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BMS 242 Core Physiology and Pharmacology > Antagonists > Flashcards

Antagonists Flashcards

1
Q

What are the 5 categories of antagonist action?

A

chemical, pharmacokinetic, physiological, non-competitive, competitive

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2
Q

Describe chemical antagonism

A

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

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3
Q

How does chemical antagonism cause loss of agonist

A

agonist is chemically altered

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4
Q

Give an example of chemical antagonist use

A

inactivation of heavy metal poison

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5
Q

How is the toxicity of heavy metals reduced

A

addition of a chelating agent

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6
Q

example of chelating agent

A

dimercaprol

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7
Q

Example of heavy metal poisons

A

mercury, lead and cadmium

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8
Q

What is the effect of pharmacokinetic antagonists

A

reduce the amount of drug absorbed, metabolised or excreted

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9
Q

How do pharmacokinetic antagonists decrease drug absorbtion

A

decrease absorption in the GI tract

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10
Q

What is an example of a drug reducing absorption

A

opiates reduce absorption by oral route

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11
Q

How do pharmacokinetic antagonists decrease absorption in the gut

A

inhibit gut motility

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12
Q

What does warfarin do

A

thins blood to prevent risk of strokes and heart attacks

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13
Q

How do pharmacokinetic antagonists change the excretion of an agonist

A

alter protein binding and filtration, alter urine pH and flow

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14
Q

Example of pharmacokinetic antagonist that changes the excretion of an agonist

A

diuretics

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15
Q

Describe physiological antagonism

A

interaction of two drugs with opposing actions in the body

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16
Q

Example of two interacting physiological antagonists

A

noradrenaline, histamine

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17
Q

What does histamine cause

A

vasodilation, lowers arterial pressure

18
Q

What does noradrenaline cause

A

rise in arterial pressure - acts on blood vessels and heart

19
Q

What does non competitive antagonist prevent

A

action of an agonist

20
Q

What does non competitive antagonism block

A

step in process between receptor activation and response

21
Q

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

A

false

22
Q

What is a typical target for anti-hypertensive drugs

A

L type calcium channels

23
Q

Example of a drug that targets L type calcium channels

A

Nifedipine

24
Q

What is the effect of blocking L type calcium channels

A

reduces calcium signals, reduces muscle contraction

25
Q

What works at the same site as the agonist

A

competitive antagonists

26
Q

How can competitive antagonist effects be overcome

A

raising concentration of agonist

27
Q

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

A

shifts the curve to the right, is parallel

28
Q

What is the dose ratio

A

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

29
Q

What does the dose ratio give a measure of

A

shift of the dose response curve for given concentration of antagonist

30
Q

What does the Schild analysis look at

A

relationship between dose ratio and concentration of antagonist added

31
Q

What can Schild analysis be used to calculate

A

competitive antagonists affinity

32
Q

Describe the relationship between pA2 value and affinity

A

higher the pA2 value the higher the affinity

33
Q

Describe irreversible competitive antagonism

A

antagonism that cannot be reverse by washing the tissue

34
Q

True or False - irreversible antagonism is time dependent

A

true

35
Q

Example of an irreversible competitive antagonist

A

dibenamine

36
Q

What is dibenamine

A

alkylating drug

37
Q

What is desensitisation

A

effect of drug declines over time when given continuously or repeatedly

38
Q

What are the physiological changes that can lead to desensitisation

A

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

39
Q

What happens if you give frequent doses of salbutamol

A

B2 adrenoreceptors become phosphorylated - signalling shuts down

40
Q

How are receptors lost from cell surface

A

receptors can be internalised

41
Q

What can physiological adaptation occur in response to

A

thiazide diuretics

42
Q

What receptors can be internalised

A

AMPA receptors, opiate receptors

BMS 242 Core Physiology and Pharmacology (13 decks)

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