PHARM - Pharmacokinetics - Drug Absorption and Distribution - Week 1

Question 1

Define pharmacokinetics.

Answer 1

The process of getting drugs to and from their sites of action.

Question 2

What are 4 key questions that are asked for clinical drug use?

Answer 2

What form is the drug in?
Where do you put it?
How much do you use?
How often do you use it?

Question 3

Define administration.

Answer 3

Giving the drug to a recipient.

Question 4

Define absoprtion.

Answer 4

The drug entering circulation.

Question 5

Define distribution.

Answer 5

The drug spreading throughout the body.

Question 6

Define elimination.

Answer 6

The removal of the drug from the body.

Question 7

Name 4 factors that can influence the choice of route of administration.

Answer 7

Patient convenience - oral/rectal/injection
Cost
Bioavailability
Local vs systemic effect

Question 8

Define local and systemic administration (4).

Answer 8

Local
-drug exerts effect at or near administration site
-access to limited tissue
Systemic
-drug enters the bloodstream
-will access many tissue

Question 9

What limits drug access to tissue with local administration?

Answer 9

Absorption

Question 10

What determines drug access to tissue with systemic administration?

Answer 10

Distribution

Question 11

How can the side effects of a locally administered drug be reduced?

Answer 11

By choosing a concentration so that if a drug is absorbed, it is too low to cause systemic effects.

Question 12

What kind of administration route does not require the drug to be absorbed?

Answer 12

Intravenous injection only. All others require absorption.

Question 13

What is drug distribution driven by?

Answer 13

Circulation

Question 14

Is drug distribution uniform?

Answer 14

No, its rarely uniform.

Question 15

How does drug molecular size affect drug distribution?

Answer 15

Smaller molecules cross the vascular endothelium easier

Question 16

How does a drug’s ability to bind plasma proteins affect drug distribution?

Answer 16

Unbound drugs will cross the vascular endothelium easier.

Question 17

How does a drug’s lipid solubility affect drug distribution?

Answer 17

More lipid solubility will allow wasier easier crossing through cell membranes.

Question 18

What happens when a drug’s lipid solubility is very high?

Answer 18

It will be sequestred in lipids (like adipose tissue).

Question 19

Define volume of distribution.

Answer 19

Volume of body water in which a drug appears to be dissolved in after it has distributed throughout the body.

Question 20

Describe the formula for volume of distribution.

Answer 20

Vd = X / C
X = amount in the body
C = concentration in the plasma
Vd is an apparent volume

Question 21

Describe what happens to drugs with a small Vd vs a high Vd, and what concentration in the plasma would be like.

Answer 21

Small Vd - drug binds to plasma proteins, and plasma concentration is higher.
High Vd - drug binds to tissue/taken up by cells, and concentration in plasma is lower.

Question 22

What does volume of distribution tell you?

Answer 22

How much drug will give a particular concentration of drug in the plasma.

Question 23

Use the formula for volume of distribution to demonstrate how it can be used to calculate a dose of a drug to result in a desired concentration within the body.

Answer 23

X = Vd * C
Therefore, X is the dose of the drug administered via IV to give a desired plasma concentration C.