Distribution

Question 1

Why is it important that drug in plasma is unbound?

Answer 1

Only unbound (free) drug can cross cellular barriers to access tissues and bind to receptors.

Question 2

Name 3 drug-binding proteins that can be found in the plasma.

Answer 2

1. )Albumin
2. )Lipoproteins
3. )alpha1-acid-glycoprotein

Question 3

What is Fraction unbound (Fu)?

Answer 3

Fu is the amount (conc) of free drug in plasma out out of all of the drug in plasma (free and bound).
Drug conc plasma free / Drug conc plasma total

Question 4

What two physiological factors affect Fu?

Answer 4

1. )The number of protein binding sites available

2. ) The drug’s affinity to the protein

Question 5

What is Bmax?

Answer 5

Bmax is the maximal concentration of protein binding sites. It is proportional to the concentration of protein in the plasma and the number of binding sites on each of these protein molecules.

Question 6

What is Kd?

Answer 6

The concentration of free drug when the concentration of bound drug is 50% of Bmax i.e. at 50% of its binding ability. It represents the drugs affinity for the protein.

Question 7

Name three concepts of reverisble drug binding and equilibrium

Answer 7

1. ) Equilibrium between free drug and bound drug in plasma
2. ) Equilibrium between free drug in plasma and free drug in tissue
3. ) Equilibrium between free drug in tissue and bound drug in tissue