The Skin barrier

Question 1

What are the components of the extracellular stratum corneum?

Answer 1

Ceremides
Cholestrol
Free fatty acids

1:1:1 ratio

Question 2

Which skin level is the primary barrier to water soluble drug absorption and hydration?

Answer 2

Stratum Corneum

Question 3

Is the stratum corneum acidic or basic?

Answer 3

Acidic - “acidic mantle”

Very impt for barrier generation
Loss of the PH gradiant, leading to neutralisation of the stratum corneum is a common feature of skin disease such as AD

Question 4

What factors affect topical drug absorption?

Answer 4

Hydration of the skin
Occlusion
Addition of excipients (ethanol, propylene glycol)
Site of application (scrotom > face > tuck > palms > sole > nails

Patient factors:
- age of the skin
- presence of disease

Properties of the medicaiton
- base
- molecule size
- lipophillicity
- concentration