W3: The concept of drug distribution

Question 1

Definition of drug distribution:

_________ of a drug between ____ , ______ and tissues of the body such as fat and muscle.

Answer 1

Reversible transfer of a drug between the blood and the extravascular fluids and the tissue of body

Question 2

The flow of the drug is from blood -> _________ -> __________ -> cells

Answer 2

blood -> interstitial fluid -> intracellular fluid -> cells

Question 3

Name the 4 water compartments in the body: GO

Answer 3

• plasma
• interstitial fluid
• intracellular fluid
• fat

Question 4

Bound drug molecules = drugs that bind to_____

Answer 4

drugs that bind to plasma proteins

Question 5

Only ____ drugs can move between compartments.

Answer 5

Only free drugs can move

Question 6

so, what the hell is interstitial fluid?

Answer 6

The water/fluid that surround the cell. Its in the extracellular environment.

Question 7

EASY. WHAT IS INTRACELLULAR FLUID?

Answer 7

FLUID INSIDE CELL LAH

Question 8

What two components make up the extracellular fluid (ECF)?

Answer 8

Interstitial fluid and intravascular fluid (plasma)

Question 9

The movement of the drug into the compartments depend on ________ of drug.

Answer 9

Concentration of the drug

Question 10

The drug will be moved back and forth until ________

Answer 10

Equilibrium is achieved

Question 11

Volume of distribution is the

Answer 11

volume into which the drug is distributed to provide the same concentration as it currently is in blood plasma.

Question 12

Small volume of distribution means that the drug would ______________

Answer 12

drug would remain in the systemic circulation

Question 13

Large volume of distribution means that the drug ___________

Answer 13

drug can be found in volumes outside of systemic circulation = widely distributed

Question 14

What contributes to the low Vd for drug?

Answer 14

High degree of plasma protein binding

Question 15

What contributes to the high Vd of a drug?

Answer 15

The drug is most likely highly lipophilic = greater ability to diffuse through membrane

Question 16

Ideally, when a drug has Vd = 40L , it will distribute _____

Answer 16

it will distribute into cells

Question 17

Vd = 3L means ____

Answer 17

drug stays in plasma, bind to plasma protein

Question 18

Vd = 12L means _____

Answer 18

drug stays in extracellular fluid but cannot penetrate cells

Question 19

Vd = >40L means _____

Answer 19

Drug sequestered in extravascular lipid compartment

Question 20

The drug heparin has a Vd= 3L, what does this tell you?

Hint: Distribution, compartment, plasma protein

Answer 20

It remains in only the blood, the systemic circulation, this counts as one compartment.

Heparin binds to plasma protein

Question 21

The drug aminoglycosides has a Vd = 14L, what does this tell you?

(Hint: Distribution, compartment, molecule properties)

Answer 21

The drug can distribute to blood and extracellular fluid (interstitial fluid) = 2 compartments

Drug is hydrophilic and can move through endothelial gap junctions of capillaries.