Drug Distribution

Question 1

What is drug distibution?

Answer 1

• Movement of a drug to/from blood and tissues of the body

- Where does it get to / where doesn’t it

Question 2

What are the factors that effect drug distibution?

Answer 2

• Cardiac Output and blood flow
• Plasma protein binding
• Lipid solubility
• pH of compartments
• Capillary permeability

Question 3

What does the initial rate of distribution heavily depend on?

Answer 3

Cardiac Output and blood flow

Question 4

How potent is albumin?

Answer 4

40g/L

Question 5

What drugs bind to albumin? And where do they bind?

Answer 5

• Lipid soluble drugs (non-specifically)

- Weak acids (specific saturable site)

Question 6

What can cause increased albumin (hyperalbuminemia)?

Answer 6

Dehydration

Question 7

What can cause decreased albumin (hypoalbuminemia)?

Answer 7

• Burns
• Renal diseases
• Hepatic diseases
• Malnutrition

Question 8

How does hyperalbuminemia affect free drug levels?

Answer 8

Decreases free drug levels

Question 9

What lies beneath the basal membrane in the blood brain barrier which adds an extra layer of protection?

Answer 9

Astrocytes

Question 10

Name a disease that can allow drugs to pass more easily through the blood brain barrier

Answer 10

Meningitis

Question 11

What kind of drugs can pass through the placenta and into the foetal circulation?

Answer 11

• Lipid soluble drugs

- Unionised forms of weak acids and bases

Question 12

What other areas have specialised barriers / compartments/

Answer 12

• Placenta
• Chronic abscesses
• Lung infection

Question 13

What is the Volume of water in an average 70 kg adult?

Answer 13

42 litres

Question 14

What is the volume of water in extracellular fluid?

Answer 14

15 litres

Question 15

What is the volmume of water in plasma?

Answer 15

3 litres

Question 16

What is the volume of water in the body that constitutes as intracellular fluid?

Answer 16

27 litres

Question 17

What drugs bind to bone and have a long half-life?

Answer 17

Bisphosphanates

Question 18

What is the volume of distribution?

Answer 18

May be a physiological volume
Theoretical volume that explains where the drug that has been added to a patient has gone
Explains the amount of plasma you need to work out where a drug has gone.

Question 19

How is the apparent volume of distribution calculated?

Answer 19

(Total amount of drug in the body) / (Blood plasma concentration of drug)

Question 20

What is the apparent volume of distribution (Vd)

Answer 20

Vd is the theoretical volume required to account for the amount of drug in the body

Question 21

What does Vd vary with?

Answer 21

• Height
• Weight
• Age
• Fluid accumulation (ascites, oedema, pleural effusion)
• Accumulation of fat

Question 22

When is apparent volume of distribution clinically relevant?

Answer 22

If you want to reach the peak plasma concentration using the bolus of a drug

Question 23

What is the affect of increased volume of distribution of the half-life of a drug?

Answer 23

As volume of distribution increases the half-life of a drug increases