Drug Absorption LO

Question 1

Name the factors that determine drug absorption across a membrane

Answer 1

1. Characteristics of the membrane
2. mechanisms of passage across membrane
3. dwell time of drug-membrane interface
4. physicochemical characteristics of the drug
5. pH of the microenvironment
6. surface of absorption surface

Question 2

Identify the site in the GI tract where most drug absorption occurs

Answer 2

DA happens most in the small intestine because it has folds of kerckring. The folds greatly increase the surface area for drug absorption. Transit time is 3-5 hours.

Question 3

Describe the mechanisms by which drugs cross biological membranes

Answer 3

Facilitated diffusion & active transport are both examples of carrier-mediated transport. About 95% of drugs are predominantly absorbed by passive transcellular diffusion. Passive transcellular diffusion can be increased by removing charged (ionized) groups, increasing lipophilicity, reducing size

Question 4

Differentiate the two forms of carrier-mediated absorption: facilitated diffusion and active transport

Answer 4

Facilitated diffusion is a type of passive transport that moves molecules or ions across a cell membrane with the help of specific proteins.
Active transport is an energy driven process where membrane proteins transport molecules across cell.

Question 5

Describe the impact of efflux transporter on drug absorption from the small intestine.

Answer 5

Efflux transporter is called the p-glycoprotein. 1. Limited drug absorption 2. Enhanced drug elimination 3. Limited drug distribution

Question 6

Identify the mechanism by which nanoparticles cross biological membranes.

Answer 6

Endocytosis is the process that helps larger particles.