Pharmacology Flashcards
what is a major advantage of topical drug administration
high drug concentration at intended area with low systemic effects
describe the brick and mortar model of the skin
corneocytes surrounded by intercellular lipids (cholesterol, ceramides, free fatty acids)
what is the most important barrier against drug absorption in the skin
stratum corneum (corneocytes and lipids)
what are corneocytes
hardened dead keratinocytes
are the intercellular lipids hydrophobic or phillic, what does this mean
hydrophobic, can serve as a reservoir for hydrophobic, lipid soluble drugs drugs
are most drugs permeable to the skin hydrophobic or phillic
phobic
what are the dissadvantages of topical treatments
time consuming, difficult to get correct dosage, messy
what are the bases and vehicles and what are the purposes
to give different concentrations and theraputic uses
gels creams ointments pastes lotions foams
what is a cream and what does it contain
semisolid emulsion of oil in water, contains emulsifier and persevatives. high water content
what are the benefits of creams
cool and moisturising, non greasy, easy to apply, cosmetically acceptable
what are the disadvantages of cream
may smell unpleasant, allergies to preservants
what are ointments and what do they contain
semisolid grease/oil (soft parafin), no preservative
what is pruritus
itch
what influences the choice of vehicle for a drug
physiochemical properties of the drug, clinical condition of the skin, patients preference (not oil on hair etc)
what can the vehicle affect
rate and extent of absorption
how can you maximise the partitioning (movement) of a drug into the skin
disolve it in a base that promotes absorption
a lipophilic drug in a lipophilic base is soluble in both the vehicle and the skin and partitions between the two
a lipophilic drug in a hydrophilic base is more soluble in the skin and partitions readily and preferentially into it
a hydrophilic drug in a lipophilic base has limited solubility in both the vehicle and the skin and partitions into it to a limited extent
a hydrophilic drug in a hydrophilic base is soluble in the vehicle but not the skin and remains on the surface of it
what type of process is transdermal drug delievery usually
passive driven by diffusion
what law describes the rate of absorption
ficks law
J (flux) (rate of absoprtion) = Kp (permability coefficient) x Cv (conc of drug in vehicle)
what provides the driving force of absorption in topical drugs
only fraction of drug that is dissolved in the vehicle
what happens to undissolved drug in the vehicle- why is this important
dissolves when conc of dissolved drug goes down- helps maintain steady rate of delivery and increases lifetime of the drug
inclusion of what in the vehicle can enhance solubility and absorption
excipients
what physical and chemical factors can improve partitioning
hydrating the skin by occulsion (prevents water loss)
inclusion of excipients which increase the solubility of hydrophobic drugs
increased partitioning results from what happening in the skin
reduction of statum corneum barrier function
what vehicle should be used if skin is dry
lotion
what vehicle should be used if skin is weeping/moist
powder
what are three conditions treated by glucocorticoidsteroids
atopic eczema, psoriasis, pruritus
what are the clinical effects of glucocorticoid steroids
anti-inflammatory, immunosupressant, vasoconstricting, anti proliferating action upon keratinocytes and fibroblasts
what affects glucocorticosteroid penetration, potency and clinical effect
body site, state of skin, occulsion, vehicle, concentration of drug, form of drug
what are the serious side effects of potent long term steroids
steroid rebound, skin atrophy, systemic effects (HPA axis depression, adrenal suppresion, cushings syndrome), spread of infection (immunosuppressed), stretch marks and pupura, tachyphylaxis
if topical- steroid rosacea, fixed telangectasia, perioral dermatitis (inflammatory skin conditions)
if near eye; glaucoma, cataract
describe glucocorticoid molecules and their receptors
lipophillic molecules that diffuse across plasma membrane to bind the nuclear receptors (esp. GRalpa) which then bind to glucocorticoid response elements
what is the subcutaneous route of administration
injected into fatty adipose tissue
how do drugs administered subcutaneously reach the systemic circulation
diffuse into capillaries or lymphatic vessels
what are the advantages of subcutaneous administration
absorbed slowly due to poor vascularisation, suitable for oil and protein based drugs, can create a ‘depot’ of drug that is slowly absorped, simple and relatively painless
what is the disadvantage of subcutaneous
injection volume limited
how is transdermal drug delivery usually done
drug is incorportated into an adhesive patch and applied to the epidermis
what drugs are most suitable for transdermal
low molecular weight, moderately lipophillic, potent, relatively brief half life
name three agents that enhance trnsdermal drug delivery
water, solvents (ethanol), surfactants
how can you physically enhance transdermal drug delivery
iontophoresis- prolonged application of low voltage electrical pulses to the skin
electroporation- brief high voltage pulses
sonophoresis- ultrasound
microneedles
what are the benefits of an ointment
occlusive and emollient, restict transepidermal water loss
what are the negatives ointments
greasy, less cosmetically attractive, highly flammable
what are the components and characteristics of lotions
liquid formulation, suspension or solution of medication in water, alcohol or other liquids
what are a pro and con of lotions
pro- treat scalp, hair bearing areas as less greasy
con- if contain alcohol may sting
describe the constitutions of gels
thickened aqueous lotions, semi solid, containing high molecular weight polymers
what areas are gels best at treating
scalp, hair bearing areas, face
describe the constitution of pastes
semisolids, containing finely powdered material, stiff
