Dermatology Flashcards
what type of drugs does the stratum corneum let though the epidermis
small, hydrophobic drugs
what is the function of a vehicle
maximises the movement of a drug across dermal layers
what is the most effective/soluble drug and vehicle combination
lipophilic drug in a lipophilic base
what is the least effective drug:vehicle combination
hydrophilic drug in a hydrophilic base (stays on surface of skin)
name 4 factors improving partitioning
- hydration of skin by occlusion (prevent water loss)
- inclusion of excipients - they increase the solubility of hydrophobic drugs
- site of application - where site of stratum corneum is thin
- integrity of epidermis - absorption increases in areas of trauma
give some advantages of subcutaneous delivery of drug
- slow absorption due to poor vascular supply
- can introduce a depot of drug under the skin - this can be slowly released into circulation
- avoids 1st pass metabolism
- allows for steady state plasma concentration
subcutaneous delivery is a good route of administration for which drugs
protein drugs - insulin
oil based drugs - steroids (cortisol)
transdermal delivery is most suitable for drugs with what characteristics
low molecular weight
moderatley lipophillic
potent
brief 1/2 life
Give 2 advantages of transdermal drug delivery
- steady state of drug delivery
2. its convenient, so increases patient compliance
is there many drugs suitable for trans dermal delivery tho
nah there’s not.
what is the main way to chemically enhance trans dermal drug delivery
use of enhancers - they increase the permeability of the stratum corneum
what is the main drawback of enhancers
they can cause irritation and are not effective for highly water soluble drugs
Give some examples of enhancers
water
solvents (ethanol) and surfactants
if used to treat psoriasis, what can topical steroids cause
they can cause rebound and then pustular psoriasis
