Transdermal Drug Delivery (D2)

Question 1

Describe the anatomical breakdown of the skin

Answer 1

Stratum Corneum (Surface)
Viable skin (Made up of Viable epidermis and viable dermis)
Dermal microcirculation (capillaries)

Question 2

In transdermal delivery what is meant by partition and partition coefficient?

Answer 2

• Partition is the interface between 2 phases, eg skin and patch
• Partition coefficient is the rate of diffusion of a drug across the interface

Question 3

How do we measure drug permeation through skin in a lab?

Answer 3

• Using a diffusion cell system
  1) A membrane (sheet of skin) is used to divide 2 chambers, one containing the transdermal drug and the other containing target cells
  2) The drug diffuses across the skin barrier
  3) the permeation rate is calculated from level or speed that the cells begin responding to the drug

Question 4

What does this image show

Answer 4

• Once the drug has permeated through the skin it enters the blood stream (central compartment)
• Either is is delivered to the target tissues and diffuses into them (Peripheral compartments) or Metabolised (k10)

Question 5

What is the general process of drug formulation to release

Answer 5

Formulation
In-vitro study (skin permeation test)(Verification)
In-vivo study (animals) (Validation)
In-silico study (computer modelling and Simulation)
Clinical trials

(As much risk mitigation before trials)

Question 6

What is the benefit of using this model?

Answer 6

• Mitigates as much risk as possible to human patients
• Provides good predictions
• Optimises the type of Transdermal system early days resulting in lower R&D costs

Question 7

What is Ficks first Law

Answer 7

Question 8

What is Ficks Second Law

Answer 8