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SOM 3 > Transdermal > Flashcards

Transdermal Flashcards

1
Q

what are the main layers in the skin?

A

dermis and hypodermis

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2
Q

what’s the main role of hypodermis?

A

insulation and protect against mechanical strength

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2
Q

what’s the main components of dermis? & why may that be significant?

A

its made out of collagen and elastin dispersed in a gel, Maintaining the strength

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3
Q

what environment does the dermis sit in?

A

hydrophilic environment

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4
Q

what happens when mechanical strength isn’t absorbed by the hypodermis?

A

causes the capillaries to burst = blood accumulation = bruising

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5
Q

what is the hypodermis also known as?

A

subcutaneous layer

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6
Q

what is the major barrier for absorption in the skin?

A

hypodermis

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7
Q

what are some main components found within the skin?

A
  • eccrine sweat gland
  • muscle
  • hair follicles with Sebaceous glands
  • meissner corpuscle
  • pacini corpuscle
  • blood vessels found in the dermis
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7
Q

what does the eccrine sweat gland do?

A

release sweat to regulate heat to control body temperature

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8
Q

what is the function of the blood vessels in the skin?

A

vasodilation to dissipate heat to control body temperature; vice versa.

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9
Q

what is the function of the muscles in the skin?

A

responsible for goose bumps

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10
Q

what is the function of the sebaceous glands?

A

formation of sebum

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11
Q

what is the function of the meissner corpuscle in the skin?

A

sensing touch

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12
Q

what is the function of the pacini corpuscle in the skin?

A

sensing pressure

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13
Q

what does the epidermis protect you from?

A
  • trauma
  • chemicals
  • sun rays
  • too much water / heat
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14
Q

what’s the difference between the epidermis and dermis in relation to size?

A

epidermis thinner than the dermis

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15
Q

what are the main layers of the epidermis (from young/bottom to old/top)?

A

base layer, prickle cell layer, granular layer, horny layer

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16
Q

how long does it take for the base layer to mature and migrate to the horny layer?

A

a month

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17
Q

what happens to the shape and structure of the cells as the base layer migrates and matures into the horny layer?

A

loses general shape of the cell,

cell loses it nucleus as the out layer is composed of dead cells

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18
Q

what cell types are found within the base layer? and what do they do?

A

keratinocytes (main type); melanocytes (produce melanin) and langerhan cells (T cell response for an immune response)

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19
Q

what cell types are found within the prickle cell layer? and what do they do?

A

mainly keratinocytes and some langerhan cells (for immune response) and some desmosome junctions to hold cells together

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20
Q

why may regeneration for the epidermis take longer? and where may this take place?

A

if it recieves a lot of friction;

palms of the hand/ soles of the feet

21
Q

under what conditions does the regeneration of the epidermis occur at a faster rate?

A

dandruff and psoriasis

22
Q

what are the two layers of the horny layer ? what environment do they have?

A

lipid based ‘mortar’ - lipophilic
protein based ‘brick’ - hydrophilic (formed by keratin)

23
Q

when are medicated plasters used?

A

for local effect
to mainly target nerve endings in the dermis, must still be able to pass through the dermis

24
Q

what are some examples of medicated plasters?

A
25
Q

what are the features of nails?

A

keratinised tissue (80% hard keratin)

26
Q

what are some examples of topical treatments used for the nail?

A
  • fungal infections
  • nail psoriasis
27
Q

what problems are associated to nail topical treatment?

A

difficult to drug deliver, therefore weeks of treatment may be necessary in order to see any results

28
Q

what is the first barrier for drug formulations crossing the skin?

A

epidermis - stratum corneum (outer layer of the epidermis)

29
Q

what are the advantages of transdermal drug administration?

A

Avoids all the disadvantages of the oral route!
Non-invasive and ease of administration
Controlled release
Low frequency of administration
Drug administration can be stopped quickly Easy to identify in cases of emergency
self administration without training needed

30
Q

why can the drugs effects still be felt after the removal of the transdermal patch?

A

as the drug accumulates and forms a reservoir within the stratum corneum which allows drug absorption to continue

31
Q

what are the disadvantages of transdermal drug administration?

