Receptors: Intro to Pharm

Question 1

What are the principles that are special to and underlie pharmacology?

Answer 1

There are active materials in plants and medicine which cause the effects
Distinct relationship between dose and drug effect
Structure-activity relationship exist
Drugs do not create function they modify it
No drug has a single action

Question 2

Is drugs-receptor binding cause by a single interaction?

Answer 2

Not normally, it is usually a combination of binding interactions which provides forces needed for a drug-receptor complex

Question 3

How does an agonist work?

Answer 3

Binds to the receptor and activate it like a key
Initiates a conformational change in receptor and activation of one or more downstream pathways
Compound that binds to a receptor and produced a biological response

Question 4

How does an antagonist work?

Answer 4

Can fit the lock but can't open it
Drugs that bind to receptors but do not activate it
Inhibit activation by agonists
Block or reverse effects of agonists
No effect on their own

Question 5

What is an allosteric modulator?

Answer 5

Compunds that bind to a seperate site on the receptor from that which normally binds agnoists
Can inc or dec response of natural agonist

Question 6

What is affinity?

Answer 6

Tendency of a drug to complex with a receptor

Question 7

What is the affinity constant?

Answer 7

k(aff) = k1/k2

Value which measures the attraction of a drug for a receptor

Question 8

What is drug selectivity?

Answer 8

Drug must have a molecular conformation which permits binding with a particular receptor surface

Question 9

Potency

Answer 9

The amount of drug necessary to elicit a response
Uses EC50 values
Expressed as the dose of a drug required to achieve 50% of the desired therapeutic effected

Question 10

Analogs of active drugs are sought to be;

Answer 10

More potent, better complete absorption, metabolized less quickly, binds less to plasma proteins and less toxic

Question 11

What are the two types of dose-response curves?

Answer 11

Quantal and grades

Question 12

Quantal dose-response curve

Answer 12

All or none response

Based on population

Question 13

Graded does-response curve

Answer 13

Range of responses

Based on individual

Question 14

Efficacy

Answer 14

The ability of the agonist to cause the receptor to assume an active conformation
Represented by k3
Maximal response a drug can produce

Question 15

What is a partial agonist?

Answer 15

Dual activity as agonists and antagonists
When bound, only partially able to shift the receptor to activated state
Partially inhibits full response at the same receptor

Question 16

What does a spare receptor do?

Answer 16

Makes a tissue more sensitive to an agonist without changing its affinity for the receptor
Maximum response by only occupying a weenie bit of a the receptor

Question 17

What is the therapeutic index?

Answer 17

Measure of drug safety

Question 18

What is the normal therapeutic index?

Answer 18

LD50/ED50

Question 19

What is the more realistic estimate of drug safety based on therapeutic index?

Answer 19

LD1/ED99

Margin of safety

Question 20

What is the protective index of a drug?

Answer 20

ED50/ED50

Undesirable effect/desirable effect

Question 21

Competitive antagonist

Answer 21

Compete with agonist for the same binding site on a give receptor
Makes agonist less potent and shifts the dose response curve right

Question 22

Non-competitive antagonist

Answer 22

Occupy the binding site in an irreversible manner

Question 23

Physiological (functional) antagonism

Answer 23

Response occurs when 2 agonists with opposing effects are administered together

Question 24

What is an example of physiological antagonism?

Answer 24

Histamine (vasodilation) and norepinephrine (vasoconstriction)

Question 25

Competitive antagonism

Answer 25

Response that occurs when a receptor antagonist is administered with an agonist

Question 26

What is an example of competitive antagonism?

Answer 26

Atropine when blocking the effects of acetylcholine (ACh) at a muscarinic receptor

Question 27

Chemical antagonist

Answer 27

Interacts directly with the drug being antagonized to remove it or to prevent it from binding to its target

Question 28

What is an example of a chemical antagonist?

Answer 28

Dimercaprol - a chelator of lead and other toxic metals

Question 29

What is tolerance?

Answer 29

Diminished response to the same dose of a drug over time

Question 30

What are the mechanisms of tolerance?

Answer 30

Desensitization
Down regulation
Tachyphylaxis

Question 31

Desensitization

Answer 31

A rapid process involving continuous exposure to a drug altering the receptor so that it cannot produce a response

Question 32

What is an example of desensitization?

Answer 32

Continuous exposure to beta adrenergic agonist (albuteral for asthma)

Question 33

Down regulation

Answer 33

Decrease in number of receptors cause by high doses of agonists over prolonged periods

Question 34

Tachyphylaxis

Answer 34

Rapid development of tolerance

Indirect-acting amines exert their effect by releasing monoamines

Question 35

What is supersensitivity/hyperactivity?

Answer 35

Enhanced response to a drug that may be due to an increased number of receptors (upreg)
Antagonists or denervation cause up-reg of receptors

Question 36

Potentiation

Answer 36

Enhancement of the effect of one drug by another which has no effect on its own
Produces a parallel shift of the log-dose response curve to the left

Question 37

What is an example of potentiation?

Answer 37

Cocaine potentiates response to noreponephrine

Question 38

Syngergism

Answer 38

Production of a greater response than 2 drugs that act individually

Question 39

What are two types of down regulation?

Answer 39

The cell type specificity of receptor subtypes

The cell type specificity of receptor-effector coupling