Semi-solid preparations Flashcards
What are semi solid preparations used for?
Inflammation Pain Itching Protection Lubrication Emollient
What are the 4 types of semi solids?
Ointments
Creams
Pastes
Gels
Can semi-solids be used for systemic action?
Yes - e.g. Percutol ointment
Ointments are highly occlusive therefore good for oily skin. True or false?
False - good for dry skin
Do ointments have hydrous or anhydrous vehicles?
Anhydrous
Creams are more occlusive than ointments therefore good for macerated skin. True or false?
False- less occlusive
Pastes form a thick _______ layer on skin.
impermeable
What are polymers e.g. carbomer for in gels?
To produce a matrix to allow the drug to diffuse through the gel to the site of action
Liquid paraffin, soft paraffin and paraffin wax are examples of _________ used in semi-solids
mineral oil vehicles
What are surfactants used for in semi-solid preparations?
To help oil and water form a stable uniform mix
Increase the penetration of the drug
Sorbitan laurate is an example of a _______ surfactant
non-ionic
Humectants such as ______ reduce loss of water from creams and gels
glycerol
Products high in water are usually most stable. True or false?
False - products low in water e.g. ointments and pastes
What affects the stability of semi-solids?
Heat
Light
Micro-organism growth
What are the advantages of ointments and pastes?
More stable than creams and gels
Occlusive and protective
Good for dry skin
Less need for preservative
What are the disadvantages of ointments and pastes?
Greasy and sticky
Slow absorption into skin
Not to be used on macerated skin
High oil content could lead to them being flammable
What are the advantages of creams and gels?
Non greasy
Rapid absorption into skin
Have cooling effect on evaporation
Can be used on macerated skin
What are disadvantages of creams and gels?
Susceptible to microbial contamination
Require preservatives which can cause sensitisation
Less stable
Short duration of action due to rapid absorption
Drugs in aerosols require _______
propellants
Why must you shake an aerosol?
To disperse the propellant and drug
What is the definition of trituration?
incorporating liquids or powders into a semi-solid using a ceramic tile
What does levigation mean?
Applying pressure to incorporate a powder into a semi-solid.
