Dermatologicals Flashcards
what are the 5 layers of the epidermis
stratum corneum stratum lucidum stratum granulosum stratum spinosum stratum germinativum
what are the layers of the skin
epidermis
dermis
subcutaneous tissue
what is the pH of the epidermis
acidic (pH=5.5)
role of the stratum corneum
major permeability barrier of the skin, controls percutaneous absorption
role of the stratum lucidum
responsible for skin stretch
role of the stratum granulosum
Site of biochemical activity (bioreactor)
role of the stratum spinosum
Change their morphology based on pressure placed on the skin
role of the stratum germinativum
□ Nucleated basal cells: dividing (mitosis) layer which replaces the shedding cells of stratum corneum
where are the nerves and blood vessels of the skin located?
dermis
what is the sink effect
Vascular supply: sink effect (dugs don’t accumulate in the skin–>the concentration gradient is always optimal
what is the function of the subcutaneous tissue
thermal barrier (Passive barrier doesn’t actually regulate heat: dermis blood vessels contract or expands based on heat) mechanical cushion
functions of the skin
elasticity
protective
what is an oleaginous base
○ Single phase–>ointments
Properties: Hydrophobic Greasy Non-water washable occlusive emollient
what does occlusion mean
formation of an impermeable layer on the skin to prevent evaporation of water
what does emollient mean
softens skin
advantages of oleaginous bases
Very stable vehicles
Non-irritating
Non-sensitizing
High compatibility with drugs (generally neutral)
disadvantages of oleaginous bases
Greasiness
Stains clothing
Difficult to remove
Low patient acceptance (
what are the liquids used to form oleaginous bases
fats and fixed oils Examples: almond, corn, cottonseed, olive, peanut, safflower, sesame seed, soybean oils
what are semisolids used to form oleaginous bases
Petrolatum and white petrolatum
what solids are used to form oleaginous bases
waxes
paraffin
do oleaginous bases need penetration enhancers
Yes
how do permeation enhancers work
fluidization of the stratum corneum lipids
do oleaginous bases require antimicrobials
No as they dont contain water
do oleaginous bases need levigating agents
yes when incorporating a powder into the ointment
they are less than 5% of the formula
mineral oil
or the base can be used
describe the process of fusion
melt the components together starting with the lowest melting point
then its is cooled with constant stirring until congealed
what are absorption bases
Non-water washable bases Hydrophobic Greasy Anhydrous; hydrophilic components provide water-absorbing properties Upon water addition form w/o emulsions Occlusive Emollient Used in oozing conditions
main components of absorption bases
Fats and fixed oils
Mineral oil
Petrolatum and white petrolatum
Waxes
other excipients of absorptive bases
All have water-absorbing capacity
Upon addition of water, form w/o emulsions
ex: lanolin, hydrous lanolin, cetyl alcohol, stearyl alcohol, stearic acid, oleic acid, glycerol monostearate, cholesterol
do absorptive bases need an antioxidant
Yes
BHA, BHT, alpha-tocopherol
do absorptive bases need penetration enhancers
determined on a case by case basis
do absorptive bases need antimicrobials
NO
use of levigating agents in absorptive bases
mineral oil
isopropyl myristate
glycerol, propylene glycol
absorption base can also be used
what is an emulsifying base
Water washable bases
Anhydrous bases containing o/w emulsifying agents
Cream-like appearance
Miscible with water
Self-emulsifying
Upon addition of water form o/w emulsions
Emollient
main components of emulsifying bases
Fats and fixed oils
Mineral oil
Petrolatum and white petrolatum
Waxes
are emulsifying agents needed in emulsifying bases
Yes, mostly hydrophilic emulsifying agents (SURFACTANTS)
are antimicrobials needed in emulsifying bases
NO
are antioxidants needed for emulsifying bases
YES
BHA, BHT, alpha-tocopherol
do penetration enhancers need to be used in emulsifying bases
on a case by case basis
when a levigating agent needs to be used for incorporating a solid into an emulsion base what are the options
less than 5% of the formula mineral oil isopropyl myristate glycerol, propylene glycol emulsifying base can also b used
for a dermatological emulsion what state is the oil phase
semi-solid
what are the characteristics of a w/o dermatological emulsion
Greasier than o/w emulsions (because oil phase is external)
Emollient, cleansing action
Capable of absorbing oil-soluble compounds from the skin (make-up remover)
what are the components of an w/o emulsion
Oil phase: all liquid, semisolid and solid excipients used for oleaginous bases: Fats and fixed oils, Mineral oil, Petrolatum and white petrolatum, Waxes
Emulsifying agents: Mostly surfactants
Water phase
what are the characteristics of a o/w dermatological emulsion
Water washable
Soft
Non-occlusive
Moisturizing (increases water content–>restores hydration of the skin)
Penetration enhancement of the drug compounds
are antioxidants used in emulsions?
