Pharmacology & The Skin Flashcards
Describe the outer layer of the epidermis
The stratum corneum has a “brick and mortar” structure.
The bricks being an insoluble keratin matrix (corneocytes)
The mortar being an intercellular lipid layer made of ceramides, cholesterol, and fatty acids.
Name the three routes that medications can be absorbed through the skin
Intercellular route (most common)
Transappendageal route
Intracellular route
Name 3 factors that affect absorption through the skin
Water solubility
Molecular weight
Oil/water partition
Are hydrophilic drugs poorly or well absorbed through the skin? Why?
- Hydrophilic drugs are poorly absorbed
- As low partition through the lipid matrix of stratum corneum
What are benefits of topical medications for local use
Reduced systemic side effects
Why are glucocorticoids readily absorbed through the skin
They are small & hydrophobic drugs =>
Can easily penetrate intercellular lipid matrix
Topical glucocorticoids effects
- Lymphocytopenia - Suppress lymphocyte proliferation
- Reduced scar tissue - Inhibit collagen synthesis and fibroblast proliferation
- Anti-inflammatory - inhibit the synthesis and release of chemical mediators of inflammation, including histamine and prostaglandins.
Topical glucocorticoid indications
Allergic responses
Eczema
Psoriasis
Glucocorticoid MOA
Bind to intracellular receptors =>
Receptors dimerise & translocate inside the nucleus =>
Can bind to HRE & upregulate transcription OR
Can bind to negative HREs & down regulate transcription OR
Can bind to transcription factors & down regulate transcription
What influences the potency of topical glucocorticoids
Solubility of active ingredient & vehicle penetration
The composition of a topical vehicle can affect what two factors
Rate & extent of absorption
Gel vs cream vs lotion - which is typically more potent
Gel>cream>lotion
Describe transdermal drug delivery
Method of delivery that involves applying drug formulation directly onto intact & healthy skin for systemic use
Drug diffuses into the stratum corneum, epidermis, dermis & subcutaneous tissue, where it enters systemic circulation
name examples of drugs that can be sued as transdermal patches
Motion sickness
Analgesia
HRT & contraception
Smoking cessation
Name some advantages of TDD
Simple, convenient, painless
Excellent for steady & prolonged administration
No first pass metabolism in liver
