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PY352 > Transdermal delivery > Flashcards

Transdermal delivery Flashcards

1
Q

What is the counselling advice for patches?

A

Patch should be removed after 3-4 days (or once a week for 7 day patches) and replaced with a fresh patch on a slightly different site; recommended sites; clean, dry, unbroken skin on trunk below waistline. Not to be applied on breast or under waistband. If patch falls off in bath, wait for skin to cool down before applying new patch.

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2
Q

Nicotine patches have either ___ hour or ___ hour patches, once daily. The ___ hour patch is if there are ____ _________.

A

16
24
16
sleep disturbances

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3
Q

Buprenorphine or Fentanyl patches vary from ___ day or ___ day patches.
Do not cut them or allow the gel to get into your _____. If it does, wash with _____, not ____ or _______.
TAKE CARE ON DISPOSAL - ___ patch so that _______ goes to _______.

A 
3
7
hands
water
soap
alcohol 
fold
adhesive
adhesive
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4
Q

What are the psychological aspects of transdermal patches?

A
  • Preference
  • Memory
  • Control
  • Particular patient groups
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5
Q

Expand on preference aspect of transdermal patches

A
  • location
  • appearance
  • reassurance of drug administration
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6
Q

Expand on memory aspect of transdermal patches

A
  • less frequent administration

- decrease non intention non adherence

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7
Q

Expand on control aspect of transdermal patches

A
  • can remove if there are unwanted side-effects

- reduce intentional non-adherence

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8
Q

What are some advantages of transdermal patches?

A
  • avoids 1st pass GI and hepatic metabolism
  • absorption is consistent
  • variety of skin sites to avoid local irritation
  • therapeutic blood levels are achieved at lower absorbed dosages
  • can stop dose via removal
  • possible improved patient compliance
  • selected delivery
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9
Q

What are some limitations/ disadvantages of transdermal patches?

A
  • drug needs to be potent
  • drug needs to be effective when delivered over a long period of time
  • may not have same benefits as existing methods
  • may be uncomfortable to wear
  • drugs that require high blood levels cannot be administered
  • may not adhere to all skin types
  • drug or drug formulation may cause skin irritation or sensitisation
  • may not be economical
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10
Q

What are some drug classes used in transdermals?

A
  • anti diabetic agents
  • anti depressant agents
  • anti hypertensive agents
  • thyroid agents
  • antihistamines
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11
Q

Why do so few drugs go across the skin?

A

due to structure of skin barrier and physicochemical properties of the drug and its dosage form

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12
Q

Describe the skin structure from top to bottom

A
  • Stratum corneum
  • Viable epidermis
  • Dermis
  • Subcutaneous fat
  • Underlying tissue
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13
Q

The two functions of the skin are _______ and _______.

A

mechanical

protective

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14
Q

Expand on mechanical function of the skin

A
  • it is elastic
  • distention without disruption
  • interface with the outside world; heat, pressure, touch
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15
Q

Expand on the protective function of the skin

A
  • It acts as a microbiological barrier; microbial growth cannot occur due to short chain fatty acids from glands
  • level of stratum corneum
  • aided by sloughing of terminal squames
  • chemical barrier
  • blocks access of exogenous materials
  • controls loss of water, electrolytes and other endogenous materials
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16
Q

Radiation: Cellular damage is caused by -

A

UV (300-400nm). The pigment melanin is produced to absorb this harmful radiation

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17
Q

What is produced by the skin to protect us from harmful UV radiation (300-400nm)?

A

Melanin - pigment

18
Q

How does the skin act as a heat barrier?

A
  • The stratum corneum is a poor heat insulator.
  • It is the body’s largest interface with the environment has a role in regulation of body temperature via sweating.
  • If the temp is too high; massive peripheral vasodilation (sweat)
  • If temp is too low; vasoconstriction (piloerectus)
19
Q

What are appendages?

A

Deeper epidermal tissues due to invagination at the hair follicle. They have a larger surface area and are a morphologically distinct area

20
Q

What part of the skin is a potential route for drug delivery and how?

A

Appendages.

By deposition and surface morphology, but also facilitated delivery e.g. iontophoresis.

21
Q

What other structure has similar structure issues as hair follicles?

A

A pore. It also has the issue of opposing flow from the gland to be considered

22
Q

What is highly unlikely in terms of drug delivery and sweat gland?

A

Passive diffusion controlled absorption

23
Q

What is the difficulty of using skin as a target?

A

Stratum corneum function is to inhibit exogenous materials from coming in. It is also lipophilic in nature, is dense and has a lack of water therefore provides a unique barrier to drug absorption across the skin. Therefore, in order to understand percutaneous penetration of exogenous chemicals, we need to focus on the stratum corneum

24
Q

Where is the thickest stratum corneum barrier?

A

soles of the feet

25
Q

Where is the thinnest stratum corneum barrier?

A

eyelids, scrotum

26
Q

The stratum corneum is very thin but

A

very lipophilic and very thin stratified corneum

27
Q

What are some factors that affect percutaneous absorption?

A

Physiological
Physicochemical
Drug/Vehicle

28
Q

What are some physiological factors that affect percutaneous absorption?

A
  • skin hydration
  • skin condition
  • occlusion
  • skin age
  • regional variation
  • blood flow
  • race
  • gender
  • skin temperature
  • skin binding
29
Q

What are some physicochemical factors that affect percutaneous absorption?

A
  • molecule weight
  • partition coefficient/ lipophilicity
  • particle size
  • ionisability
  • solubility
  • chemical structure
30
Q

What are drug/ vehicle factors that affect percutaneous absorption?

A
  • drug/ vehicle interactions

- solubility of drug in excipients

31
Q

In order for the drug to be absorbed through the skin, they must

A

dissolve in the stratum corneum

32
Q

How does melting point affect if a drug will absorb through the skin or nah?

A
  • Higher melting points e.g. morphine will not penetrate well
  • Lower melting points e.g. nicotine will penetrate well
33
Q

Which drugs work best in TDDD? Hydrophillic, Lipophillic…?

A

Intermediate drug which exhibits both lipids and aqueous properties.

34
Q

The ‘Bricks and Mortar’ model of the stratum corneum states that intercellular means

A

around/ between skin

35
Q

The ‘Bricks and Mortar’ model of the stratum corneum states that transcellular means

A

through skin

36
Q

The ‘Bricks and Mortar’ model of the stratum corneum states that transappendageal

A

through the invaginated part of epidermal tissue

37
Q

If drug is too lipophillic,

A

they will stay there and not diffuse through the aqueous tissues in the rest of the skin

38
Q

If drug is too hydrophillic,

A

they will not even get through the stratum corneum barrier

39
Q

What is permeability data?

A

It is the measure of how much drug passes the skin in a given period of time. It is the rate of drug delivery

40
Q

What can be added to alter the structure of the stratum corneum?

A

Add a chemical penetration enhancer

41
Q

What is a chemical penetration enhancer?

A

This is a chemical that interacts with the skin lipids and changes the structure of the stratum corneum and thus changes its permeability. e.g. DMSO.
IT HAS TO BE PHARMACOLOGICALLY INACTIVE AND FIT FOR ITS PURPOSE

42
Q

What is important for adhesion in transdermal patches?

A

Good skin contact

Good bonding between laminating layers

PY352 (25 decks)

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