions, IV/IM injections, total parenteral nutrition, creams / lotions
Factors to consider
Choice of emulsion - o/ or w/o
choice of oil phase - internal vs external
conc of the dispersed phase - maximum 60%
particle size of the dispersed phase
viscosity vs density of the continous phase
what type of emulsion is an oral emulsion?
oil in water. active ingredient is oil
features of an oil in water emulsion
less greasy, can be less viscousm rapid absorption/evaporation on the skin. E.g. Derbac M
Features of a water in oil emulsions
greasy by nature, more viscous and occlusive, most commonly use liquid paraffin
What are the features of an ideal emulsion?
Globule of the dispersed phase retain their initial character, stay the same size and remains evenly dispersed
problems with emulsion?
Cracking: water come out of the dispersed phase and cannot be redispersed.
creaming; oil rises to top or sinks to the bottom in an o/w emulsion, shaking can redisperse
why are oil in water emulsions given instead of just oil?
to make it more platable
what do emulsifying agents do?
prevent droplets from coalescing
what are the 3 types of emulsifying agents?
Natural and synthetic emulsifying agents, synthetic, finely divided solids
Features of a natural emulsifying agent?
they are less stable than others.
- polysaccharides (internal o/w)
- semi synthetic polysaccharides (o/w)
- sterols (external /o)
give examples of a natural emulsifying agent polysaccharides
acacia, starch, pectin, tragacanth
give examples of a natural emulsifying agent semi synthetic polysaccharide
methylcellulose
give examples of a natural emulsifying agent sterol
beeswax, wool fat
what will determine your choice of emulsifying agent?
type of emulsion, route of adminstration and active ingredient
what do antioxidants do?
they are added to the oil phase as oils are liable to oxidation
what do preservatives do?
they protect the water phase from microbe growth
examples of preservatives
benzoic acid, chloroform, cetrimide, chlorocresol
excepients in an emulsion?
antioxidants, preservatives, colours and flavours, emulsifying agents
How can creaming and cracking be prevented?
Retaining globule size at optimum size
Stopping extremes of temperature
Using stabilisers to prevent coalescence
Preventing microbial contamination
what is the usual packagaing for oral / external liquid emulsions?
glass/plastic bottle
advantages of internal emulsions?
makes oils palatable for use. -easy to swallow -fast absorption from GIT Enables oils to be given IV Depot injections can improve compliance
disadvantages of internal emulsions?
not stable, can crack and cream, difficult to manufacture, can b inconvenient for patient, must shake before use, storage is important
advantages of external emulsions?
cooling effect on skin, local effect, no systemic side effect, can be greasy/non greasy
disadvantages of external emulsions
unstable, difficult to pay, must shake bottlem paraffin can be flammable, preservatives can irritate skin
what do collodions do?
they form a water proof film on the skin
are collodions flammable?
yes, highly
how are collodions packaged?
aluminum/plastic tubes or glass bottles
what does camphor?
makes the film water proof
what is a plasticiser and give an example
makes the film flexible & caster oil
what are some of the things you need to check in a final check of an emulsion?
creaming, cracking or phase inversion
- smell - chloroform not dissolved
- correct final volume
- clean bottle with label
