Transdermal drug delivery

Question 1

What are the advantages of TDD?

Answer 1

avoids GIT
bypasses first pass
controlled rate of drug delivery
reduced dosing

Question 2

What is the structure of the skin?

Answer 2

viable epidermis
dermis
subcutaneous fat
underlying tissue

Question 3

In Fick’s law what does J define?

Answer 3

flux or amount of drug passing through a unit area per time

Question 4

What are the optimal physics-chemical properties for a good drug candidate of TDD?

Answer 4

MW 300-500 Da
Log P 1-3.5
solubility > 100micrograms/mL
neutral on skin pH 5

Question 5

What two methods are used to estimate drug flux across the skin?

Answer 5

mathematical

in vitro permeation

Question 6

What are the characteristics of the following parts:
release liner
pressure sensitive adhesive
backing layer

Answer 6

Release layer: must be occlusive and peeled off before applying to skin

pressure- must stick to skin, non irritating and easily removed

backing - must be occlusive and flexible

Question 7

What are the disadvantages of transdermal patches?

Answer 7

allergy, irritancy 
can be cut 
fragile
still contain drug after use
drug release rate increased with temp 
variability  in designs 
administration frequency and site