Pharmodynamics I

Question 1

What is the difference between biological receptors and binding sites?

Answer 1

Biological receptors can bind substances AND initiate a subsequent response while binding sites only bind substances.

Question 2

What kind of relationship is there between the fractional occupancy of a drug and the dose?

Answer 2

Non-linear

Question 3

What relationship is there between the response and the dose?

Answer 3

Non-linear

Question 4

What does the occupancy fraction depend upon?

Answer 4

• Affinity

- Concentration (of the dose)

Question 5

Kd

Answer 5

Dissociation constant.

It is the concentration of drug required to bind HALF (50%) of the receptors.

Question 6

What do small Kd values indicate?

Answer 6

High affinity for the receptor

Question 7

ED50

Answer 7

Median effective dose.

The dose required to achieve a QUANTAL effect in 50% of the population.

Question 8

Potency

Answer 8

Concentration necessary to produce 50% of a drug’s max response and is expressed as an EC50 or ED50 value

Question 9

What does the potency of a drug depend on?

Answer 9

• Affinity which is the Kd

- Efficiency of the receptor interaction with the response

Question 10

What does the clinical effectiveness of a drug depend upon?

Answer 10

Emax (maximal efficiency)

Question 11

EC50

Answer 11

Half maximal effective concentration.

Concentration where 50% of its maximal effect is observed (GRADED)

-> Can be quantal, then it is ED50

Question 12

When does EC50 = Kd?

Answer 12

When all spare receptors are bound

Question 13

How does a competitive antagonist change the DR curve?

Answer 13

• Shifts it right
• Increases the ED50
• Emax remains the same

Question 14

How does a non-competitive antagonist change the DR curve?

Answer 14

• Curve does not shift
• ED50 remains the same
• Decrease Emax

Question 15

What happens to the DR curve with more spare receptors?

Answer 15

It gets steeper

Question 16

How does competition with drugs occur?

Answer 16

Dynamic equilibrium is how the competition occurs.

Displacement does NOT occur with drugs on receptor.

Question 17

What is the Fractional Occupancy equation?

Answer 17

F.O. = 1/( 1+(Kd/[D]) )

Question 18

What happens to selectivity as drug dose is increased?

Answer 18

Selectivity will decrease.

Question 19

The Dose-Response Relationship

Answer 19

This is the correspondence between the amount of drug and the magnitude of the effect; increasing the dose, increases the effect in a graded manner.

Question 20

How do Full Agonists affect activity?

Answer 20

Efficacy = 100%

Question 21

How do Partial Agonists affect activity?

Answer 21

Efficacy = 0 - X - 100%

Question 22

How do Neutral Antagonists affect activity?

Answer 22

Efficacy = 0%

Question 23

How do Inverse Antagonists affect activity?

Answer 23

0 > Efficacy

Question 24

How do partial agonists affect the DR curve?

Answer 24

They compete with the normal agonist (drug) and bring the level of response below one.

“One + a half is less than one and a half”

Question 25

Chemical Antagonism

Answer 25

Done via chemical inactivation of a drug

Question 26

Physiologic Antagonism

Answer 26

The use of opposing pathways to antagonize the effects of a drug

Question 27

Biologic Antagonism

Answer 27

One drug may affect the metabolism or pharmacokinetics of another drug

Question 28

What is the quantal DR curve?

Answer 28

The relationship between drug dose and a SPECIFIED effect in a population of individuals

Question 29

TD50

Answer 29

The dose required to get 50% of the population reporting this specific toxic effect

Question 30

LD50

Answer 30

The dose required to achieve 50% mortality from toxicity

Question 31

What is the therapeutic index?

Answer 31

Ratio of the TD50 or LD50 to the ED50

Question 32

What is the therapeutic window?

Answer 32

This is the Dosage Range between the minimum effective therapeutic dose and the minimum toxic dose

Question 33

What is the best assessment of drug toxicity?

Answer 33

Therapeutic window