Patches

Question 1

What are patches designed to do?

Answer 1

Deliver drugs across the skin

Question 2

What are the 2 routes of administration?

Answer 2

Transdermal (systemic)
Transcutaneous (local)

Question 3

How does transdermal work?

Answer 3

Skin permeation

Question 4

How does transcutaneous work?

Answer 4

Skin penetration

Question 5

Where do you put transdermal?

Answer 5

Upper body/arm

Question 6

Where do you put transcutaneous?

Answer 6

Painful joint/region

Question 7

What is an example of a transdermal patch?

Answer 7

Fentanyl

Question 8

What is an example of transcutaneous patch?

Answer 8

Diclofenac

Question 9

What are the advantages of patches?

Answer 9

Avoids 1st pass
Non-invasive
Extended release
Readily applied + removable

Question 10

What are the disadvantages of patches?

Answer 10

Low deliverable doses
Skin irritation
Variable absorption

Question 11

What’s in a patch?

Answer 11

Release liner
Adhesive
Backing layer

Question 12

What is a release liner?

Answer 12

Protects adhesive, prevents unwanted drug release + contamination

Question 13

What is an adhesive?

Answer 13

Sticks to skin

Question 14

What is a backing layer?

Answer 14

Protects formulation

Question 15

What are the 3 patch designs?

Answer 15

Drug in adhesive
Drug in reservoir
Drug in matrix

Question 16

What is in a reservoir patch?
Durogesic

Answer 16

Backing layer
Drug reservoir
Rate controller
Adhesive layer
Release liner

Question 17

What is the function of the polyacrylates excipients?

Answer 17

Adhesive

Question 18

What is the function of the polyester/ethylene acetate copolymer film excipients?

Answer 18

Backing layer

Question 19

What is the function of the siliconized polyester excipients?

Answer 19

Removable release liner

Question 20

What is the function of the dipropylene glycol excipients?

Answer 20

Drug matrix

Question 21

What is the function of the hydroxypropyl cellulose excipients?

Answer 21

Drug matrix

Question 22

What is the function of the dimeticone excipients?

Answer 22

Adhesive/drug matrix

Question 23

What is the function of the EVA excipients?

Answer 23

Rate controlling membrane

Question 24

What is the function of the PET excipients?

Answer 24

Backing layer

Question 25

Describe the structure of skin

Answer 25

TOP
Stratum corneum + viable epidermis = epidermis
Dermis (richly vascularised)
Hypodermis
BOTTOM

Question 26

Describe the stratum corneum

Answer 26

Primary skin barrier
Outermost epidermal layer
Corneocytes
Extracellular lipid matrix

Question 27

Because the stratum corneum is the main skin barrier, what does this mean?

Answer 27

Rate-limiting
Drug must cross this to be absorbed

Question 28

What criteria of drugs are best absorbed?

Answer 28

<500 Da
LogP 1-4
Several mg/day = quite potent

Question 29

What is drug release rate proportional to?

Answer 29

Patch size
= larger the patch
= more drug released per unit time
= greater strength/dose

Question 30

What are the different diffusion mechanisms?

Answer 30

Transcellular = through the cells (lipophilic route)
Paracellular = around the cells

Question 31

What does the Franz diffusion cell assess?

Answer 31

Transdermal drug absorption in vitro

Question 32

How does the Franz diffusion cell work?

Answer 32

Skin is sandwiched between donor chamber + receptor chamber
If drug is found in receptor fluid
= WORKS

Question 33

How do you increase dermal drug absorption?

Answer 33

Increase dermal drug flux
Modulate Kp