module 8

Question 1

what is the simple occupancy theory?

Answer 1

states 2 things

1. the intensity of a drugs response is proportional to the number of receptors
2. the maximal response occurs when all the receptors (imply that two drugs that act on the same receptor should produce the same effect - drugs have different efficacies so this is NOT true)

Question 2

what is the modified occupancy theory?

Answer 2

1. intensity of drugs response is proportional to the number of receptors occupied

BUT

2. two drugs occupying the same receptor can have different binding strengths (affinity)
3. two drugs occupying the same receptor can have different abilities to activate the receptor

Question 3

how does modified occupancy theory differ from simple theory?

Answer 3

takes into account the affinity of the drug for the receptor and the ability of the drug to activate the receptor

Question 4

what is affinity?

Answer 4

the affinity is the attraction that a drug has for its receptor

Question 5

what are the characteristics of drugs with high affinity?

Answer 5

• highly attracted to their receptor and therefore bind to the receptor effectively even at low concentrations

Question 6

what are the characteristics of drugs with low affinity?

Answer 6

-are weakly attracted to their receptor and therefore bind ineffectively to the receptor even at high concentrations

Question 7

what is the relationship between potency and affinity?

Answer 7

affinity of a drug is the primary determinant of a drugs potency

• drugs with high affinity for their receptor have high potency

-drugs with low affinity for their receptor have low potency

Question 8

what is intrinsic activity?

Answer 8

-ability of a drug to activate the receptor

-drugs have high intrinsic activity cause intense receptor activation

-drugs with low intrinsic activity only minimally activate the idea

Question 9

what is the relationship between intrinsic activity and efficacy?

Answer 9

-the intrinsic activity of a drug is reflected in efficacy

-drugs with high intrinsic activity have high intrinsic activity

-drugs with low intrinsic activity have low maximal efficacy

Question 10

what is an agonist?

Answer 10

molecule that binds to a receptor and activates
mimic actions of endogenous molecules (neurotransmitter and hormones)

Question 11

what is an antagonist?

Answer 11

molecules that bind to a receptor but do not activate it

Question 12

what is a partial antagonist?

Answer 12

molecules that bind to the receptor but have minimal ability to activate it

Question 13

do agonists have intrinsic activity or affinity?

Answer 13

both since theyre able to bind to a receptor and activate the receptor

Question 14

do agonists have intrinsic activity or affinity?

Answer 14

both since theyre able to bind to a receptor and activate the receptor

Question 15

do agonists cause an increased or decreased physiologcial response?

Answer 15

both depending on the receptor activated

Question 16

do antagonists have affinity or intrinsic activity?

Answer 16

have affinity but no intrinsic activity

Question 17

how do antagonists work?

Answer 17

generate effect by preventing binding of other agonist molecules

Question 18

would an antagonist do anything if an agonist werent present?

Answer 18

no - there is no binding to prevent

Question 19

name examples of antagonist drugs

Answer 19

treat OD, betablocker, antihistamine, gastric acid reducer, opioid receptor blockers

Question 20

what is a competitive antagonist?

Answer 20

compete with agonist at same binding site

Question 21

what happens if an competitive antagonist and agonist have the same affinity

Answer 21

drug with higher concentration will bind

Question 22

what is an irreversible antagonist?

Answer 22

binding occurs at the same site as agonist but is irreversible

decreases response of agonist

Question 23

what is an allosteric antagonist?

Answer 23

binding occurs at a different site than the agonist, which changes the conformation of the receptor so the agonist cannot bind there any longer

decrease agonist effects

Question 24

do effects of irreversible antagonists last forever?

Answer 24

no - our body degrades old receptors and makes new ones, so it remains irreversible until replaced (this is why theyre rarely used in therapeutics)

Question 25

are allosteric antagonists competitive or reversible

Answer 25

reversible but not competitive
noncompetitive bcause the agonist and anatagonists bind at different sites

Question 26

what is a partial agonist?

Answer 26

minimal or moderate intrinsic activity
lower maximal efficacy
able to act as an antagonist because it can block a full agonist and only has moderate intrinsic activity

Question 27

what are the 3 types of drug tolerance?

Answer 27

1. desensitization
2. metabolic tolerance
3. tachyphylaxis

Question 28

what is desensitization?

Answer 28

continuous exposure to agonists can cause receptor desensitization - meaning that the receptor is internalized into the cell or destroyed

net effect is decrease in cell surface receptors expression and decreased drug effects

Question 29

what is metabolic tolerance?

Answer 29

continous exposure to drugs results in induction of drug-metabolizing enzyme - results in decrease in the plasma concentration of the drug

Question 30

what is tachyphalaxis?

Answer 30

rapid decrease in the response to a drug
requiring a drug free period to prevent tolerance

Question 31

what is receptor upregulation?

Answer 31

continuous exposure to anatgonist has the opposite effect of tolerance

cell is said to become hypersensitive and occurs because the cell synthesizes more receptors (greater number of receptors at surface means the greater the response)