Percutaneous absorption

Question 1

what is percutaneous absorption

Answer 1

absorption through the skin

Question 2

what is the rate limiting step of percutaneous absorption

Answer 2

diffusion through the stratum corneum because it is highly keratinized

Question 3

what are the routes of percutaneous absorption

Answer 3

across the stratum corneum

via appendages

Question 4

what is the brick and mortar model of the stratum corneum

Answer 4

intercellular: using the lipid bilayer (aka mortar)
intracellular: using the cells (aka bricks)

Question 5

what is the paritition coefficient (P)

Answer 5

Ratio of concentration of drug in the SC to concentration of drug in the vehicle

Question 6

do you want a large P value or a low one

Answer 6

Larger the partition coefficient the more affinity the drug has for the skin
Want a drug with a high affinity for the stratum corneum
Want more hydrophobic drugs because they will got through the stratum corneum more readily than hydrophilic drugs
Select the drug coming as an acid or a base and not a salt as those will be more lipophilic

Question 7

are vehicle factors important in percutaneous absorption

Answer 7

YES: drug is released differently from different vehicle types

Question 8

what are vehicle factors that affect drug delivery

Answer 8

pH–>determines ionization of the drug (Non-ionized penetrates better)
Co-solvents–>concentrate drug on skin
Release of drug from vehicle–>optimize with the appropriate vehicle
Penetration enhancers–>temporarily increase permeability of the skin

Question 9

does diseased skin affect percutaneous absorption

Answer 9

for the most part increases absorption because the barrier is compromised

Question 10

what other skin factors play a role in percutaneous absorption

Answer 10

age of the skin
thickness of the stratum corneum
skin metabolism
circulation to the skin

Question 11

why does C1 initially increase when looking at Fick’s law

Answer 11

Drug accumulates on the surface: means C1 increases initially
If it doesn’t accumulate absorption will be slow

Question 12

what treatments target the skin surface

Answer 12

Camouflage or cosmetic preparations
Protective films–>barriers, sunscreens
Antifungal and antibacterial preparations

Question 13

what treatments target the stratum corneum

Answer 13

Emollients and moisturizers (increase water content)

Keratolytic (to remove dead cells)

Question 14

what treatments target the epidermis and dermis

Answer 14

Majority of dermatological agents target this area
Topical steroidal and non-steroidal anti-inflammatory agents
Local anesthetic agents
Antihistamines/anti-pruritic
Anticancer drugs

Question 15

what treatments target the systemic circulation via percutaneous absorption

Answer 15

hormone replacement therapy

others that have since become patches (nitro for angina, scopolamine for motion sickness)

Question 16

what treatments target skin appendages

Answer 16

Antiperspirants (sweat glands)–>aluminum salts
Exfoliants (acne)–>salicylic acid, tretinoin, benzoyl peroxide
Depilatories–>thioglycolates
Antibiotics–>clindamycin, erythromycin, tetracycline
Antifungals–>clotrimazole, miconazole

Question 17

what is the use of powders

Answer 17

Adhere little to skin

Primarily for hygienic purposes

Question 18

what is the use of liquids

Answer 18

Used as wet dressings
Oozing dermatoses
Chapped skin

Question 19

what is the use of ointments

Answer 19

Emollient, occlusive effect

Avoid in oozing conditions (cant absorb extra water) and acne

Question 20

what are shake lotions used for

Answer 20

Cooling and drying effect

Effective for: erythematous and papular dermatoses, vascular dermatoses, inflamed, irritated insect bites, hives

Question 21

what are pastes used for

Answer 21

Drying and absorbing effect

Effective for oozing, lichenified and keratotic conditions

Question 22

what are creams used for

Answer 22

Cooling, non-occlusive effect
Good moisturizers and emulsifiers (can take up liquids)
Non-greasy

Question 23

types of bases used in acne

Answer 23

liquids (water or alcohol based)
gels
creams, o/w emulsions
NOT occlusive

Question 24

types of bases used in dermatitis

Answer 24

absorption bases with oozing
Emulsions: because they have a moisturizing effect as well and can contain humectants
Better to use w/o emulsion to create a protective barrier
Creams, lotions, ointments

Question 25

types of bases used in psoriasis

Answer 25

occlusive (the more the better): hydrocarbons, silicone bases
creams
ointments with plastic wrap to increase hydration

Question 26

types of bases used in herpes simplex

Answer 26

protectant

cream

Question 27

types of bases used for corns and calluses

Answer 27

occlusive: the more the better (easier to remove the abrasion)

Question 28

bases used for tinea pedis

Answer 28

non-occlusive

o/w creams

Question 29

bases used for tinea capitits

Answer 29

non-occlusive
gels
creams

Question 30

what are topical steroids used for

Answer 30

relief of inflammation and itchiness

Question 31

what does fluorination of C9 on a corticosteroid do?

Answer 31

increases inflammatory activity

Question 32

what does addition to C17 or C21 on a corticosteroid result in?

Answer 32

influence solubility (more lipophilic substituent increases skin penetration)

Question 33

what does addition of alpha-alkoxycarbonyl to the C16 of a corticosteroid result in

Answer 33

antedrug and decreased systemic side effects

Question 34

how many classes of corticosteroids are there (name them)

Answer 34

7
Super/ultra potent (1)
High (2 and 3)
Intermediate (4 and 5)
 Low (6 and 7)

Question 35

how is potency of a corticosteroid determined

Answer 35

blanching assay

Corticosteroids vasoconstrict blood vessels on the surface of the skin causing it to change colours