what are the pros and cons of pastes
pros- protective, occlusive, hydrating
cons- greasy, difficult to apple
what are pastes often used for
cooling, drying, soothing bandages- prevent surrounding skin becoming boggy and macerated
describe the constitution of foams
colloid with two-three phases
usually hydrophilic liquid in continuous phase with foaming agent dispersed in gaseous phase
what are the advantages of foams
increased penetration of active agents, spread easily over large areas, non greasy/ oily skin
what do emollients do
enhance rehydration of epidermis for all dry/scaly conditions
for a full body application of emollients how much is needed per week
300-500g
what are the tips you need to give when prescribing emollients
- apply immediately after bathing
- apply in direction of hair growth
- make skin and surfaces slippery
- use clean spoon or spatula to remove from tub (risk of contamination)
- fire risk if paraffin based
- avoid SLS in leave on products
why does the price of emollients affect compliance
non proprietary emollient cheap but based on liquid parafin/white soft paraffin and less cosmetically acceptable
what is wet wrap therapy used for
very dry (xerotic skin), esp in children, stop itching
what is the basic three modes of action of topical steroids
vasoconstrictive
anti-inflammatory
anti-proliferative
what is the role of topical steroids
reduce inflammation, cause immune suppression
list topical steroids in order of increasing potency
hydrocortisone (1%)
modrasone clobetasone butyrate (0.05%)
mometasone betamethasone valerate (0.1%)
clobetasol proprionate 0.05%)
what are topical corticosteroids used to treat
eczema (dermatitis),
psoriasis (esp on face, hairline, scalp- beware rebound, triggering pustular psoriasis),
non inflammatory dermatoses (e.g. lichen planus)
keloid scars
what psoriasis condition is a medical emergency
pustular psoriasis
how much topical steroid is needed for a whole body application for an adult
20-30g ointment
how much is a fingertip unit
1/2g (covers two hand areas)
what do calicneurin inhibitors do
suppress lymphocyte activation (non steroidal anti inflammatory)
what are calicneurin inhibitors used to treat
topical treatment of atopic eczema (especially on the face or for children)
what are the pros and cons of calicneurin inhibitors
pros- less side effects than steroids, no cutaneous atrophy, one preparation can treat whole body regardless of site of application
cons- may cause burning sensation on application, possible risk of cutaneous infections and skin cancer (tell patient to wear suncream)
name two calicneurin inhibitors
tacrolimus, pimecrolimus
what should antiseptics be used as an alternative as
antibiotics to reduce resistance
name 4 antispetics
povidone iodine (skin cleanser),
chlorhexidine (hibitane, savlon),
triclosan (aquasept, sterzac),
hydrogen peroxide (crystacide)
what are the clinical uses of antiseptics
recurrent infections, antibiotic resistance, wound irrigation
name the method of administration of antivirals used to treat;
herpes simplex (cold sore)
eczema herpeticum
herpes zoster (shingles)
HS topical
EH and HZ oral
name the topical antifungals used to treat candida (thrush) (satellite lesions)
antiyeast e.g. nystatin, clotrimazole
name the topical antifungals used to treat dermatophytes (ringworm)
antifungal e.g. clotrimazole, terbinafine cream
name the topical antifungals used to treat pityriasis versicolor
ketoconazole
what is tinea corporis
ringworm
what is pityriasis versicolor
fungal infection causing pink inflammatory areas on the trunk or areas of hyperpigmentation
name four antipruritics and describe them
menthol- to cool skin (added to calamine)
capsaicin (reduce neurotransmission)
camphor/phenol- for pruritus ani
crotamiton- used after treatment of scabies to relieve residual itch
what do keratolytics do and treat
soften keratin
viral warts, hyperkeratotic eczema and psoriasis, corns and calluses, remove keratin plaques in scalp
what are the possible treatments of warts
keratolytics (e.g. salicyclic acid) formaldehyde glutaraldehyde silver nitrate cryotherapy podophyllin
name the possible topical treatments of psoriasis
coal tar vitamin D analogue keratolytic topical steroid dithranol phototherapy (guttate psoriasis)
what are the treatments used for stable chronic plaque psoriasis
coal tar,
vitamin D analogues,
dithranol
what are the pros and cons of coal tar
can be mild or strong
messy and smelly
what are the pros and cons of vitamin D analogues
pros; clean, no smell, easy to apply
cons; can be irritant, use limited to 100g weekly
what are the pros and cons of dithranol
pros; effective
cons; difficult to use, irritates and stains normal skin surrounding plaque
what is the treatments for scalp psoriasis
greasy ointments to soften and remove scale then
tar shampoo
steroids in alcohol base or shampoo
vitamin D analogues
what treatments are used for psoriasis in axialla
topical steroids for face, flexures and groin/genitals
consider combination antibacterial, antifungal,
calcineurin inhibitors
what are the side effects of topical therapies used for psoriasis
burning or irritation
contact allergic dermatitis
local toxicity
systemic toxicity
reaction to sunscreen
what is a side effect of 5- fluorouracil
inflammation
name two systemic side effects of topical steroids
suppression of HPA acis by increasing negative feedback
cushings disease
growth retardation
what are 6 reversible steroid side effects
contact allergy to hydrocortisone
acneiform eruptions (peri-oral dermatitis, steroid follicultitis, steroid rosacea)
tachyphylaxis (decrease in response to drug)
pigment changes
poor wound healing
modification to existing disease (fungal, scabies, rosacea, rebound of pustula psoriasis)
what are the permanent cutaneous side effects of steroids
striae (stretch marks) atrophy, bruising, telangiectasia (dilated superficial blood vessels) glaucoma, cataract hirutism poor wound healing
thinning of skin is more likely in children
yes
