ICPP Review

Question 1

Drug action/ligands are dependent on the

Answer 1

Concentration of drug molecules around receptors

Question 2

What is a ligand

Answer 2

• A ligand is a substance that can interact with target protein- or receptor
• Ligands usually bind to a specific site on the signalling protein(s)
• Can be endogenous signalling molecules

Question 3

What is an agonist

Answer 3

Substance that binds to a receptor and produces a measurable biological response

Question 4

What is an antagonist

Answer 4

Ligands that have affinity for a receptor or target protein but do not produce a biological response

Blocks the effect of agonist

Question 5

What is affinity

Answer 5

How tightly a molecule is bound to its receptor- strength or avidity

Question 6

What is the measure to define affinity

Answer 6

Kd = dissociation constant

Conc of ligand at which 50% of all available receptors are bound

Question 7

Lower Kd =

Answer 7

Greater affinity

Question 8

Intrinsic efficacy is a term used to describe the ability of a ligand to

Answer 8

Generate the active form of the receptor R

Question 9

What is ligand efficacy

Answer 9

Cause a measurable biological response

Question 10

How do we define agonist potency

Answer 10

Conc of a drug that evokes 50% of its maximal response Emax = EC50

Question 11

What is a partial agonist

Answer 11

Ligands that evoke responses that are lower than the mammal response of a full agonist (have a lower Emax)

Lower intrinsic activity

Question 12

Compared to a full agonist, a partial agonist has

Answer 12

Lower intrinsic efficacy (full agonist generates confirmation of receptor which is really good at activating downstream signals, partial agonist is less good at this)

Question 13

Which drug has the highest intrinsic activity in a graph

Answer 13

Question 14

Which drug has highest potency and affinity in graph

Answer 14

Question 15

Pharmacodynamic principles reflected in Kd and EC50

Answer 15

Signal amplification and spare receptors

Question 16

Which pharmacodynamic principle explains a higher Kd than EC50

Answer 16

Spare receptors

Question 17

3 types of drug antagonism

Answer 17

• Reversible competitive antagonism (the same binding site as the endogenous ligand, interaction is relatively weak)
• Irreversible competitive antagonism (the same binding site as the endogenous ligand, interaction is irreversible and reflects high affinity with very slow dissociation, maybe covalent binding)
• Non competitive antagonism (generally allosteric- can ever work post-receptor)

Question 18

Which organs are most likely to be affected by the major adverse side effects of atenolol (beta blocker for hypertension)

Answer 18

brain, kidneys, GI tract

most severe side effects

Question 19

efficacy definition

Answer 19

E Max = maximal response achievable from a drug within particular system or tissue in body

Question 20

intrinsic efficacy definition

Answer 20

a measure of how effective a drug is in inducing the active conformation of the target protein

Question 21

What is potency

Answer 21

the dose of drug required to produce a specific effect of given intensity (usually EC50)

Question 22

greatest potency and highest affinity will have

Answer 22

lowest efficacy and Kd

Question 23

what does a bioavailability of 0.2 tell you

Answer 23

not much of the oral medication is reaching the systemic circulation. Undergoes a large amount of first pass metabolism

Question 24

what will be the Vd of a lipophilic drug that also binds to muscle proteins

Answer 24

high ask it can enter the fat and muscle compartments