Dermal Formulations Flashcards
What are the properties of ointments? What are the bases?
semi-solid
- usually occlusive = retain moisture
- more oily than creams
may contain active ingredients for local delivery or for emollients and/or protective roles
hydrophobic
- water free, low polarity
emulsifying
- contain o/w emulsions, anhydrous
What are pastes? What are the bases?
semi-solid
- up to 60% w/w dry solids
do not dissolve in aqueous or organic systems used to absorb exudates - fluid filtered from circulatory system highly occlusive photo-protective - protects from light
bases can be
- hydrocarbons
- fats
- aqueous gel bases = less commonly used
What are creams?
semi-solid
- emulsions = more fluid than ointments or paste due to high water content (above 50%)
- external application
oil in water emulsions
What are the advantages of creams?
rapidly absorbed
leaves mo residues
lubricating yet pleasant feel
easily dispersed from containers
have greatest patient acceptability/compliance
What are the disadvantages of creams?
watery bases require preservatives to prevent microbial growth
may require pH buffer due to high water content
may need an anti-oxidant
formulation is more complex
What are waxes?
esters of an alcohol and carboxylic acid
- both have long alkyl chains
hydrophobic malleable solids of low melting points and low viscosities when liquefied
often are blended with true waxes
What are lotions?
external application to the skin
- should only be applied to intact skin
- excipients may cause damage to granulating tissues in wounds or systemic toxicity
have continuous aqueous phase
can be solutions, emulsions, suspensions
What are gels?
viscous semi-solid
- contain a gelling agent
usually aqueous
- can contain polar or non-polar solvents
thickening agent provides a scaffold to provide structure to the gel
gels can dry the skin
- especially if alcohol based
gels evaporate quickly
- leaves drug in contact with the epidermis
- evaporation of solvent can cause a cooling effect
What are powders?
solids
- rarely contain any potent drug substance
- may act as lubricants
adsorption is one of the most common purposes
- can adsorb sweat or other exudates
- talc, starch
highly inefficient delivery into the skin
powders are very simple, cheap, and stable medications