introduction to drug action

Question 1

What causes receptor occupancy

Answer 1

when a ligand binds to a receptor without causing a tissue response

Question 2

why do drugs need specificity

Answer 2

must act selectively for a specific receptor, otherwise could bind to non-target receptors and cause a response

Question 3

When are there equilibrium when forming the ligand-associated complex

Answer 3

concentration of ligand required to make 50% of the receptors bound, 50% free

Question 4

what is the association (forward) rate constant

Answer 4

k + 1

Question 5

what is the disassociation (backward) rate constant

Answer 5

k-1

Question 6

What type of bonds allow ligands to easy bond/disassociate with receptors

Answer 6

ionic
LdF’s

Question 7

how is a drug determined to have high affinity for a receptor

Answer 7

low concentration required to reach equilibrium between association and disassociation

Question 8

How is the disassociation constant formed

Answer 8

KA = k-1 / k+1

Question 9

What is the disassociation constant used for

Answer 9

to compare drugs affinities for receptors
ensures target receptor only

Question 10

Which equation models the relationship between ligand concentration and receptor occupancy

Answer 10

Hill-Langmuir equation

Question 11

What is KA

Answer 11

the concentration of ligand required to occupy 50% of the receptors

Question 12

How is the KA found using a graph

Answer 12

increase the ligand concentration until fractional occupancy reaches 50%

Question 13

What does a lower KA mean

Answer 13

higher affinity of ligand for receptor

Question 14

what are the 2 ways to compare drug affinity

Answer 14

disassociation constant
radioligand displacement (Ki)

Question 15

what is efficacy

Answer 15

the tendency for an agonist to activate the receptor

Question 16

why can a ligand with affinity for a receptor not activate a tissue response

Answer 16

ligand may bind but be metabolised before causing an effect

Question 17

Why do some agonists only need to occupy a small % of receptors to give a maximal response

Answer 17

signal amplification

Question 18

what is drug potency

Answer 18

the concentration/amount needed to reach EC50

Question 19

what does drug potency depend on

Answer 19

receptor affinity/efficacy
tissue parameters

Question 20

How do partial agonists work

Answer 20

an agonist that will not activate a full tissue response even with 100% receptor occupancy

Question 21

What is the function of a reversible competitive antagonist

Answer 21

competes for binding site
disassociates

Question 22

How can the affects of reversible competitive antagonism be overcome

Answer 22

if agonist concentration is increased

Question 23

what happens to an agonist concentration response curve in the presence of an antagonist

Answer 23

shifts right - higher agonist concentration required for max effect