Drug-Receptor Interactions

Question 1

What can change the position of a concentration-binding curve?

Answer 1

Nothing

Question 2

What does COX stand for?

Answer 2

Cyclooxygenase

Question 3

What is the effect of aspirin on the COX enzyme?

Answer 3

The COX enzyme is acetylated irreversibly so the inflammation pathway is stopped

Question 4

What kind of inhibitor is ibuprofen on COX enzymes?

Answer 4

Competitive reversible

Question 5

What are the 2 ways drugs can produce side effects?

Answer 5

• Drug good at reaching targets but targets are all over the body
• Drug is bad at hitting its targets and the extra targets it hits produce side effects

Question 6

Why does aspirin produce the side effect of stomach ulcers?

Answer 6

COX enzymes are found in mucosal cells in gut lining aka the drug target is found in the wrong place

Question 7

How are side effects from morphine produced?

Answer 7

Due to the drug hitting other targets

Question 8

Give 5 reasons drugs may show side effects and toxicity

Answer 8

• Drugs are insufficiently selective
• Target sites may be involved in many processes
• Prolonged use of drug may cause changes in structure and function
• Patient variability
• Drug interactions

Question 9

Define pharmacokinetics

Answer 9

The way the body deals with a drug e.g. how it is absorbed

Question 10

Define pharmacodynamics

Answer 10

The effects of the drug on the body

Question 11

Give an example of a drug which acts on ion channels

Answer 11

Tetrodotoxin

Question 12

Give an example of a drug which acts on transporters

Answer 12

Cocaine

Question 13

Give some features of metabotropic eceptors

Answer 13

• Always have multiple subunits which transverse the plasma membrane
• N terminus external, C terminus internal

Question 14

What is an ionotropic receptor?

Answer 14

A receptor that responds to a ligand by opening an ion channel

Question 15

What is a metabotropic receptor?

Answer 15

A type of receptor which acts as a second messenger

Question 16

Do antagonists have efficacy?

Answer 16

No

Question 17

What property is shared by both agonists and antagonists?

Answer 17

Affinity

Question 18

What does K_D represent?

Answer 18

The concentration of drug at which 50% of binding sites are occupied

Question 19

Does a higher K_D mean a higher affinity drug?

Answer 19

No, a lower K_D means a higher affinity drug

Question 20

What 5 conditions are required for the receptor occupancy equation (P) to be valid?

Answer 20

• At equilibrium
• [Drug] at receptors= that applied to system
• 1 drug molecule combines with 1 receptor
• Negligible amount of drug added is bound
• Binding of 1 drug does not affect binding of another

Question 21

What does saturable mean?

Answer 21

At some point all binding sites are filled

Question 22

What is the shape of a concentration-binding curve?

Answer 22

Rectangular Hyperbola

Question 23

Define pharmacological response

Answer 23

The ability of an agonist to produce a pharmacological effect in a cell/tissue

Question 24

What does the halfway point of a functional response curve represent?

Answer 24

EC₅₀

Question 25

What is EC_50?

Answer 25

The concentration of drug which produces half the maximum response the specified drug can provide

Question 26

What does a large gap between response and occupancy curves mean for a drug?

Answer 26

It has a high efficacy, the higher the efficacy the further apart the curves are

Question 27

If receptor number is reduced which direction does the conc-response curve shift?

Answer 27

Right

Question 28

What 3 things affect the position of a concentration-response curve?

Answer 28

* affinity * efficacy * receptor no.

Question 29

Define potency

Answer 29

How much drug is needed to produce a particular response

Question 30

Define partial agonist

Answer 30

A drug which must occupy all receptors to evoke their maximum response (drug whose maximum response is less than the full response the tissue is capable of)

Question 31

Which value of ϵ represents full efficacy?

Answer 31

1

Question 32

Give an example of a partial agonist

Answer 32

Salbutamol

Question 33

Which receptors does salbutamol target?

Answer 33

β2 and β1 receptors

Question 34

Where are: β1 and β2 receptors located?

Answer 34

β1 are found in the heart β2 are found in the lungs

Question 35

What is salbutamol used to treat?

Answer 35

Asthma

Question 36

Why does salbutamol in inhalers only affect the lungs and not the heart?

Answer 36

The heart contains a very small number of β2 receptors which salbutamol acts on, whilst the lungs have many β2 receptors

Question 37

What are the 4 types of drug antagonism?

Answer 37

* Competitive * Non-competitive * Uncompetitive * Physiological

Question 38

What is an uncompetitive antagonist?

Answer 38

When binding of an antagonist occurs to an activated form of the receptor

Question 39

What is a competitive antagonist?

Answer 39

An antagonist that binds reversibly at the agonist recognition site, preventing access of normal ligand

Question 40

What is a non-competitive antagonist?

Answer 40

An antagonist that does not bind at the agonist site but inhibits agonist binding in another way

Question 41

Does the presence of a competitive agonist affect the maximum response achieved by an agonist?

Answer 41

No

Question 42

What is the difference between affinity and efficacy?

Answer 42

Affinity is the ability of a drug to bind to a receptor whereas efficacy is the ability of a drug to evoke a biological response

Question 43

What is receptor reserve?

Answer 43

The proportion of receptors that do not need to be occupied to produce a maximum response

Question 44

A more potent drug will produce a concentration response further left or right?

Answer 44

Left

Question 45

What is an uncompetitive agonist?

Answer 45

When binding occurs to an activated form of the receptor

Question 46

Does a very potent drug have a high or low EC₅₀?

Answer 46

Low

Question 47

What is concentration-ratio?

Answer 47

The concentrations of agonist producing the same response in the absence and presence of antagonist

Question 48

What is the y axis of a schild plot?

Answer 48

log (dose ratio-1)

Question 49

What is the x axis of a schild plot?

Answer 49

log[antagonist]

Question 50

How is K_B calculated from a schild plot?

Answer 50

the inverse log of where the line meets the x axis

Question 51

How is relative potency determined?

Answer 51

* log concentration-response curves for each agonist must be plotted on the same graph * agonists then compared by equipotent molar ratios