Multilayer Diffusion

Question 1

What does a molecule encounter as it moves throughout the body?

Answer 1

Multiple consecutive layers.

Question 2

How is the overall diffusion rate and flux described?

Answer 2

By an overall permeability coefficient representative of the whole system, termed the apparent permeability.

Question 3

Who created a model to study the absorption of drug from a topically applied product?

Answer 3

Takeru Higuchi.

Question 4

When molecules diffuse through series/consecutive layers, the layer in which diffusion encounters the greatest ______ is rate-limiting for the entire pathway and used to determine _________.

Answer 4

Resistance; apparent permeability.

Question 5

To eliminate patient-to-patient physiologic variability, many drug products are designed to have a ______________ boundary built into the product.

Answer 5

Rate-limiting.

Question 6

What is resistance?

Answer 6

The difficulty a molecule has moving through a given layer.

Question 7

Resistance is the reciprocal of?

Answer 7

Permeability.

Question 8

As resistance increases, what happens to diffusion through a medium?

Answer 8

Permeability decreases.

Question 9

What is the overall permeability mathematically?

Answer 9

The sum total of the resistance of each layer in the series.

Question 10

Ptot describes the total permeability of the system when?

Answer 10

No layer is deemed limiting to a drug’s passage through the entire series.

Question 11

What is used to describe the multi-step process by which API molecules move from an aqueous delivery compartment across a physiological membrane?

Answer 11

The unstirred water layer.

Question 12

Who created a method to test the unstirred water layer diffusion?

Answer 12

Franz.

Question 13

How many consecutive layers do molecules need to diffuse through before arriving at the receptor compartment?

Answer 13

3.