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Stage 3 Case 1 > Patches > Flashcards

Patches Flashcards

1
Q

What are Patches for

A

Designed to deliver drugs across skin.

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2
Q

2 types of patches

A
  • Transdermal (systemic)—extended release.

- Transcutaneous (topical).

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3
Q

Durogesic D Trans

A

Fentanyl and 100 μg per h (release rate)

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4
Q

Where is Durogesic D Trans used?

A

Upper body or arm

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5
Q

How often do you use Durogesic D Trans?

A

Every 72 hours

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6
Q

Transdermal patch example

A

Durogesic D Trans

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7
Q

Where is Voltarol used?

A

Painful joint or region

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8
Q

How often do you use Voltarol?

A

1–2 times daily

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9
Q

Voltarol drug and strength

A

Diclofenac and 140 mg

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10
Q

Transcutaneous patch example

A

Voltarol

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11
Q

Transdermal delivery advantages (4)

A
  • Avoids hepatic first-pass metabolism (but skin could also metabolise drugs).
  • Non-invasive.
  • Extended release.
  • Readily applied and removable.
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12
Q

Transdermal delivery disadvantages (3)

A
  • Low deliverable doses.
  • Skin irritation.
  • Variable absorption.
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13
Q

Release liner

A

What is removed from the patch before it is applied onto the skin.

Its job is to prevent unwanted drug release, protect the formulation, protect the adhesive, and prevent contamination of the patch and the formulation.

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14
Q

Adhesive

A

Sticks to the skin

Some patches have the drug within the adhesive layer itself.

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15
Q

Backing layer

A

The backing layer provides, and anchor point for the formulation to stick on.

Provides protection from the outside environment.

Provides occlusion, important in maintaining a constant reasonable absorption rate

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16
Q

Reservoir & matrix patches:

A
  • Reservoir/matrix: Contains drug.

- Rate-limiting membrane/matrix: Controls drug release.

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17
Q

Where can the drug be put on a patch?

A
  • Drug in adhesive
  • Drug in matrix
  • Drug in reservoir
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18
Q

Disadvantage of drug in revisor

A

Easy to retrieve so can be easily misused.

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19
Q

Alternative to drug is revisor due to misuse.

A

Reformulation to drug in matrix.

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20
Q

Polyacrylates function (Durogesic DTrans)

A

Adhesive

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21
Q

Polyester/Ethylene vinyl acetate copolymer film function (Durogesic DTrans)

A

Backing film

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22
Q

Siliconised polyester function (Durogesic DTrans)

A

Protective release liner

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23
Q

Dipropylene glycol function (Matrifen)

A

Solvent

24
Q

Hydroxypropyl cellulose function (Matrifen)

A

Matrix

25
Q

Dimeticone function (Matrifen)

A

Matrix

26
Q

Silicone function (Matrifen)

A

Adhesive

27
Q

Ethylenvinylacetate (EVA) function (Matrifen)

A

Rate-controlling membrane

28
Q

Polyethylene terephthalate (PET) film function (Matrifen)

A

Backing film

29
Q

Fluoropolymer-coated polyester film function (Matrifen)

A

Protective release liner

30
Q

Which drugs are best absorbed in patches?

A

Small lipophilic drugs best absorbed

31
Q

Size of drugs are best absorbed in patches?

A

MW < 500 Da

32
Q

LogP of drugs are best absorbed in patches?

A

1 < log P< 4

33
Q

Layers for transdermal drug delivery?

A

Epidermis

Dermis

Hypodermis

34
Q

What is the epidermis split into?

A

Stratum corneum and viable epidermis

35
Q

What does the stratum corneum consist of?

A

Dead cells called keratinocytes.

36
Q

Stratum corneum

A
  • Rate-limiting diffusion barrier.

- Overall lipophilic, but there are hydrophilic and lipophilic domains.

37
Q

Where is the stratum corneum?

A

Outermost layer of the epidermis

38
Q

What happed once the drug passes the stratum corneum?

A

Once stratum corneum crossed, systemic absorption will occur to some extent.

39
Q

3 Drug absorption pathways

A

Paracellular pathway (intracellular route)

Appendageal pathway (shunt route)

Transcellular pathway (intracellular route)

40
Q

When would you not use a patch?

A

When large doses (low potency) are required or quick delivery.

41
Q

Why can you not deliver large doses or quick delivery with patch?

A

As it is too slow and cannot deliver large doses (low potency) to have therapeutic effect.

42
Q

Best type of drug for patch?

A

Small, lipophilic, and potent enough to only require a small drug to be effective.

43
Q

Paracellular pathway

A

The drug diffuses within the extracellular lipid matrix from the outer to the inner end of the stratum corneum.

44
Q

Paracellular pathway lipophilic drugs or hydrophilic drugs?

A

Lipophilic

45
Q

Why is the paracellular pathway low drug absorption rate?

A

As it needs to wind its way round the hydrophilic corneocytes due to the drug being lipophilic.

46
Q

Transcellular pathway

A

Diffuses quickly through the hydrophilic corneocytes and slowly through the extracellular lipid matrix.

47
Q

Why is the transcellular pathway low drug absorption rate?

A

As it diffuses slowly thorough the extracellular lipid matrix due the drug being hydrophilic.

48
Q

Transcellular pathway lipophilic drugs or hydrophilic drugs?

A

Hydrophilic

49
Q

Two key process that drive drug absorption via patches?

A

Diffusion and partitioning

50
Q

Partitioning

A

Where drug moves from one medium to another with different properties.

51
Q

Diffusion

A

Where drug moves from 1 spot to another within the same medium.

52
Q

Potts and Guy’s equation

A

Skin permeability

Predict skin permeability from drug properties:

  • Molecular weight (MW)
  • Lipophilicity (log P)
53
Q

Drug permeation rate in patch

A

Overall absorption rate increases with patch size.

54
Q

Drug absorption rate in patch per unit area

A

Absorption rate per unit area constant irrespective of patch size. The concertation gradient remains the same.

55
Q

What two condition would causes a drop in absorption rate within the same unit area?

A

If is not being cleared away quick enough from the skin by blood circulation.

So much drug has been absorbed, that only a little concertation of drug remains in the patch.

56
Q

What can change the release rate is the formulation is the same?

A

The SA of the patch. Release rate and patch size are directly proportional.

57
Q

Franz diffusion cell

A

Equipment to assess transdermal drug absorption in vitro.

Stage 3 Case 1 (12 decks)

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