Dose Response Relationship

Question 1

Magnitude of drug effect on a cell depends on?

Answer 1

Receptor sensitivity to the drug.

Drug concentration at receptor site.

This two above depends on;
The dose of administered drug and

Pharmokinetic profile.(ADME)

Question 2

Graded dose relationship explains what?

Answer 2

It explains that as the drug concentration is increased the pharmacologic effect is increased until all the receptors are occupied.

Question 3

What are the important drug characteristics that can be determined with dose response curve?

Answer 3

Efficacy and potency.

Question 4

What is potency

Answer 4

It’s the amount of drug required to produce an effect.

Question 5

What is EC50

Answer 5

It’s the concentration of drug required to produce half maximum effect

Question 6

How do you know drug A is more potent than drug B?

Answer 6

If drug A has a lesser EC50 than drug B

Question 7

Example of drugs that is used to measure potency

Answer 7

Candersartan and Irbesartan (ARB’s)

Question 8

Which is more therapeutic potent?
Candersartan or Irbesartan

Answer 8

Candersartan is more therapeutic potent.
Requires 4-32mg to produce effect while;

Irbesartan requires about 75-300mg

Question 9

What is efficacy?

Answer 9

It’s the magnitude of response a drug causes when it interacts with a receptor

Question 10

Factors that affect efficacy include?

Answer 10

Number of drug receptor complex.

Intrinsic activity of the drug(i.e ability of a drug to activate a receptor)

Question 11

A drug is said to be Emax when?

Answer 11

All the receptors have been occupied.

Increase in concentration of the drug has no effect here.

Question 12

Does an antagonist have Emax, why?

Answer 12

No?
Because it doesn’t have any effect, so Emax is 0

Question 13

Which is more therapeutic relevant?
Potency or efficacy?

Answer 13

Efficacy, this is because it tells how good a drug is in producing desired effect.

Question 14

What is law of mass action

Answer 14

Principle that the rate of chemical reaction is directly proportional to the concentration of the substance.

Question 15

The quantitative relationship between drug concentration and receptor occupancy respect what law?

Answer 15

The law of mass action

Question 16

What does affinity describe

Answer 16

Strength of binding between ligands and receptor

Question 17

Explain what Kd(affinity) means to be lower or higher.

Answer 17

The higher the Kd value the weaker the interaction btw drugs and receptors.

This is because a greater strength is required for the interaction of receptor with drug.

State the vice versa.

Question 18

What is the explanation to effect of drug concentration to receptor binding

Answer 18

As concentration of free drug increases the ratio of concentration of bound receptors to total receptors approach unity

Question 19

Formula for the effect of drug concentration on receptors

Answer 19

DR/Rt = [D]
———
Kd + [D]

DR: drug receptor complex
Kd: equilibrium constant, measures affinity to receptor.
[D] : free drug concentration

Question 20

What are the assumptions that have to be met for law of mass action to be applied to drug concentration and response;

Answer 20

1) The magnitude of response is proportional to the amount of receptors occupied by the drug.

2) Maximum efficacy occurs when all receptors are bound.

3) one molecule of drug binds to only one molecule of receptor.

Question 21

What is the formula to this assumption;

Answer 21

E/Emax =. [D]
——-
Kd + [D]

Emax: maximum effect of drug
E : effect of drug at concentration [D]

Question 22

What is this assumption trying to tell in summary?

Answer 22

It’s trying to tell that the affinity of drug binding to receptor should be related to the potency of the drug that cause the physiologic effect in a receptor