Drug Absorption

Question 1

What are the factors that determine drug absorption across a membrane?

Answer 1

1. Characteristics of the membrane
2. Mechanism of passage across membrane
3. Dwell time of drug-membrane interface
4. Physicochemical characteristics of the drug
5. pH of the microenvironment
6. Surface area of absorptive surface

Question 2

Where is the site in the GI tract where most drug absorption occurs?

Answer 2

The small intestine is the primary site of absorption after oral administration because of its very high surface area.

Question 3

What are the mechanisms by which drugs cross biological membranes?

Answer 3

Paracellular diffusion, transcellular diffusion, facilitated diffusion, active transport and endocytosis.

Question 4

What are the differences between the two forms of carrier-mediated absorption? Facilitated diffusion and active transport.

Answer 4

Facilitated diffusion involves a transport protein which moves a drug with a concentration gradient.

Active transport involves a transport protein and also requires energy to move a drug against a concentration gradient.

Question 5

What is the impact of efflux transporters on drug absorption from the small intestines?

Answer 5

Efflux transporters can efficiently remove drugs that have entered cells through passive diffusion. Therefore efflux transporters would decrease drug absorption.

Question 6

What is the mechanism by which nanoparticles cross biological membranes?

Answer 6

Nanoparticles cross the biological membrane via endocytosis.