2: pharmacodynamics

Question 1

What is the receptor theory?

Answer 1

drug + receptor -> drug-receptor complex -> effector -> response

Question 2

What is a receptor?

Answer 2

anything of a biological system that reacts w a drug to give an effect

Question 3

what does an agonist do?

Answer 3

interacts with receptor, elicits a direct response

Question 4

what does an antagonist do?

Answer 4

interacts with receptor, does not elicit a direct response

Question 5

What is affinity?

Answer 5

KD. probability that a drug molecule will interact with its receptor to form a DR complex
D + R -> DR
higher affinity -> more DR complex formed
Kd = k2/k1
(k1 is binding, k2 is dissociate)
also half Bmax
smaller kd -> higher affinity -> lower conc of drug needed

Question 6

What is the law of mass action?

Question 7

What is efficacy? what is its value for a full agonist, partial agonist and antagonist?

Answer 7

alpha. a measure of the biological effectiveness of the DR complex
full agonist: a=1
partial agonist: 0<a<1
antagonist: a = 0
higher efficacy -> higher Emax

Question 8

formula for response

Answer 8

a.[DR]

Question 9

pharmacological efficacy vs clinical efficacy vs receptor efficacy

Answer 9

pharmacological efficacy: max response that can be achieved with a drug
clinical efficacy: how well a treatment succeeds in achieving its aim
receptor efficacy: ability to produce an effect on the receptor (agonist has efficacy, antagonist doesnt)

Question 10

drug conc-response relationship

Answer 10

[DR] = [Rt].[D] / (Kd + [D])

Question 11

What is EC50?

Answer 11

dose (conc of drug) to produce 50% of max response
indicates and helps compare potency
lower EC50 -> higher potency

Question 12

properties of dose/drug-response curve

Answer 12

• Emax
  
  • EC50 at 1/2 Emax
  • Sigmoidal (when [D] is logged - ie log[D])

Question 13

What is potency? What does a higher/lower EC50 value tell you about its potency?

Answer 13

dose required to produce a given degree of response
lower dose required -> higher potency
lower EC50 -> higher potency

Question 14

why are there spare receptors?

Answer 14

when there is maximum response before all the receptors are occupied
- drug does not need to bind to all receptors to reach max response

Question 15

What is the relationship between receptor density and potency?

Answer 15

more receptors -> increased [DR] -> an apparent increase in drug
[DR] = [Rt].[D] / (Kd + [D])

Question 16

What are the different types of antagonism?

Answer 16

Chemical: does not interact with receptor, cancels each other out by interacting with each other
Pharmacological: receptor level
- competitive: reversible, can be displaced (by increasing conc of agonist)
- noncompetitive: irreversible
Physiological: both targets receptor but each effect cancels each other out

Question 17

how does a competitive antagonist change the log-dose response curve

Answer 17

• shifted to the right (higher [D] needed to reach Emax)
• same Emax
• EC50 increases

Question 18

how does a non-competitive antagonist change the log-dose response curve

Answer 18

• shifted downward
• cannot reach Emax
• EC50 remains

Question 19

What is a graded response?

Answer 19

response that varies in magnitude in a dose-dependent manner

Question 20

What is a quantal response?

Answer 20

all or none (yes/no) response. number of subjects responding to the drug