Internal and external emulsions Flashcards
Are oral emulsions o/w or w/o
Always o/w
Which is more greasy and more viscous, o/w emulsions or w/o?
w/o
In an ideal emulsion, globules of the dispersed phase retain their size and remain evenly dispersed. True or false?
True
Is cracking reversible?
No
Is creaming reversible?
Yes by shaking
What do emulsifying agents do?
Prevent droplets from coalescing
What are the three types of emulsifying agent?
Natural
Synthetic surfactants
Finely divided solids
Natural emulsifying agents are more stable than other. True or false?
False
Which type of emulsions are polysaccharides used in?
o/w internal emulsions
What type of emulsions are sterols used in?
w/o
What type of emulsions are semi-synthetic polysaccharides used in?
o/w
Non-ionic surfactants are used in all types of emulsions. True or false?
True
If an emulsifying agent has a high HLB, which type of emulsion is it suitable for?
o/w
If an emulsifying agent has a low HLB, which type of emulsion is it suitable for?
w/o
What is the choice of type of emulsifying agent dependent on?
The type of emulsion
The route of administration
Active ingredient
Oils are liable to oxidation. True or false?
True
What are antioxidants used for in emulsions?
To prevent oxidation of oils - they are added to the oil phase
Why are preservatives needed in emulsions?
Needed to prevent microbial growth in water phase as microbes may feed on emulsifying agent
Colours and flavours are not needed in emulsions. True or false?
False
What are the advantages of internal emulsions?
Makes oils palatable for oral use
Easy to swallow
Fast absorption from GIT
Enables oils to be given IV
What are the disadvantages of internal emulsions?
Not very stable Problems with cracking and creaming Difficult to manufacture Can be inconvenient for the patient Must shake before use Compliance with storage is important
What are the advantages of external emulsions?
Can have a cooling effect on the skin Local effect No systemic side effects Good for hairy areas Can often be used as soaps
What are the disadvantages of external suspensions?
Stability problems
Difficult to apply
Paraffin can be flammable
Preservatives can irritate the skin
What do colloidons do?
Form a waterproof film on the skin
When making emulsions extemporaneously, always make the primary emulsion with all the oil to ensure stability and then dilute with continuous phase to volume required. True or false?
True
