1.11 Pharmacodynamics II

Question 1

Define the term Kd and its relevance to affinity

Answer 1

Kd = dissociation constant
- It’s the amount of drug it takes to bind 50% of receptors

Smaller amount of Kd = higher attraction (affinity)

Question 2

Describe the role of drug dose in response

Answer 2

They are dose-dependent

EC50 = concentration of drug to cause 50% of max effect

• Think about potency

Question 3

Differentiate between graded and quantal dose-response curves

Answer 3

Graded response - plots the drug effect vs. concentration
- Uses EC50

Quantal dose-response curve - plots rate of outcome of drug vs. drug concentration
- Uses ED50, TD50, and LD50

Question 4

What are the 2 antagonist classifications

Answer 4

Receptor antagonists

• Active site binding
• Allosteric binding

Nonreceptor antagonists

Question 5

Define intrinsic activity and its relationship to efficacy, antagonists, and partial and full agonists

Answer 5

Intrinsic activity - maximal effect of a drug

Intrinsic activity = efficacy

Full agonists have an intrinsic activity of 1

Partial agonists have intrinsic activity less than 1 and greater than 0

Pure antagonists = no intrinsic activity

Question 6

Define an inverse agonist

Answer 6

Opposite effect of agonist

Question 7

Describe the effects of spare receptors on Kd and EC50

Answer 7

It can reach max effect, even if all receptors aren’t bound

Question 8

Describe the effect of high and low doses of noncompetitive antagonists on the dose-response curve in the presence of spare receptors

Answer 8

High dose of noncompetitive agonist wipes out the needed receptors and there’s a partial agonist with low potency

Low dose has max effect and full agonist

Question 9

Define therapeutic index and its relevance to pharmacotherapy

Answer 9

TI = (TD50)/(ED50) = (Toxic Dose 50)/(Effective dose 50)

The higher the TI, the wider the TW, the safer the drug

Question 10

Most drugs bind via what interactions?

Answer 10

Van der waals

Question 11

Define affinity

Answer 11

Attractiveness of a drug for its receptor

Question 12

The effects of drugs are ___ ___

Answer 12

Dose-dependent

Question 13

ED50

Answer 13

Therapeutic Effect

• Concentration of drug needed to produce a therapeutic effect of 50% of population

Question 14

TD50

Answer 14

Toxic effect

Question 15

LD50

Answer 15

Concentration of drug you see death in 50% of patients

Question 16

What does R* mean?

Answer 16

It is a constitutivelly active

- Drug doesn’t have to be bound to receptor and the receptor is still bound

Question 17

D+R is what type of response

Answer 17

Agonist

Question 18

Within active cite binding in antagonists, it can be reversible and irreversible, describe them.

Answer 18

Reversible = competitive antagonist
- Agonist and antagonist compete at active site of receptor

Irreversible = noncompetitive active site antagonist
- agonist and antagonist are bound at the same time because of covalent bond

Question 19

Within allosteric binding in antagonists, it can be reversible and irreversible, describe them.

Answer 19

Reversible and irreversible = noncompetitive allosteric antagonist
- Agonist only binds to the active site

Question 20

Describe nonreceptor antagonists

Answer 20

Chemical antagonist

• Antagonizes (works against) the situation
• Binds nothing

Physiological antagonist

• The physiologies are antagonists
• Don’t work together b/c receptors and signals work against each other

Question 21

Define potency

Answer 21

Reponse of a drug over a given range of concentrations

Higher EC50 = decreased potency

Question 22

Describe the different types of antagonists

Answer 22

Competitive

• Shifts graph to right
• EC50 gets higher
• Add more drug to block antagonist

Noncompetitive

• Irreversible antagonist
• EC50 doesn’t change
• Max effect changes
• Efficacy changes

Question 23

Define therapeutic window

Answer 23

You have an effect to a drug, but no toxicity or lethality