Dermatologic Pharmacology

Question 1

What is the primary barrier to absorption of substances through the skin (the rate-limiting step)? Why is anything ever absorbed?

Answer 1

Passage through the stratum corneum. Passive diffusion via a concentration gradient.

Question 2

Is drug absorption increased/decreased with hydration? What about with injured/diseased/ulcerated skin (eczema, psoriasis)? What about with retained keratin (icthyosis)?

Answer 2

Increased with hydration and injury/disease/ulcers that opens skin. Decreased with retained keratin.

Question 3

Regional differences in penetration?

Answer 3

Mucous membranes, scrotum, eyelids, face, chest/back, upper arms/legs, lower arms/legs, dorsa of hands/feet, palmar/plantar surfaces, nails.

Question 4

3 important drug variables that increase absorption?

Answer 4

High concentration (more important than volume), lipophilicity, small molecular size

Question 5

Strongest versus weakest vehicle? Should vehicles be irritants?

Answer 5

Ointment versus solution, based on lipid content. Irritants alter skin barrier and increase absorption.

Question 6

4 important innate skin variables that increase absorption?

Answer 6

Thin stratum corneum, increased cutaneous vasculature, increased SA, mucosal surface

Question 7

What is an ointment? Hydrating or not? Potency?

Answer 7

“Water in oil emulsion” “Hydrating” “Strong potency”

Question 8

What is a cream? Hydrating or not? Potency?

Answer 8

“Oil in water emulsion” “Some hydration” “Moderate potency”

Question 9

What is a gel? Hydrating or not? Potency?

Answer 9

“Semisolid emulsion in alcohol base” “Drying” “Strong potency”

Question 10

What is a lotion/solution? Hydrating or not? Potency?

Answer 10

“Powder in water (some with oil) “Drying (variable)” “Low potency”

Question 11

What do powders do with moisture and friction? How do they adhere to the skin?

Answer 11

Absorb moisture, Reduce friction, Adhere poorly and clump.

Question 12

Are oils (greases) protective? Are ointments?

Answer 12

Greases are protective, Ointments are occlusive

Question 13

With Candida in a body fold, what should treatment be?

Answer 13

Cream (hydrate) then powder (prevent recurrence)

Question 14

When are pastes useful?

Answer 14

Ulcers, Chronic dermatoses

Question 15

When are gels useful?

Answer 15

Hairy areas – They allow for greater penetration than lotions

Question 16

What is a gel?

Answer 16

Liquid converted to a semisolid by addition of a polymer (“liquid in a mesh”)

Question 17

What is a paste?

Answer 17

“A smooth viscous mixture that has adherence-like properties”

Question 18

Where are solutions most useful for?

Answer 18

Scalp – They penetrate through hair and leave no residue

Question 19

AKA oil-in-water? Is this hydrating?

Answer 19

Vanishing cream; DRYING (water evaporates)

Question 20

AKA water-in-oil? Is this hydrating?

Answer 20

Oily cream; some hydration

Question 21

What is an aerosol?

Answer 21

“Solid/liquid suspended in a gas”

Question 22

What is a foam?

Answer 22

“A substance formed by trapping pockets of gas in a solid/liquid”

Question 23

How many classes exist for glucocorticoids? How are they ranked?

Answer 23

Seven classes: Class 1 (“Super-Potent’”) to Class 7 (“Mild”)

Question 24

Glucocorticoid (steroid) side effects?

Answer 24

Atrophy/thinning of skin/collagen (“steroid atrophy”), stretch marks, telangiectasias, acne, purpura, pigmentary changes, growth of bacteria, cataract or glaucoma if applied near eye with long term use; Systemmicaly affects the hypothalamic-pituitary-adrenal axis and can cause growth retardation (especially in children, because they will absorb better with an increased SA:V ratio)

Question 25

UVA & UVB light therapy mxn?

Answer 25

UV therapy alters the immune response in the skin: Immunosuppression of T-cells via type I or type II reactions: mono- or bifunctional adducts in DNA

Question 26

UV light therapy for?

Answer 26

Inflammatory conditions: psoriasis, atopic dermatitis, CTCL, lichen planus (NOT useful for non-inflammatory conditions)

Question 27

UV light therapy side effects?

Answer 27

Skin cancer, thinning/leathering of the skin

Question 28

UV light therapy used with?

Answer 28

Psoralens (photosensitizing agents that increase efficacy)

Question 29

What agents besides psoralens sensitize skin to light therapy?

Answer 29

Phenothiazines, thiazides, sulfonamides, NSAIDs, tetracycline, benzodiazepenes

Question 30

Psoralens belong to what class of compounds?

Answer 30

Furocoumarin