Antagonists

Question 1

What are the 5 categories of antagonist action?

Answer 1

chemical, pharmacokinetic, physiological, non-competitive, competitive

Question 2

Describe chemical antagonism

Answer 2

substances combine in solution so the effects of the active drug is lost

Question 3

How does chemical antagonism cause loss of agonist

Answer 3

agonist is chemically altered

Question 4

Give an example of chemical antagonist use

Answer 4

inactivation of heavy metal poison

Question 5

How is the toxicity of heavy metals reduced

Answer 5

addition of a chelating agent

Question 6

example of chelating agent

Answer 6

dimercaprol

Question 7

Example of heavy metal poisons

Answer 7

mercury, lead and cadmium

Question 8

What is the effect of pharmacokinetic antagonists

Answer 8

reduce the amount of drug absorbed, metabolised or excreted

Question 9

How do pharmacokinetic antagonists decrease drug absorbtion

Answer 9

decrease absorption in the GI tract

Question 10

What is an example of a drug reducing absorption

Answer 10

opiates reduce absorption by oral route

Question 11

How do pharmacokinetic antagonists decrease absorption in the gut

Answer 11

inhibit gut motility

Question 12

What does warfarin do

Answer 12

thins blood to prevent risk of strokes and heart attacks

Question 13

How do pharmacokinetic antagonists change the excretion of an agonist

Answer 13

alter protein binding and filtration, alter urine pH and flow

Question 14

Example of pharmacokinetic antagonist that changes the excretion of an agonist

Answer 14

diuretics

Question 15

Describe physiological antagonism

Answer 15

interaction of two drugs with opposing actions in the body

Question 16

Example of two interacting physiological antagonists

Answer 16

noradrenaline, histamine

Question 17

What does histamine cause

Answer 17

vasodilation, lowers arterial pressure

Question 18

What does noradrenaline cause

Answer 18

rise in arterial pressure - acts on blood vessels and heart

Question 19

What does non competitive antagonist prevent

Answer 19

action of an agonist

Question 20

What does non competitive antagonism block

Answer 20

step in process between receptor activation and response

Question 21

TRUE or FALSE - non competitive antagonists compete with the agonist for the receptor site

Answer 21

false

Question 22

What is a typical target for anti-hypertensive drugs

Answer 22

L type calcium channels

Question 23

Example of a drug that targets L type calcium channels

Answer 23

Nifedipine

Question 24

What is the effect of blocking L type calcium channels

Answer 24

reduces calcium signals, reduces muscle contraction

Question 25

What works at the same site as the agonist

Answer 25

competitive antagonists

Question 26

How can competitive antagonist effects be overcome

Answer 26

raising concentration of agonist

Question 27

Describe the effect of increasing antagonist concentration on competitive antagonist concentration response curve

Answer 27

shifts the curve to the right, is parallel

Question 28

What is the dose ratio

Answer 28

how many more times agonist is needed in the presence of an antagonist

Question 29

What does the dose ratio give a measure of

Answer 29

shift of the dose response curve for given concentration of antagonist

Question 30

What does the Schild analysis look at

Answer 30

relationship between dose ratio and concentration of antagonist added

Question 31

What can Schild analysis be used to calculate

Answer 31

competitive antagonists affinity

Question 32

Describe the relationship between pA2 value and affinity

Answer 32

higher the pA2 value the higher the affinity

Question 33

Describe irreversible competitive antagonism

Answer 33

antagonism that cannot be reverse by washing the tissue

Question 34

True or False - irreversible antagonism is time dependent

Answer 34

true

Question 35

Example of an irreversible competitive antagonist

Answer 35

dibenamine

Question 36

What is dibenamine

Answer 36

alkylating drug

Question 37

What is desensitisation

Answer 37

effect of drug declines over time when given continuously or repeatedly

Question 38

What are the physiological changes that can lead to desensitisation

Answer 38

loss of receptors from cell surface, change in receptor, exhaustion of mediators

Question 39

What happens if you give frequent doses of salbutamol

Answer 39

B2 adrenoreceptors become phosphorylated - signalling shuts down

Question 40

How are receptors lost from cell surface

Answer 40

receptors can be internalised

Question 41

What can physiological adaptation occur in response to

Answer 41

thiazide diuretics

Question 42

What receptors can be internalised

Answer 42

AMPA receptors, opiate receptors