Pharmacology Flashcards
What aare adjacent corneocytes held together by?
corneodesmosomes
What is conventional transdermal drug delivery driven by?
diffusion
What is Fick’s Law?
Rate of absorption (flux) is equal to the permeability coefficient times the concentration of drug
What are the important factors in the role of the vehicle?
The solubility of the drug in vehicle (Cy)
Maximising the movement of the drug from vehicle to the atratum corneum (drug must escape from vehicle)
What is the permeability coefficient (Km) described as?
the equilibrium solubility of the drug in the stratum corneum realtive to its solubility in the vehicle
What is the purpose of excipients?
They are put into the vehicle to enhance the solubitliy of the drug and so enhance absorption
Why might excess, non-dissolved drug be included into transdermal patches?
increases duration of effectiveness nad porvides a constant rate of delivery- dissolved drug that is removed by absorption is replaced by undissolved drug maintaining a fairly constant soluble concentration
Why are topically applied drugs generally poorly absorbed?
only a small fraction partitions into the stratum corneum
Name some factors that can improve partitioning
hydration of the skin by occlusion (increases the reservoir with which the drug can be absorbed)
inclusion of excipients which also increase the solubility of hydrophobic drugs
What are the factors that affect the absorption of topically applied drugs in drug preparation?
drug conc. the drug salt (different salts can have varying potencies) the vehicle (can affect how active a drug is)
What do glucocorticoids combine with in the cytoplasm?
GRalpha
What does combination of steroid with GRalpha cause the dissociation of?
inhibitory heat shock proteins
they were previously joined to GRalpha but steroid kicks it out
What does the steroid and GRalpha do in the nucleus?
bind to the glucocorticoid response elements which switches on or off transcription of specific
Where is subcutaneous drug delivered?
adipose tissue just beneath teh surface of the skin
How does subcutaneous drug reach systemic circulation?
diffuses into capillaries or lymphatics
What are some advantages to subcut drug administration?
absorption is relatively slow (poor vascular supply)
can be used to introduce a depot of drug under the skin that is very slowly released into the circulation
What is an advantage of subcut drug administration?
injection volume is limited
What is the skin a good route for a systemic effect?
avoids first pass metabolism
drug absorption can be terminated rapidly
What makes a drug suitable for transdermal drug delivery?
low molecular weight
moderately lipophilic
potenet
relatively brief half life
What is iontophoresis
application of low voltage electrical pulses to the skin via a surface electrode over a prolonged period of time can drive low molecular mass molecules (of the same charge) through the skin- move away from the same charge
What is electroporation?
very brief high volatge pulses lead to “pore” formation
What is sonophoresis?
use of ultrasound to increase skin permeability
What is a cream?
semisolid emulsion of oil in water
Creams contain both an emulsifier and a..
preservative
Due to their high water content, creams do what to the skin?
cool and moisturise
What is an ointment?
semisolid grease/oil (soft paraffin)
Do ointments contain preservative?
no
Why do ointments help to moisturise the skin?
occlusive- restrict transepidermal water loss
What is a lotion?
a liquid formulation- suspension or solution of medication in water, alcohol or other liquids
What areas are lotions used to treat?
scalp and other hair-bearing areas
What is a gel?
semi-solid, thickened aqueous lotions containing high molecular weight polymers
What areas are gels used to treat?
scalp, hair bearing areas, face
What are pastes?
semisolids, contain finely powdered material
What are the advantages of pastes?
protective, occlusive hydrating
What does an emollient do?
enhance rehydration of epidermis
What kind of conditions are emollients used for?
all dry/scaly conditions esp. eczema and psoriasis
What is wet wrap therapy used for?
very dry (xerotic) skin
What are the modes of action of corticosteroids?
vasoconstrictive
anti-inflam
antiproliferative
What are topical corticosteroids used for treating?
eczema
psoriasis
other non-infective inflammatory dermatoses- lichen planus
keloid scars
What are the skin side efects of topical steroids?
thinning of the skin; purpura; stretch marks; atrophy; steroid rosacea; perioral dermatitis; fixed telangiectasia
What are other non-skin related effects of topical steroids?
may worsen/ mask infections
systemic absorption
tachyphylaxis- decrease in response to anti-inflam effects
rebound flare of disease (esp. psoriasis)
What are antiseptics used for?
recurrent infections
antibiotic resistsance
wound irrigation
What conditions are topical antibiotics used for?
acne
rosacea
impetigo
infected eczema
What conditions require an oral antiviral?
eczema herpeticum; herpes zoster
What are topical antifungals used to treat?
candida
dermatophytes (ringworm)
pityriasis versicolor
Name 4 antipruritics
menthol
capsaicin (red chilli peppers)
camphor/phenol-pruritis ani (around the anus)
crotamiton
What are keratolytics used for?
viral warts
hyperkeratotic eczema and psoriasis
corn and calluses
to remove keratin plaques in scalp
What topical treatments can be used to treat psoriasis?
emollients and
- coal tar
- vit D analogue
- keratolytic
- topical steroid
- dithranol
What is the mode of action of imiquimod?
enhances innate and cell- mediated immunity and so has anti-viral and anti-tumour effects
What is imiquimod used to treat?
viral warts and superficial BCC
What do calicneurin inhibitors do?
suppress lymphocyte activation
what are calicneurin inhibitors used to treat
atopic eczema esp face and in children
What are the side efects of topical therapies?
burning or irritation
contact allergic dermatits
local toxicity
systemic toxicity
How many grams is needed for an adult to cover the whole bodyin ointment?
30g
