Drug-Receptor Interaction

Question 1

What isa drug defined as?

Answer 1

A substance that acts, often by interaction with regulatory molecules, to stimulate or inhibit normal physiologic processes

Question 2

Drug receptors:

Answer 2

Molecules in which a drug will first interact to eventually induce a response (stimulate or inhibit). Drug receptors are specific and usually include endogenous substance (neurotransmitters, hormones), enzymes, transport proteins, ion channels, etc.

Question 3

Pharmacodynamics:

Answer 3

The study of drugs affecting the body. The does-response relationship and drug receptor interactions for each drug are of particular importance

Question 4

Pharmacokinetics:

Answer 4

The study of the effects of what the body does to a drug. This includes the absorption, distribution and elimination by the organism

Question 5

What is of particular importance when studying pharmacokinetics?

Answer 5

The plasma drug concentration as a function of time

Question 6

What are the four type of drug receptors?

Answer 6

1) Ligand-gated ion channel (cholinergic receptors)

2) G-protein coupled receptors (alpha and beta adrenoreceptors)

3) Enzyme-linked receptors (insulin receptors)

4) Intracellular receptors (steroid receptors)

Question 7

What are the types of drug binding?

Answer 7

Agonist+receptor
Antagonist+receptor
Allosteric activator+receptor
Allosteric inhibitor+ receptor

Question 8

What determines the effect of the drug?

Answer 8

drug classification

Question 9

Affinity?

Answer 9

Tightness of interaction between receptor and drug

Question 10

Efficacy:

Answer 10

The strength or extent of the pharmacological effect of agonist. The maximal effect an agonist can achieve at the highest practical concentration

Question 11

Potency:

Answer 11

The amount of drug needed to produce a given effect

Question 12

What is the difference between potency and efficacy?

Answer 12

Potency is the amount of drug required to reach a desired effect.

Efficacy is the maximal response achieved by a drug at any dose

Question 13

What factors contribute to what the body can do to a drug?

Answer 13

Absorption
Distribution
Metabolism
Excretion

Question 14

What factors contribute to what a drug can do to the body?

Answer 14

Mechanism of action
Therapeutic effects
Toxic effects

Question 15

EC50:

Answer 15

The concentration of drug that produces 50% of maximal effect

Question 16

Kd equation:

Answer 16

Kd=(L)(R)/(LR)

Question 17

Kd:

Answer 17

The equilibrium dissociation constant, represents the concentration of free drug at which half-maximal binding is observed

Question 18

How does Kd relate to affinity?

Answer 18

Inverse relationship:
If the Kd is low= binding affinity is high

If the Kd is high= binding affinity low

Question 19

Assumption for Kd=EC50

Answer 19

1) Magnitude of responses is proportional to number of receptors present

2) Emax only occurs when all receptors are bound

3) Cooperatively does not exist

Question 20

Agonist:

Answer 20

A drug which binds to a receptor and results in a biological response
(Promotes)

Question 21

Antagonist:

Answer 21

A drug which binds to a receptor is not associated with a biological response (inhibit). Will prevent an agonist from binding to the receptor

Question 22

What are agonist classified as?

Answer 22

Full agonist= maximal efficacy

Partial agonist=efficacy; greater than baseline but less than full (Ra)

Inverse agonists= efficacy less than baseline (Ri)

Question 23

Partial agonist:

Answer 23

Displaces the full agonist from the receptor. The response is reduced-the partial agonist will act like an antagonist

Question 24

What happens when an antagonist is added to an agonist in the presence of a spare receptors?

Answer 24

EC50 will increase but will not have an overall increase on the agonist EC50 threshold despite the addition of antagonist. Leads to maximal activity with minimal binding

Question 25

Types of antagonist:

Answer 25

Competitive
Noncompetitive
Allosteric

Question 26

Competitive antagonist:

Answer 26

Antagonist binds to the same site as an agonist in a reversible manner

Question 27

Noncompetitive antagonist:

Answer 27

Antagonist binds to the same site as agonist, irreversibly

Question 28

Allosteric antagonist:

Answer 28

Antagonist and agonist bind to different sites on same receptor

Question 29

T/F: Agonist potency will decrease in the presence of a competitive antagonist

Answer 29

True

Question 30

T/F: Maximum efficacy changes in the presence of a competitive antagonist

Answer 30

False. Maximum efficacy remains unchanged in the presence of a competitive antagonist

Question 31

T/F: Antagonist are inhibitors of potency and/or efficacy

Answer 31

True.

Question 32

T/F: Maximum efficacy of an agonist is reduced with a non-compettive antagonist

Answer 32

True.

Question 33

Noncompetitive antagonist:

Answer 33

Allosteric or irreversibly competitive. Will form a covalent bond with the receptor.
Kd= Very low
Decreases efficacy

Question 34

Reduced responsivity:

Answer 34

Chronic use of an agonist can result in the receptor-effector system becoming less responsive.

I.e. alpha-adrenoceptor agents used as nasal decongestants

Question 35

Increased responsivity:

Answer 35

Chronic disuse of a receptor-effector system can result in an increased responsiveness upon re-exposure to an agonist

Question 36

Therapeutic window:

Answer 36

The range of concentrations between the minimum effective concentration and the minimum toxic concentration

Question 37

What does it mean for a drug to have a large therapeutic window?

Answer 37

The drug is safer and requires lesser monitoring

Question 38

T/F: Drugs with larger therapeutic index are safer

Answer 38

True

Question 39

T/F: High LD50 and a low ED50 is safer and has a high therapeutic index

Answer 39

True

Question 40

T/F: Drugs with TI< 2.0 require active monitoring

Answer 40

True

Question 41

Drugs with a TI<2.0:

Answer 41

Digoxin
Lithium
Phenytoin
Theophylline
Warfarin