DRUG DISTRIBUTION

Question 1

Describe perfusion rate limited distribution of drug into tissues

Answer 1

drug distribution is limited by blood flow

Question 2

Describe permeability rate limited distribution of drug into tissues

Answer 2

drug distribution is limited by membrane permeability

Question 3

Name the mechanisms of transvascular transport

Answer 3

convection
diffusion

Question 4

Describe transvascular movement via convection

Answer 4

Due to the pressure gradient

Question 5

Describe transvascular movement via diffusion

Answer 5

Primarily due to the concentration gradient

Question 6

Describe how differences in tissue pH may result in the trapping of ionizable drugs

Answer 6

Equilibrium between different compartments (e.g. blood → urine) can be shifted by drug “trapping” due to differences in protonation states in different pH environments

Question 7

Describe how plasma protein binding affects distribution and pharmacologic effect

Answer 7

Since usually only small molecules can cross endothelial membranes, binding of drug to plasma protein or RBC restricts distribution
– A shift in either tissue binding or plasma protein binding can change distribution of a drug.

Question 8

List 4 mechanisms by which drugs may gain access to the CNS

Answer 8

Appropriate physiochemical properties
Utilize an existing transporter
Disruption of the blood brain barrier
Direct administration into the CNS