A

Not suitable for “bolus’’
Only suitable for potent drugs
-active at doses < 10 mg/day …with the right properties!
Skin sensitisation/irritation
Skin first-pass effect still possible for some drugs
-Pre-systemic metabolism
-Less extensive than from GIT
- Likely minor role in drug elimination from patch
-Mostly in the viable epidermis
- CYT P450 and other metabolic enzymes
- not used in emergencies
big portion of the drug remains within the patch

32
Q

why can’t non-potent drugs be used for transdermal use?

A

due to the drug being non-potent, a large volume of drug would be needed to reach therapeutic effects, this will cause the drug packaging to become too large = a low patient compliance

33
Q

what do conditions such as psoriasis do?

A

increase a thickness of stratum corneum affecting the drug permeation

34
Q

what’s the anatomical variation of skin thickness (from the highest permeability to the lowest)?

A

Epigenital region
Scalp, head and neck
Trunk (chest, belly, back)
Arms/Legs
Palms/soles

35
Q

what are the physicochemical properties that are desired for transdermal drug delivery?

A

MW 100-800 Da (ideal <400-500)

1<Log P <4-5 (ideal 2-4)

dose of 10mg/day

affinity for vehicle - too much affinity to the patch/vehicle will not allow the drug to be used for its desired effects

36
Q

what does ethanol do within transdermal formulations?

A

permeation enhancement
leaves a film on the skin upon evaporation

37
Q

label the following

A
38
Q

how is inter patient variability minimised within reservoir patches?

A

by the rate controlling polymer membrane

39
Q

why may there be drug present on the adhesive layer of a reservoir patch? what is the importance?

A

due to the diffusion/saturation to the adhesive layer during storage

causes dose dumping = overdose as the drug is absorbed instantly

40
Q

what is the release rate typically like for a reservoir patch?

A

zero order due to being controlled by changing the properties of the membrane

41
Q

label the following

A
42
Q

what are features of a matrix layered patches?

A

have one or more layers

drug may be dissolved or suspended in a polymer matrix

43
Q

what is the release rate typically like for a matrix patch?

A

drug dissolved in a polymer matrix - first order

drug suspended in a polymer matrix - zero order

44
Q

what is the release rate typically like for drug in adhesive layer?

A

typically first order - patient variability

45
Q

what advice would you give to your patient who is using transdermal patches?

A

Instructions provided in the PIL
- Alternate sites of application
- May need to cut hair (do not wet-shave or use hair-removal cream)
- Skin should be clean, not too oily, not irritated, broken or callused
Do not cut or modify the patch
Remove carefully, taking care not to touch the adhesive
Press firmly against the skin, hold in place for a few seconds
Place where it won’t be rubbed off by friction
Can generally be left while bathing/swimming/showering
Sensitivity/intolerance/irritation can happen
After removal, fold in half so that the adhesive layers stick together
Residual drug may be toxic to children and pets
Provide advice if patch falls off or was not replaced in time Lag time to onset
Remove before MRI - Backing layer may contain metal

46
Q

what are the ways we can physically enhance permeation of transdermal patches?

A

Iontophoresis
sonophoresis
micro- and nanoparticles
micro needles

47
Q

how does iontophoresis enhance permeation?

A

using a small electric current to support drug transport

48
Q

how do ionised drugs move in iontophoresis?

A

by electrostatic repulsion

drug reservoir is placed under the electrode with the same charge as the drug - the repulsion drives diffusion of the drug through the skin

49
Q

how do neutral drugs move in iontophoresis? and when is it used?

A

by electro-osmosis

movement of water and neutral molecules with migrating ions

  • used for glucose monitoring ‘reverse’ iontophoresis
50
Q

how does sonophoresis work?

A

using ultrasound enhanced drug transport

by causing vibrations in the skin and temporarily increasing the pore size between cells allowing an increase in drug absorption

51
Q

what are some examples where sonophoresis works?

A

lidocaine
salicylic acid
- gels, creams and lotions

52
Q

how does micro and nanoparticles work for enhancing permeation?

A

Targeted delivery through hair follicles thru Microparticles: reservoir effect and sustained drug release
Liposomes and derivatives - increase permeation

SOM 3 (26 decks)

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