Skin function and preparations Flashcards
Anatomy Dermis
Connective tissue that supports epidermis.
Thickest layer.
Contains: collagen, elastin, immune cells, blood vessels, nerves, lymphatics, and sweat glands.
Hair follicles and sebaceous glands (alopecia and acne)
Epidermis anatomy
Thin layer of stratified squamous epithelial cells with 4 or 5 layers
Stratum corneum: outer layer and barier to environment - dead skin cells (result of keratinisation)
Contains: melanocytes (produce/store melanin), lymphocytes and langerhans cells (fight germs), mekel cells (connect to nerve endings- sense of touch)
Types of topical vehicles
Creams, ointments, lotions, gels, pastes, paints, powders, and sprays.
Pros/cons of cream
Pros: easy to spread, not as greasy as ointments, moistening and emollient properties
Cons: evaporate or absorb when rubbed in= less hydrating than ointments
Describe creams
Viscous semi-solid preparations, usually emulsions
May be:
- water miscible (oil-in-water emulsions) - aqueous creams
- oil miscible (water-in-oil emulsions) - oily creams
Used to apply active ingredients for protection, therapy, or prophylaxis.
Usually opaque
Applied to flexures, genital, large areas. Suitable for dry and weepy skin conditions.
Hypodermis (subcutaneous layer) anatomy
Thermal control and energy storage
Contains: adipose and connective tissue, blood vessels, and nerves
Varied thickness
Skin function - primary
Primary function- protective barrier to environment
- prevent loss of bodily fluids, prevent entry of foreign bodies, contain body structures and organs
Skin pH
Aprrox 4.5-5.5 (acid mantle)
Due to fatty acids, amino acids, lactic acids, resident microflora (protection).
Other skin functions
Regulate temperature
Vitamin D synthesis
Protect UV, sense
Blood reservoir
Excrete unwanted substances in sweat
Influencing factors on skin
Age
Immunological status
Underlying disease status
Medication - isoretinoin/drying
Describe ointments
Semi-solid preparations, solutions or dispersions
Hydrophillic greasy base (white soft paraffin) to form occlusive layer (prevent loss of heat and water)
Greasy= limi patient compliance, not appealing
Enhance absorption of some drugs - improved contact time w/ skin
Apply to areas free of hair (palms and soles) or short hair, dry skin.
Pros/cons of ointments
Pros: Increase hydration and temperature of skin, do not contain preservatives
Cons: greasy, difficult to wash off, not easily spread
Describe lotions
Liquid or semi-liquid preparation
Opaque, thin, and non-greasy
May have aqueous, ethanolic, or emulsified vehicles w/ antiseptic, analgesic, soothing, or protective properties
Produce cooling effect from evaporation of water from skin, may dry out to form a film
Apply on intact skin only, oral mucosa, hairy areas (scalp, armpits)
Pros/cons of lotions
Pros: cooling effect, easily applied on hairy areas, spread easily and rapidly
Cons: less hydrating than ointments and creams
Describe gels
Transparent or transulent semi-solid preparations
Apply to skin and mucous membranes
Liquid phase suspended in 3D polymer matrix (drug dissolved in matrix)
Produce cooling effect from evaporation of water -may dry out to form residual film
Gels pros/cons
Pros: cosmetic elegance, easy to apply and wash off, cooling, non-greasy
Cons: no occlusive, little hydration, perspiration can remove
Describe pastes
Semi-solid preparations w/ protective properties that may be used for delivery of active ingredient
Fine powder w/ soft paraffin or w/ non-greasy base consisting of glycerol, mucilages, soaps, emulsifying waxes and ointments
Apply to thick skin or mucous membranes
Pastes pros/cons
Pros: drying and protective, more occlusive and absorptive, less greasy
Cons: Difficult to spread (enhance contact time to area)
Describe powder
Solid preparations mixtures w/ 2+ powdered active ingredients
Starch, talc, or kaolin
Apply to broken/unbroken skin on most body areas
Powders pros/cons
Pros: absorb moisture, easy to spread and apply
Cons: overuse can cause powdery residue
Describe sprays
Formulated in suspension aerosols
Normally contain a lubricant or dispersing agent
Capable of treating large areas
Apply to direct area that is fainful
Sprays pros/cons
Pros: application w/out touching skin, have a cooling effect, little waste
Cons: cause stinging and burning on application
Factors influencing treatment of skin conditions
Skin damage (burns/eczema) increases permeability
Skin damage (psoriasis) reduces permeability
Permeability varies at different lipid structures (facial is more permeable), skin folds are more, palms and soles resistant
Skin hydration increased from humidity, occlusion, or dressings - increase systemic drug absorption
Children have a higher surface area (weight ratio absorbs higher systemic dose) - preterm neonates have less effective stratum corneum
Old people w/ thin/fragile skin have increased skin permeability
Emollients vs moisturisers
Emollients - soften (prevent water loss)
Both have lipids (replace natural oils)
High lipid, low water = heavy, greasy
Moisturiser ingredients
Humectants - add water to stratum corneum
Emollients - soften and prevent water loss
Occlusives - form physical barrier to prevent water loss
