Pharmacology and the Skin Flashcards
Describe the topical route?
Drug (in a pharmacologically inactive vehicle) applied to the surface of the skin. Most often used for local effects.
Describe the water content of different topical vehicles?
lotions ˃ creams ˃ ointments ˃ gels ˃ pastes ˃ powders
Describe the subcutaneous route?
Drug delivered by a needle [inserted into the fatty (adipose) tissue just beneath the surface of the skin]
Describe the transdermal route?
Drug is usually incorporated into an adhesive patch applied to the epidermis
What is the single most important barrier to drug penetration into the skin, or diffusion across it
Stratum corneum- the keratinocyte layer
A lipophilic drug in lipophilic base is ______________
soluble in both vehicle and skin and partitions between the two
A Lipophilic drug in hydrophilic base is _____________
more soluble in skin and preferentially partitions into it
A Hydrophilic drug in lipophilic base has __________________
limited solubility in both vehicle and skin and partitions into it weakly
Hydrophilic drug in hydrophilic base is___________
soluble in vehicle but not skin and remains on the surface of it
Describe how skin hydration is important when thinking about topically applied drugs. When may this be helpful?
Water retention breaks down stratum corneum to allow drugs to diffuse more readily into the skin. Have an oily base to promote skin hydration. Cover skin in cling film to stop perspiration escaping.
Describe the molecular action of glucocorticoids
Glucocorticoids are lipophilic molecules - enter cells by diffusion across the plasma membrane (1) Within the cytoplasm, they combine with GR (2) producing dissociation of inhibitory heat shock proteins (e.g. HSP90). The activated receptor translocates to the nucleus aided by ‘importins’ (3).
Within the nucleus activated receptor monomers assemble into homodimers(4) and bind to glucocorticoid response elements (GRE) in the promotor region of specific genes
The transcription of specific genes (5) is either ‘switched-on’ (transactivated) or ‘switched off’ (transrepressed) to alter mRNA levels (6) and the rate of synthesis (7) of mediator proteins (
What is the subcutaneous route used for?
many protein drugs (e.g. insulin) and suitable for administration of oil-based drugs (e.g. steroids)
Main reason for subcutaneous route?
Allows for slow absorption
Describe an emollient
- Enhance rehydration of epidermis
* For all dry/scaly conditions esp. eczema
How much emollient do you need to prescribe per week?
300-500g
Example of a mild corticosteroid?
Hydrocortisone 1%
2 examples of moderate corticosteroids?
modrasone and clobetasone butyrate
2 examples of potent corticosteroids?
Mometasone and betamethasone valerate
Example of a very potent corticosteroids
Clobetasol proprionate
How much corticosteroid ointment is needed for one application to adult body?
20-30g
1 finger tip unit of corticosteroid should cover?
2 hand areas
Side effects of topical steroids?
Thinning of the skin, purpura and stretch marks. Steroid rosacea, perioral dermatitis, fixed telangecstasia (visible broken capillaries)
Can be rebound flare of the disease in psoriasis
What will emollients mixed with water such as creams as lotions contain? What does this mean?
Will contain a preservative and the preservative may irritate the skin. However this means they last longer and won’t be contaminated. Ointments do not contain a preservative so need to be careful about bacterial contamination.
When is zinc oxide used?
used in pastes and wet wraps as it helps promote healing in dry skin
What are gels?
Thickened aqueous solutions
