Pharmacodynamics

Question 1

What is pharmacodynamics?

Answer 1

What the drug does to the body

Question 2

What is a ligand?

Answer 2

Molecule that binds specifically to a receptor

Question 3

What is an agonist?

Answer 3

Molecule that activates a receptor

Question 4

What is an antagonist?

Answer 4

Molecule that blocks the binding of an endogenous agonist

Question 5

What is affinity?

Answer 5

Measure of ability to bind to a receptor

Question 6

What is intrinsic efficacy?

Answer 6

Measure of receptor activation

Question 7

What is efficacy?

Answer 7

Ability of a ligand to cause a measurable response

Question 8

What is used to determine drug action?

Answer 8

Concentration of drug molecules around receptors (in molarity)

Question 9

What are the features of agonists?

Answer 9

Have intrinsic efficacy
Have efficacy
Have affinity

Question 10

What are the features of antagonists?

Answer 10

Have affinity

No intrinsic efficacy

Question 11

What is Kd?

Answer 11

Dissociation constant

Measure of affinity

Question 12

What does a low Kd mean?

Answer 12

High affinity

Question 13

What does a high Kd mean?

Answer 13

Low affinity

Question 14

What is Bmax?

Answer 14

Maximum biding capacity

Question 15

How is Kd calculated?

Answer 15

Drug concentration at 50% occupancy of receptors

Question 16

What are the usual responses of ligand binding?

Answer 16

Change in signalling pathway

Change in cell/tissue behaviour

Question 17

What is EC50?

Answer 17

Effective concentration giving 50% of maximal response

Question 18

What does EC50 measure?

Answer 18

Agonist potency

Question 19

What does EC50 depend on?

Answer 19

Affinity

Intrinsic efficacy

Question 20

What are spare receptors?

Answer 20

Receptors that exist when a lower % binding can cause a 100% response

Question 21

Why do spare receptors exist?

Answer 21

Amplification in the signal transduction pathway

Response limited by post-receptor event

Question 22

Why do we need spare receptors?

Answer 22

Increase sensitivity

Changing receptor number changes agonist potency

Question 23

What happens to receptor numbers with low activity?

Answer 23

Up-regulation

Question 24

What happens to receptor numbers with high activity?

Answer 24

Down-regulation

Question 25

What is the relationship between Kd and EC50 with a full agonist?

Answer 25

EC50 = Kd

Question 26

What is the relationship between Kd and EC50 with a partial agonist?

Answer 26

EC50 ~ Kd

Question 27

What are the uses of partial agonists?

Answer 27

Can allow a more controlled response Work in the absence/low levels of ligand Can act as antagonist if high levels

Question 28

What are the main types of antagonist?

Answer 28

Reversible competitive antagonism Irreversible competitive antagonism Non-competitive antagonism

Question 29

How does a reversible competitive antagonist work?

Answer 29

Blocks ligand from binding with receptor Greater [antagonist] = greater inhibition

Question 30

How can a reversible competitive antagonist be stopped?

Answer 30

Increase concentration of agonist

Question 31

How does an irreversible competitive antagonist work?

Answer 31

Binds with receptor and dissociates slowly or not at all

Question 32

How do non-competitive antagonists work?

Answer 32

Bind to orthosteric site and change shape of receptor so ligand cannot bind