Lec 3

Question 1

What is pharmacodynamics based on ?

Answer 1

Drug-receptor binding

Question 2

What is needed for a cellular effect to occur?

Answer 2

an adequate number of receptors bound in a cell

Question 3

Does changes in the ON or OFF rate most influence the affinity of a drug

Answer 3

OFF

Question 4

in the (L+R<kon=koff>LR) equation what does each variable stand for?

Answer 4

L= free Ligands
R = proportion of free receptors
Kon = forward or association rate of equation (Kd)
Koff = reverse or dissociation rate of the equation (Kd)
LR = proportion of ligand (L) bound to receptors
Ka = 1/Kd

Question 5

What is the equation for law of mass action?

Answer 5

L x R x Kon = LR x Koff

Question 6

What is the equation for the fraction of all available receptors that are ligand bound?

Answer 6

(LR) / Ro = (L) / Kd+(L)

Question 7

What happens when L = Kd?

Answer 7

then (LR)/Ro = 0.5

Question 8

What is Kd?

Answer 8

The ligand concentration where 50% of receptors are bound by ligand

Question 9

When does maximum ligand receptor binding occur?

Answer 9

When (LR) = Ro or (LR) / Ro = 1.0

Question 10

What does lower Kd mean?

Answer 10

Tighter receptor binding or greater affinity

Question 11

What are the major types of D-R relationships?

Answer 11

Graded and quantal

Question 12

What is a graded D-R relationship?

Answer 12

D-R of an individual

Question 13

What i a quantal relationship?

Answer 13

D-R of a population

Question 14

What is the (DR)/Ro = (D)/Kd+(D) = Effect/max effect equation describing?

Answer 14

The fact that for many drugs, the response (effect) is proportional to the concentration of receptors bound by drug

Question 15

Graded D-R relationship characteristics

Answer 15

Efficency - Emax
Potency- EC50

Question 16

What is EC50

Answer 16

Potency - the drug concentration which elicits 50% of the maximal response (emax) function of affinity and efficacy
Graded D-R

Question 17

What is Emax

Answer 17

Efficacy - maximal response produced by the drug at that receptor
Graded D-R

Question 18

What are quantal D-R plots?

Answer 18

the percentage of the population that responds to a given dose of drug as a function of the drug dose

Question 19

What is TD50

Answer 19

Toxic dose affecting 50% of the pop

Question 20

What is LD50

Answer 20

Lethal dose affecting 50% of pop

Question 21

What is the therapeutic index? (TD50 / ED50)

Answer 21

Gives estimate of relative safety

Question 22

What are agonists?

Answer 22

Drugs that bind a receptor and stabilize it in a particular conformation, usually the active conformation

Question 23

What is *R?

Answer 23

Unbound active receptor

Question 24

What is DR

Answer 24

Bound active receptor

Question 25

How long do *R and DR forms exist

Answer 25

Briefly as they are considered unstable forms

Question 26

Do more potent drugs have greater or lesser affinity for their receptors?

Answer 26

Greater - lower Kd

Question 27

Do more efficacious drugs (larger Emax) have a greater or lesser proportion of their receptors?

Answer 27

Greater

Question 28

What is a full agonist?

Answer 28

capable of eliciting maximal responses at a given receptor