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PM3A > General skin > Flashcards

General skin Flashcards

1
Q

What is the role of the stratum corneum?

A

Mechanical cushioning to make skin robust - barrier

Regulation of water loss

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2
Q

What part of the epidermis goes wrong when you get:

  • eczema
  • psoriasis
A

Eczema - stratum corneum

Psoriasis = stratum basale due to hyperproliferation

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3
Q

What forms the stratum corneum?

A

Basal cells divide, migrate outwards and differentiate, then flatten to form the stratum corneum. (when basal cells divide they lose their nucleus and then they become filled with keratin)

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4
Q

What cells are the immune cells in the epidermis?

A

Langerhans cells which are dendritic cells - process microbial antigens.

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5
Q

What is the UV shield in the epidermis?

A

The malanocyte cells containing melanin pigment which is taken up by keratinocytes to protect from UV radiation

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6
Q

What is the role of keratinocytes?

A

Protection - produce keratin which is a fibrous protein helps give epidermis protective properties

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7
Q

What happens when there is a filaggrin mutation?

A

Reduced Natural moisturising factor and thus the skin is drier, loss of integrity and is a risk factor for hypersensitivity/allergy (IgE)

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8
Q

Where are the. sweat ducts, sebaceous glands, sweat glands, hair follicles contained in the skin?

A

Dermis

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9
Q

What cells are. the sensory receptors?

A

Merkel cells - they have. sensory nerve endings. for touch

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10
Q

What are the 2 types of sweat gland?

A

Eccrine (e.g. prevent body overheating, gland ducts empty. into pores which lead to the skin surface)
Apocrine (e.g. nipples, armpits, eyelids) - secrete fatty exudate, empty in hair follicles. Blocked in acne.

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11
Q

What part of the. skin is implicated in acne?

A

Sebaceous oil glands- sebum secretion is under. hormonal control

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12
Q

What is transdermal drug delivery?

A

Delivery across the skin for SYSTEMIC action

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13
Q

What is local drug delivery?

A

Delivery of drug at the site of action - so it acts at the site at which it is applied

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14
Q

What is topical drug delivery?

A

Acts at a site in the skin e.g. epidermis/dermis

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15
Q

What is the biggest barrier to drug delivery?

A

Outer stratum corneum - rate limiting structure for most drugs is multiple. lipid bilayers. Hence need the drug to be lipophilic

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16
Q

What are the 2 key aspects of drug formulation that drugs should have?

A

Lipophilic - better delivered

Lower MP - better absorbed

17
Q

Some advantages of transdermal delivery

A

Easy cessation if need, large surface area, avoids 1st pass metabolism

18
Q

What is the main route of drug delivery to skin?

A

Intercellular predominates at steady state

19
Q

What type of formulation would you use if you had:

  • oily
  • normal-dry
  • dry
A

oily - gel - water base
Lotions for normal/dry

Dry - creams

20
Q

What type of. formulation would you use if you had:

Hairy site

A

Lotions, gel, spray

21
Q

What type of. formulation would you use if you had:

a wet, vesicular, weeping lesion

A

Wet aqueous based - cream, lotion, gel

No alcohol

22
Q

What type of. formulation would you use if you had:

Dry, thickened, scaly lesion

A

Dry fatty e.g. ointment / paste

23
Q

What are the ideal drug candidate properties for delivery and what does it not account for?

A

Mwt 300-500
LogP 1-3.5 lipophilic
Aq solubility >100mg/mL. some

Does not account for potency

24
Q

If you wanted to deliver a drug:

for extended delivery through the skin - what would you. use?

A

Transdermal patch

25
Q

If you wanted to deliver a drug: for increased residence on the skin - what would you use

A

Semi solid

26
Q

If you wanted to deliver a drug: for rapid short term input of drug into skin - what would you use

A

Liquid

27
Q

what do we assume drives diffusion of drugs across the membrane? how do we show this?

A

Thermodynamic activity - shown as
Flux equation, use of franz cells
So concentration is not relevant, it is more important to focus on thermodynamic activity

28
Q

What is the role of emollients?

A

Moisture, trap in moisture by forming a protective film

e.g. diprobase, E45

29
Q

Why is alcohol useful excipient (provided the SC is in tact)?

A

It can enhance delivery via volatilisation and supersaturation - good solvent for. lipids and drugs must e lipophilic to get through SC

30
Q

What is the bioavailability of:

  • topical products
  • patches
A

Topical 1-3 % F

Patches 30-70% F

31
Q

What do saturated solutions do?

A

Have maximum thermodynamic activity to maximum diffusion and thus can even use low concentrations of saturated solutions to deliver drug

32
Q

What is occlusion?

A

The Stratum corneum equilibrates with the underlying wet dermis to stop trans-epidermal water loss but can cause irritation

33
Q

What do enhancers do?

Give examples

A

They interact reversibly with the skin to promote drug flux - they disrupt the SC lipid structure which is crystalline to get hydrophilic drugs through
examples are solvents e.g. ethanol, PPG, surfactants SLS, fatty acids e.g. oleic acid, hydrotropes e.g. urea.

34
Q

In a drug in adhesive patch - does the size relate to the dose delivered?

A

Yes - Surface area M^2.
Drug is in a rate limiting membrane.
If the patch is bigger it has a larger surface area and more delivered

35
Q

What other ways can you deliver drugs via skin and improve delivery?

A

Micelles nanoparticles, ethasomes
liposomes - they enhance the permaation of lipophilic drugs, fuse with surface and increase thermodynamic activity to increase drug content to tissue and have a reservoir effect

36
Q

What is a drug that causes occlusion that is bad?

A

Steroids - because they can have a rebound effect, get blanching. Steroids cause vasoconstriction so skin will go white (blanch) then if you cover the site a day later with something occlusive - rebound blanching. Water increases in SC and kicks steroids off the capillaries and they drug stay in the SC

37
Q

when someone puts a cream on - where is the drug really being delivered from?

A

when you rub a cream in it undergoes metamorphosis, so drug comes. from residue of the formulation rather than the actual cream as you are rubbing the cream in

38
Q

What type of patch can you cut?

what can. you cut?

A

if it is in a liquid reservoir you cannot cut it

Drug in adhesive you can cut

39
Q

What is a liposome?

A

Hydrophilic heads and lipophilic tails - contain hydrophilic drug and get through lipophilic membrane, enhancing diffusion and absorpion

PM3A (17 decks)

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