Drug Receptor Interactions

Question 1

What is definition of agonist?

Answer 1

A drug that binds to receptor + elicits biological response

Question 2

What is definition of antagonist?

Answer 2

A drug that blocks action of agonist compound by binding to receptor without eliciting a biological response

Question 3

What is definition of affinity?

Answer 3

Ability of drug molecule to bind to receptor site

Question 4

What is definition of efficacy?

Answer 4

Ability of drug to elicit biological response from drug receptor interactions

Question 5

What is definition of partial agonist?

Answer 5

An agonist drug that produces a biological effect but never the maximal of which tissue is capable

Question 6

What is definition of inverse agonist?

Answer 6

An agonist drug that produces an opposing biological response to that observed by full agonist

Question 7

What type of binding is reversible?

Answer 7

H bonding
Ionic bonds
VDWs forces
These are relatively weak, reversible binding dissociation

Question 8

What type of binding is irreversible?

Answer 8

Covalent binding => stable strong bonds , irreversible binding poor dissociation

Question 9

What is Ka?

Answer 9

Amount of drug to occupy 1/2 the number of receptors

Each drug has its own Ka

Question 10

Ka is same as saying …..

Answer 10

Kd

Question 11

Higher the Ka, the …… the affinity

Answer 11

Lower

Question 12

Lower the Ka, the…… the affinity

Answer 12

Higher

Question 13

What occurs in saturation binding experiments?

Answer 13

Need receptor population
Add increasing concentration of agonist
Measure how much the agonist binds to receptor of interest

Question 14

Describe what the Satruation plot graph shows?

Answer 14

There are finite amount of receptor

Bmax=> max amount of receptors which can be bound to drug

Question 15

Describe the experiment to determine efficacy?

Answer 15

Develop assay

Increase concentration of drug

Question 16

What is EC50 mean?

Answer 16

Efficacy
Effective concentration giving 50% biological response which is used to compare drug potency (determined by affinity + efficacy)

Question 17

Affinity (Ka) + efficacy (EC50) are ……..

Answer 17

Not equal
You don’t need full occupancy to give max response
Only small no. Of drug receptor interactions can produce biological effects

Question 18

Describe the characteristics of partial agonists?

Answer 18

Present at receptors -high affinity but less efficacy
Reduces additive highs
Reduces withdrawal effects
Heroin induced highs are reduced in presence of partial agonists

Question 19

What is competitive antagonism?

Answer 19

Receptor only bind either agonist or antagonist
A and Ant compete for same binding site
A and Ant both bind irreversibly
Raising the agonist can store agonist occupancy
This antagonism is said to be surmountable
In presence of Ant conc, the effect of curve is shifted to right
Shift to right is linearly related to [Ant]

Question 20

What is non competitive antagonism?

Give an example

Answer 20

Ant binds to different site from agonist
Leads to conformational changes to active sites which blocks pharmacological effect of agonist
E.g. ketamine

Question 21

What is irreversible antagonism?

Give an example

Answer 21

Ant binds irreversibly to either agonist or non agonist binding sites in receptor through covalent bonds
Reduces number of receptor the agonist can bind to
E.g. aspirin