Topical Therapeutics in Dermatology

Question 1

Which layer of the skin is described as having a “brick-and-mortar” appearance? What are the “bricks” and “mortars”?

Answer 1

The stratum corneum of the epidermis; corneocytes are the bricks and intercellular lipids are the mortar

Question 2

The three ways drugs can pass through the skin are _______.

Answer 2

passive diffusion through tissue, seeping through pores in the brick-and-mortar network, and through apendageal structures

Question 3

List the drug factors that affect absorption.

Answer 3

Lipophilicity, vehicle composition, size, and concentration

Question 4

Ointments are _____.

Answer 4

water in oil emulsions

Question 5

Creams are ______.

Answer 5

oil in water emulsions

Question 6

Sites most amenable to gels are ______.

Answer 6

the oral mucosa and the scalp

Question 7

The benefits of ointments are __________. The downsides are _____.

Answer 7

high potency, low sensitization risk, hydrating; greasy, not useful for intertriginous sites or face

Question 8

A common unit of measurement for topicals is the ______.

Answer 8

fingertip unit (FTU), roughly 0.5 g; it is the amount the covers the distal phalange of the second digit with a 5 mm dispensing tube

Question 9

Foams are aerosolized gel matrices. What are their benefits and downsides?

Answer 9

They dry fast and don’t leave a residue, so they work well on hair-bearing areas.

Question 10

While most areas of the body are amenable to creams, clinicians should avoid creams on _______.

Answer 10

macerated areas (sites that have been damaged due to excessive moisture)

Question 11

One gram of cream covers _______.

Answer 11

roughly 10 cm^2 (ointment covers 10% more)

Question 12

There are seven classes of topical corticosteroids. Name a class one (most potent), class seven (least potent), and one in between.

Answer 12

1 = clobetasol propionate, 7 = hydrocortisone, and 4 = triamcinolone acetonide

Question 13

List the patient factors that affect drug absorption.

Answer 13

(1) anatomic location, (2) skin hydration, (3) presence of a barrier, and (4) occlusion

Question 14

Gels are _________.

Answer 14

semisolid emulsifications in alcohol; great for the mucosal surfaces or the scalp (because gels dry quickly); not great for fissures or macerated areas

Question 15

Foams have _______ potency.

Answer 15

strong (because the inactive volatile ingredients evaporate, leaving behind only the active ingredients)

Question 16

List some FTUs for various body parts.

Answer 16

Trunk (front or back) 7 FTU; arm 3 FTU; leg 6 FTU; foot 2 FTU

Question 17

How many grams of cream are needed to cover the entire body of an adult man?

Answer 17

20 g

Question 18

Describe the mechanism of glucocorticoid action.

Answer 18

Glucocorticoids bind to cytosolic receptors, which then dimerize and act as a transcription factor for several anti-inflammatory genes. This ultimately leads to the down-regulation of GM-CSF, nF-KB, and several interleukins.

Question 19

In patients with allergic contact dermatitis, what types of topical medications should be used cautiously?

Answer 19

Those that are water-based: water-based medications must have preservatives, which can be a source of ACD.