Skin Anatomy, Function, Preparations Flashcards
What are the two main functions of the skin?
Protective barrier to environment
- Prevent fluid loss, entry of foreign body/chems
pH = 4.5-5.5 (acidic mantle)
- Acidity due to fatty/amino/lactic acids/microflora
What are some other functions of the skin?
reg temp
synth vit D
protect against UV damage
sensory
blood reservoir
Excretion of unwanted substances through sweat
What factors influence skin and its function/anatomy?
Age
immunological status
Underlying disease status
medications (e.g. isotretinoin and drying effect)
Outline the characteristics of creams
Viscous semi-solid opaque preparation = contains more additives/preservatives (more reaction risk)
Can be: aqueous cream (oil in water = water miscible) or oily cream (water in oil = oil miscible)
Apply active ingredients to skin = protective, therapeutic, or prophylactic
Where can creams be applied?
All areas of body = genitals, flexures, large areas
dry and weepy/exudative skin conditions
What are some advantages and disadvantages to creams?
Advantages = easy to spread, not as greasy, moistening, emollient properties
Disadvantages = mostly evaporates or absorbed once rubbed in –> less hydrating than ointment
Discuss the properties of ointments
Semi-solid preparations (solutions or dispersions) = hydrophilic greasy base –> form occlusive barrier
Can enhance absorption of some drugs
Where can ointments be applied?
areas free from hair (palms, soles)
Areas of short or spares hair
Dry skin of trunk and extremities
What are some advantages and disadvantages to ointments?
Advantage = Inc hydration and temperature of the skin, do not contain preservatives
Disadvantage = greasy texture, difficult to wash off, not easily spreadable
Discuss the properties of lotions
Liquid or semi-liquid preparations, opaque/thin/non-greasy
May contain aqueous/ ethanolic or emulsified vehicles (can dry out the skin due to alcohol content
Where can lotions be applied?
Moist surfaces including = oral mucosa, hair bearing areas (scalp, armpits)
Intact skin only
What are some advantages and disadvantages to lotions?
Advantage = provide cooling effect, easily applied to hair-bearing areas, spread easily/rapidly
Disadvantages = less hydrating, contain alcohol, can only be put on intact skin
Discuss the properties of gels
Transparent or translucent semi-solid preparations
Liquid phase suspended within 3D polymer matrix
Where can gels be applied?
Most areas of body
oily areas such as face
skin and mucous membranes
What are some advantages and disadvantages to gels?
Advantage = cosmetic elegance, easy to apply/wash off, provide cooling sensation, non greasy
Disadvantage = may dry skin out once water evaporates, no occlusive effects, little hydration, perspiration can remove gel
What are some characteristics of pastes?
semi-solid preparations w/ protective properties that may be used for the delivery of active ingredients
Finely powdered active ingredients combined with white paraffin or liquid paraffin, or non-greasy base (glycerol, soaps, emulsifying waxes, ointments)
Where can pastes be applied?
thick skin
Certain mucous membranes
What are some advantages and disadvantages to pastes?
Advantages = drying and protective, more occlusive and absorptive, less greasy than ointments, enhanced contact time to area
Disadvantages = difficult to spread
What are the properties of powders for skin conditions?
Solid preparations, mixtures of two or more powdered active ingredients (starch, talc, kaolin)
Where can powders be applied?
Moist body areas
Can be applied to broken and unbroken skin
What are some advantages and disadvantages to powders?
Advantages = absorbs moisture, easy to spread and apply, can be applied on unbroken skin
Disadvantages = overuse can cause powdery residues
Discuss the characteristics of sprays
Suspension aerosols
Contain lubricant or dispersing agent
Capable of treating large areas
Where can sprays be applied?
Where direct application is difficult or painful
What are the advantages and disadvantages to sprays?
Advantage = contact-less application, cooling effect, little waste
Disadvantage = can sting or burn
What factors influence topical treatment of skin conditions?
Skin damage = inc permeability
Crusting or scaling skin = reduce permeability
permeability = vary because of lipid structures of skin, skin thickness, potential occlusion
skin hydration = due to high humidity, occlusion, wet dressing –> inc systemic drug absorption
Children = higher surface area:weight ratio –> absorb higher systemic dose
Elderly = thin, fragile skin –> inc permeability
type of drug vehicle
What are some similarities between emollients and moisturisers?
Both contain lipids = emulsified oils and fatty acids (replace natural oils in skin)
high lipid, low water content = heavy, greasy
low lipid, high water content = lighter, less greasy
What ingredients do moisturisers contain that are different from emollients?
Humectants = add water to the stratum corneum
Emollients = soften and prevent water loss
Occlusives = form physical barrier to prevent water loss
When should moisturisers be applied?
After a bath = trap water in stratum corneum –> in direction of hair growth
Wait 30 mins before/after topical steroids to apply
How much moisturiser should be used?
liberally and regularly
Face = 15-30 g cream, 100mL lotion
Trunk (2wks) = 400g cream/500mL t