Oil-soluble antioxidants: BHT,BHA, Alpha-tocopherol
Water-soluble: Ascorbic acid, Sodium bisulfate
do penetration enhancers need to be used in emulsions
evaluated on a case by case basis
Isopropyl myristate, oleic acid, oleyl alcohol
are preservatives required in emulsions
YES:essential
ex: alcohol, benzoic acid, phenols, methyl and propyl parabens
are humectants required for emulsions
Yes
propylene glycol, glycerol, PEG
is a levigating agent required to incorporate a solid into an emulsifying base
sometimes
use mineral oil, isopropyl myristate
can also use the water phase
what is a paste
Oleaginous bases with 20% or more solids suspended in the base
excipients of a paste
Hydrocarbon bases: all liquid, semisolid, and solid excipients used for oleaginous bases Fats and fixed oils Mineral oil Petrolatum and white petrolatum Waxes
is a paste water washable
NO, forms a thick impermeable layer on the skin as a protective action
is the use of a levigating agent appropriate
NO
what is a hydrophillic base
water washable base
Ointment like consistency (soften or melt on the skin)
Non-occlusive, mix with skin exudates
Doesn’t stain clothes (greaseless)
Non-irritant
Chemically stable: dont hydrolyze, deteriorate, don’t support mold growth
Cannot take up more than 8% water (loose consistency)
what are some incompatibilities with hydrophilic bases
Reduce the antimicrobial activity of quaternary ammonium compounds and parabens
Inactivate bacitracin and penicillin
what are the advantages of hydrophilic bases
Anhydrous–>useful for drugs that hydrolyze
Good patient compliance: non-staining, non-occlusive
what are examples of hydrophilic bases
Mixtures of low and high molecular weight polyethylene glycols (PEG):
MW 200-700–>liquid
MW 1000–>semi solid
MW>1000–>increasingly solid (flaky)
do hydrophillic bases require antioxidants
yes
water soluble antioxidants: ascorbic acid, sodium bisulfate
do hydrophilic bases require penetration enhancers
can use propylene glycol
do hydrophilic bases require humectants or preservatives
NO
what are gels
Water washable bases
Liquid-rich two-component semi-solid colloidal systems
Natural or synthetic polymers form a 3D matrix throughout a hydrophilic liquid
Properties: Dissolves in water, Good for hairy areas, Water-soluble drugs are easily incorporated either dissolved in the aqueous phase or dispersed in gel
do gels require antioxidants
ascorbic acid, sodium bisulfate
do gels require penetration enhancers
case by case
propylene glycol can be used
are preservatives required
can use the parabens
are humectants required in gels
YES: prevents product from drying out
ex: propylene glycol, glycerol, PEG
what is special about compounding gels
require time for hydration: sometimes takes up to 24 hours
what is a newtonian system
Flow in which viscosity is a constant value: it doesn’t change with the force applied to it
what is a non-newtonian system
Flow in which viscosity isnt a constant value–>viscosity changes with the force applied to it
what is plastic flow
Materials will not flow if the shear stress is below a certain value (liquid flows quite readily once the yield value is exceeded)
Ex: flocculated suspensions, ointments, creams, ketchup
what is pseudoplastic flow
Material shows decreasing viscosity with increasing shear rate=shear thinning
Solution at rest the interactions between molecules develops and chains become tangled
With stirring/shaking the interactions decrease and therefore viscosity
what is dilantant flow
Viscosity increases with increasing shear rate=shear thickening
By increasing shear rate the particles become displaced from their even distribution–>clumps form–>increased resistance to flow–>material appears paste like
what is thixotropy
Reversible time-dependent decrease in apparent viscosity–>gel-sol-gel
Viscosity is dependent on the length of time shear stress is applied
The structure of the liquid doesn’t reform immediately after altering its original flow properties
