Pharmacology Flashcards
what are the main routes of drug administration in the skin?
topical
transdermal
subcutaemous
other epithelial routes (airways conjunctival sac, nasal mucosa and vagina)
model of the stratum corneum
brick and mortar model
three types of diffusion for drug delivery into the skin
intercellular
transcellular
transappendageal
which vehicle contains the most water
lotions
which vehicle contains the least water
powders
pastes
describe lotion
suspension/solution of medication in water
when can lotions sting?
if they contain alcohol
what are lotions used to treat?
hair bearing areas such as the scalp
describe creams
semisolid emulsion of oil in water, containing emulsifier and preservative
what is good about creams
they are non-greasy so cosmetically acceptable
describe ointments
semisolid grease that does no contain a preservatives
what is bad about ointments?
they are less cosmetically acceptable
describe gels
thickened aqueous solutions containing high molecules weight polymers e.g. methyl cellulose
define pastes
semisolids finely powdered material (ZNO)
stiff, greasy and used in bandages
describe foams
colloid with two or three phases
five types of topical therapies
- emollients
- topical steroids
- anti-infectives
- antipruritic
- keratolytic
when are emollients used?
dry/scaly conditions
appliance of emollients
300-500g per week
after bathing
in direction of hair growth
role of topical steroids
vasoconstriction and antiinflammation
range from mild to very potent
appliance of topical steroids
20-30g for whole body
side effects of steroids
thinning of skin purpura rosacea telangiectasia systemic absorption (Cushing's) tachyphylaxis
three types of anti-infectives
antiseptics
antivirals
antifungals
examples of antiseptics
iodine
hydrogen peroxide
triclosan
chlorhexidine
examples of antifungals
nystatin
clotrimazole
ketoconazole
examples of antipruritics
methanol
capsaicin
phenol
crotamiton
role of keratolytic therapies
soften keratin
when are keratolytics used
warts
role of calcineurin inhibitors
suppress lymphocyte activation
factors that increase partitioning into the skin
hydration of skin by occlusion
inclusion of excipients
role of excipients
increase solubility of hydrophobic drugs
factors that affect absorption
nature of the skin e.g. site, hydration and thickness
drug preparation e.g. concentration, sail and vehicle
define the subcutaneous route of administration
needle into adipose tissue
how does the drug delivered by subcutaneous route enter
enters systemic circulation via capillaries or lymphatic vessels
benefit of subcutaneous route of administration
slow absorption
disadvantage of subcutaneous route of administration
limited volume injected
why is the skin a beneficial route for drug administration?
simple and non sterile
allows for steady-state plasma concentration
avoids first pass metabolism
drug absorption can be terminated rapidly
disadvantage of the skin as a route for drug administration
only a limited number of drugs can diffuse across the epidermis
describe transdermal drug delivery
drug is incorporated into an adhesive patch
how does transdermal drug delivery increase permeability
enhancers interact with the lipid matrix
