Pharmacology Flashcards
what are the three major routes of drug administration in the skin?
topical
transdermal
subcutaneous
what effect do topical treatments have?
local
what effect to transdermal and subcutaneous treatments have?
systemic
what is the most important barrier to drug penetration in the skin?
the stratum corneum (keratin layer)
what are the two routes of drug diffusion across the stratum corneum?
intercellular
transcellular
what is the equation to determine the rate of absorption of a topical drug?
J= Kp x Cv
Kp = permeability coefficient
Cv =concentration of drug in vehicle
does a lipophilic drug in a lipophilic vehicle absorb well?
ish
does a lipophilic drug in a hydrophilic vehicle absorb well?
yes
does a hydrophilic drug in a lipophilic vehicle absorb well?
kinda - weak
does a hydrophilic drug in a hydrophilic vehicle absorb well?
nope
stays on the skin
what can enhance the solubility and absorption of a topical drug?
excipients
name an excipient that can. be added to topical drugs
propylene glycol
how well absorbed are topically applied drugs?
poorly absorbed
only a small amount moves into the skin
name two things that can increase how much of a topical drug partitions into the skin
hydration of the skin by occlusion i.e. appropriate vehicle or wrapping the area in cling film
inclusion of excipients to increase solubility
what causes increased partitioning of topical drugs?
reduction in the barrie function of the stratum corneum
name three conditions that topical glucocorticoids are often used to manage
atopic eczema
psoriasis
pruritus
what are the four categories of topical glucocorticoids?
mild
moderate
potent
very potent
name three formulations that topical glucocorticoids can be administered in
lotions
creams
ointments
what causes steroid rebound due to topical glucocorticoid use?
glucocorticoid receptor down regulation
name a possible systemic effect of topical glucocorticoids
HPA axis depression
what skin changes can be caused by topical glucocorticoids?
skin atrophy
steroid rosacea
stretch marks
telangiectasia
what is the proper term for stretch marks?
striae atrophica
are glucocorticoids lipophillic or lipophobic
lipophillic
how do glucocorticoids enter cells?
via diffusion across the plasma membrane
describe the subcutaneous route of drug administration
drug is delivered by a needle inserted into adipose tissue directly underneath the skin - the subcutaneous tissue
what effect does topical administration have on drug metabolism?
allows drugs to avoid first pass metabolism
how can transdermal drug delivery be achieved?
drug incorporated into an adhesive patch that is applied to the epidermis
describe the properties of a drug that would be suitable for administration via the transdermal route
low molecular weight
moderately lipophillic
potent
relatively brief half life
name some drugs that can be administered via the transdermal route
scopolamine nicotine GTN fentanyl buprenorphine oestradiol
