Topical medicines Flashcards
What does the skin protect against?
Pollution, Temperature, humidity, radiation
What are the functions of the skin?
-protection for internal organs
-limiter for the passage of chemicals
-stabaliser for blood pressure and temperature
-expresses the emotions of fear,anger embarassment, anxiety
-indiciation of human characteristics such as colour, hair, odour, texture
Is skin easily damaged?
Yes
What physical damage can affect skin?
cuts, bruises, burns, radiation exposure
what chemical damage can affect skin?
bites, stings, detergents, chmeical residues, solvents, pollutants
What biological damage can affect skin?
microorganisms (bacteria, fungi, viruses)
what are the three main regions of the skin?
Epidermus - top layer
dermis - middle layer
subcutaneousn tissue - bottom layer
Epidermus characteristics
-Multilayered and varies in thickness - palms and soles are thicker than eye lids
- stratum corneum is the dead, dense and almost impremeable surface layer
-swells severel-fold in water (maceration) like sopggy fingures in shower
Dermis characteristics
-3-5mm thick
-matrix of connective tissue voven from fibrous proteins (collagen, elastin, reticulin)
- nerves, blood vessels and lymphatics traverse the matrix and skin appendages pierce it
Subcutaneous tissue characteristics
- subcutaneous fat (subcutis, hypoderm) provides a mechanical cushion and a thermal barrier
-synthesises and stores readily available chemicals
What are the four skin appendages?
Eccrine sweat glands
Apocrine sweat glands
sebacious glands
hair folicles
Eccrine sweat gland characteristics
-produce sweat of pH 4.0-6.8
-secreate drugs, proteins, antibodies and antigens
-aid heat control
Apocrine sweat glands characteristics
-develop at the pilosebacious follicle
-milky or oily secreation contains proteins, lipids, lipoproteins and saccharides
-surface bacteria metabolise this initially odourless liquid to produce body smells
Sebacious glands characterisitics
-sebacious glands open into hair follicles
-they produce sebum from cell disintegration
Hair follicles characterisitics
-develop over all skin except lips, palms, soles
Basic structure of skin- draw and compare to template.
3 main approaches to drug delivery
(1) Manipulate the barrier function of the stratum corneum
-antibacterials/antibiotics help a damaged barrier to ward off skin infections
- sunscreens and the horny layer protect the viable tissues from uv raadiation
-emolients restore pliability to desiccated horny layer
(2) direct drugs to the viable skin tissues without using oral, synthetic, or other routes of application
(3) skin delivery for systematic treatment
-transdermal therapeutic systems provide systematic therapy for a variety of conditions
eg. motion sickness, angina, smoking cessation, hormonal drug therapy
Treatment of the stratum corneum
-To hydrate the horny layer (to treat dry or scaling disorders or to remove dead skin cells from the surface of skin)
-to simulate cloughing (keratosis) or exfoliation
Emolient characterisitics
-sooth, smooth and hydrate skin
-indicated for all dry or scaling disorders
-as the effects are short-lived, they are applied frequently
-useful in dry and eczematous disorders
-have limited use in treatment of psoriasis
-mostly lotions, creams or emulsions
Comercially available emolients
Non propietary - aqueous cream BP, white soft paraffin BP, Liquid and white soft paraffin ointment BP
Propietary - neutrogena, cetroben, ultrabase
Treatment of skin appendages
-Reduce hyperhydrodsis (excess sweating) of the sweat glands
eg. with antiperspirants containing aluminium salts (anhydrol forte)
-treatment of mild-modearte acne
eg. topical exfolients such as salycilic acid, benzoyl peroxide
topical antibiotics containing erythromycin and clindomycin
-Treatment of fungal diseases (localised)
eg. dermatophytoses of the scalp, body, groin, hand, foot or nail
topical imidazoles include clotrimazole, econazole, miconazole, keraconazole
-Treatment of mail pattern baldness
eg. finasteride, minoxidil
Treatment of the viable epidermis / dermis
-efficient delivery of drug to the receptor
-use of pro-drugs (release acrive ingridient when at target receptor)
-Anti-inflammatories: steroidal and non steroidal NSAIDs
non-propietery: ketoprofen gen, piroxicam gel
propietery: oruvail gel, feldene gel, voltarol,fenbid
-Anaesthetics: releif of local pain (can cause hypersensitivity)
-benzocaine, amethocaine, lingocain
-Antipuritics: alleviate itching of puritis in eczema
-Calamine, Eurax, Xepin
Antihistamines: effective against insect bites and stings (not eczema)
-anthisan, wasp-eze
UV (PUVA) and Light (PDT) therapies: The psoralens/with uv light might mitigate psolarisis
-aminoleavulinic acid/ with light treats skin cancer
Formulation - liquid preperations (1)
-simple soaks/baths
-an active ingrident in aqeous solution or suspension
-gums and gelling agents may very the consistency (visocity enhancer)
-oilatum emolient math additive deposits a layer of liquid parafifin/wool alcohols on stratum corneum
-oilatum plus contains benzalkonium chloride and triclosan as parasiticides/antiseptics
Liquid preperations (2)
Liminents
-alcohol or oily solutions or emultions
-do not apply to broken skin
-massaged into the skin as counterirritants
-can contain methyl salicylate or camphor
Lotions
-aqeous solutions/suspensions
-evaporation of water/alcohol cools and sothes the skin
-can be dilute oil/water emulsions
Formulation - ointments
Greasy, smisolid preperations
-hydrocarbon bases (vasoline)
- fats and fixed oil bases
-silicone bases
-absorption bases
-emulsifying bases
-water-soluble bases
Formulation - creams
Oily creams
-contain a w/o emulsifying agent
-wool fat, wool fat alcohols, fatty acid sobitan esters and their salts (eg calcium)
Aqeous creams
-contain an o/w emulsifying agent
-emulsifying waxes/alkali salts of fatty acids
-polyethylene glycol derivatives of sorbitan esters (tweens)
example of solid/semisolid formulation (1)
Zinc and salicylic acid paste BP (lassar’s paste)
-non-propietery paste for the treatment of hyperkeratotic skin disorders, warts and calluses, scalp conditions and fungal nail infections
zinc oxide - mild astringent and topical protectant with some antiseptic action
salicylic acid - exfolient
starch - binder and thicking agent
white soft parafin - emolient
example of solid/semisolid formulation (2)
Emulsifying ointment BP
-mixture of emulsifying wax - cetostearyl alcohol/sodium lauryl sulphate, white soft paraffin, liquid paraffin
-readily miscible in water and forms a n emulsifying base for many topical preperations, on its own, indicated for all dry and scaling disorders
cetostearyl alcohol - emolient/emulsifyer/visocity enhancer
sodium lauryl sulphate - anionic surfactant/ wetting agent skin penetrant/emulsifying agent
White soft paraffin - emolient
liquid paraffin: emolient
