Basic Principles of Pharmacology

Question 1

How does a drug work

Answer 1

By binding to something (e.g. receptors, enzymes, ion channels or transporters)

Question 2

Define pharmacodynamics

Answer 2

The study of how drugs act on the living body

Question 3

Define agonist

Answer 3

A ligand that binds and induces a response

Question 4

Define full agonist

Answer 4

An agonist that produces a maximal effect. It has high efficacy

Question 5

Define partial agonist

Answer 5

An agonist that produces a submaximal effect. It has an intermediate efficacy

Question 6

What is the difference between a full and partial agonist

Answer 6

A full agonist produces a maximal effect, whilst a partial agonist produces a submaximal effect

Question 7

What shaped dose-response curve does a full agonist give

Answer 7

Sigmoidal (S shaped)

Question 8

What shaped dose-response curve does a partial agonist give

Answer 8

Sigmoidal (S shaped), but more shallow than a full agonist

Question 9

Define a competitive antagonist

Answer 9

A ligand that competes with the agonist to bind to the receptor

Question 10

Define a non-competitive antagonist

Answer 10

A ligand that binds to a site that is not the active site and alters the receptor such that the agonist cannot bind

Question 11

Define a reversible antagonist

Answer 11

An antagonist that can be washed out. Binding is not permanent

Question 12

Define an irreversible antagonist

Answer 12

An antagonist that cannot be washed out. Binding is permanent.

Question 13

What is the dose-response curve for a reversible competitive antagonist

Answer 13

Parallel shift to the right. No change in maximal response

Question 14

What is the dose-response curve for an irreversible competitive antagonist

Answer 14

No shift. Maximal response reduced

Question 15

What is the dose-response curve for a reversible non-competitive antagonist

Answer 15

No shift. Maximal response reduced. No change in EC50 value

Question 16

What is the dose-response curve for an irreversible non-competitive antagonist

Answer 16

No shift. Maximal response reduced. No change in EC50 value. Maintains sigmoidal shape.

Question 17

Define physiological antagonism

Answer 17

A ligand that acts in a different place. Causes a different bodily function to counteract the undesirable one

Question 18

Define chemical antagonism

Answer 18

An antagonist that reduces the concentration of an agonist by forming a chemical complex with it

Question 19

Define pharmacokinetic antagonism

Answer 19

An antagonist that affects absorption, distribution, metabolism or elimination

Question 20

Define affinity

Answer 20

The ability of the drug to bind to the target

Question 21

Define efficacy

Answer 21

The ability of the drug to induce a conformational change (activation)

Question 22

What is the affinity and efficacy of an agonist

Answer 22

Full agonists have high efficacy. Partial agonists have intermediate efficacy

Question 23

What is the affinity and efficacy of an antagonist

Answer 23

They have no efficacy because no response is induced.

Question 24

How does a ligand gated ion channel initiate a biological response

Answer 24

Agonist binding causes a conformational change which causes the ion channel to open

Question 25

Give an example of a ligand gated ion channel

Answer 25

Nicotinic acetylcholine receptor

Question 26

How does a GPCR initiate a biological response

Answer 26

Agonist binding causes stimulation of a secondary messenger signalling cascade

Question 27

How does a receptor tyrosine kinase initiate a biological response

Answer 27

Similar to a GPCR. Except the intracellular domain contains tyrosine kinase

Question 28

How does an intracellular hormone receptor initiate a biological response

Answer 28

Ligand activates transcription factors. Factors regulate gene expression by interacting with specific DNA sequences

Question 29

What are the four key stages of pharmacokinetics

Answer 29

Absorption, Distribution, Metabolism, Excretion

Question 30

Define drug absorption

Answer 30

How a drug enters the blood stream

Question 31

What does drug distribution depend on

Answer 31

Physical and chemical properties of the drug. The drugs ability to penetrate cell membranes

Question 32

Define the first pass effect and its importance

Answer 32

When drugs pass through the liver they tend to be converted to less active alternatives. Most drugs need to be able to be active after the first pass

Question 33

Define EC50 value

Answer 33

The concentration of agonist needed to produce 50% of the maximal response

Question 34

Define IC50 value

Answer 34

The concentration of antagonist needed to inhibit 50% of maximal response

Question 35

Define ED50 value

Answer 35

Minimum dose required to show desired activity in half of the tested population after a specific duration of time

Question 36

Define LD50 value

Answer 36

The dose required to kill half of the members of the tested population (LD = lethal dose)

Question 37

Define therapeutic index

Answer 37

The ratio of ED and LC.

Question 38

What is the importance of the therapeutic index

Answer 38

Defines a useable drug dose which will show activity, but not kill.

Question 39

What are the four stages of a clinical trial

Answer 39

1 - check for safety
2 - check for efficacy
3 - confirm findings in a larger population group
4 - test long-term safety in diverse patient population

Question 40

Define ‘drug’

Answer 40

A substance of known chemical structure, which when administered to a living organism produces a biological effect