PK

Question 1

2 major drug distributing processes

Answer 1

Diffusion (molecule by molecule) and bulk flow transfer.

Question 2

Different mechanisms molecules cross a cell membrane (4)

Answer 2

Direct diffusion —> non polar lipids.
Facilitated diffusion —> ion channels.
Carrier molecules —> amino acids.
Pinocytosis —> cell membrane folds around drug molecule creating a vesicle.

Question 3

Describe first pass metabolism and effect on bioavailability.

Answer 3

Involves GI (first) and liver (portal vein). Enzymes degrade the drug reducing it’s bioavailability.

Question 4

What is biliary secretion and enterohepatic circulation in relation to drug recycling?

Answer 4

A (hydrophilic) drug combines with glucouronides and are secreted into the GIT in bile. Hydrolysis occurs releasing the active drug again. Drug is reabsorbed and cycle repeats. Creates a reservoir of approx. 20% of the drug in the body = prolonged effect.