pharmacology 1 Flashcards
What is the main barrier to drug absorption in the skin?
-Describe the brick and mortar model
Stratum corneum
-Bricks = Corneocytes, these are highly cross linked and held together by corneodesmosomes Mortar = multiple bilayers of lamellar structures of intracellular lipids (hydrophobic
name the 6 different types of vehicle
ointment, creams, gels, lotions, pastes, pwders
Equation for the rate of absorption of a drug
Rate of absorption = (diffusion coefficient x partition coefficient/length of diffusion pathway) x conc of drug in vehicle
effect of drug solubility on delivery?
when topically applied only the soluble fraction of drug provides driving force for absorption e.g. excessive non-dissolved drug in a transdermal patch will provide constant delivery rate and increased duration
How can absorption through the Stratum corneum be improved? (3)
Hydration of the skin by occlusion e.g. vehicle
include excipients e.g.clingfilm
increase solubility of drugs
Glucocorticoids
- administration and use?
- General action
- Molecular mechanism of action (4)
-topical use in atopic eczema
-anti inflammatory and immunosuppressant
cause vasoconstriction
anti proliferating action on keratinocytes and fibroblasts
-lipophillic, enter via diffusion across the plasma membrane
in cytoplasm combine with and activate the GR alpha receptor which translocates to nucleus
activated receptor monomers bind to homodimers and bind to GRE in promoter region of the gene
Transcription of some genes is switched on or off to alter mRNA and synthesis of mediator proteins
Subcutaneous administration
- advantages
- disadvantages
-slow absorption due to poor vascular supply
protein drugs
oil based drugs (steroid)
depot- slow release
-volume limited
Transdermal Drug delivery
- drug type
- advantages
- disadvantages
-LMW, moderately lipophilic, short 1/2 life
-steady rate delivery
avoid 1st pass metabolism
convenient and painless
-few drugs suitable
cost
allergies
