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Basic Pharmacology > Agonists and dose response curves > Flashcards

Agonists and dose response curves Flashcards

1
Q

Is salbutamol

a) Alpha 2 - adrenoreceptor antagonist
b) beta 2 - adrenoreceptor agonist
c) alpha 1 - adrenoreceptor agonist
d) beta 1 - adrenoreceptor antagonist

A

b

B2 adrenoreceptor agonist

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2
Q

What is the effect of salbutamol?

A

Activates B2 adrenoreceptor = G2 = bronchodilation

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3
Q

Why are concentration response curves semi log?

A

Linear concentration range is too large so x axis is log

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4
Q

0.0001 in log form

A

-4

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5
Q

What is the dose-response relationship when looking at an isolated system?

A

Graded

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6
Q

What is the dose-response relationship when looking at the response of a popualtion?

A

Quantal

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7
Q

Describe the shape of quantal relationship on graph?

A

Upside down U

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8
Q

What 2 values and corresponding characteristics can be determined from % response and log concentration graph?

A 
EC50 = potency
Emax = Efficacy
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9
Q

Drug A has EC50 of 10
Drug B has EC50 of 5
Which has a higher potency?

A

B

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10
Q

Why can affinity not be calculated from % response concentration curve?

A

Affinity needs values for receptor occupancy - y axis would need to be % receptor occupancy

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11
Q

What are the 2 stages of the 2 state hypothesis?

A

Affinity and efficacy

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12
Q

How are affinity and efficacy measured?

A 
Affinity = occupancy
Efficacy = activation
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13
Q

Define affinity

A

Strength a drug binds to receptor

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14
Q

How is affinity calculates?

A

Rate of association/rate of dissociation (k1/K-1)

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15
Q

When a drug has a high affinity how do K1 and K-1 compare?

A

K1 is higher

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16
Q

What is Kd?

A

Equilibrium dissociation constant

17
Q

When does Kd apply?

A

For any given receptor and drug in any tissue as long as the receptor is the same

18
Q

Uses of Kd?

A

Identify unknown receptors, compare affinity fo different drugs on same receptor

19
Q

Assuming there is a linear relationship between receptor occupation and effect how can Kd be calculated?

A

Kd = EC50

20
Q

Kd has an inverse relationship with affinity

How can Kd be calculated?

A

K-1/K1

Rate of dissociation/rate of association

21
Q

Lower Kd has what affect on affinity (and hence probably potency)?

A

Higher

22
Q

What is potency dependent on?

A

Affinity
Efficacy
receptor density
Efficiency of stimulus response mechanism

23
Q

EC50

A

The concentration of drug needed for 50% of maximum response

24
Q

Relationship between EC50 and potency?

A

Lower EC50 = higher potency

25
Q

What does it mean if a system has spare receptors?

A

Receptors can amplify signal so the maximum response is achieved with small receptor occupancy

26
Q

Efficacy definition

A

Ability of agonist to activate receptor

27
Q

What value on dose response curve does efficacy correspond to?

A

Emax

28
Q

Do full or partial agonist have higher efficacy?

A

Full

29
Q

What is full agonist?

What is partial agonist?

A

Max response corresponds to max response a tissue can give

Max response it elicits is lower than max response a tissue can give

30
Q

Why are partial side effects used?

A

Alleviate side effects

31
Q

What are inverse agonists?

A

Agonists that bind receptor and move equilibrium t left to decrease signalling pathways
They have a higher affinity for the inactive complex

32
Q

What are allosteric modulators?

A

Ligands that bind and effect binding of endogenous agonist

33
Q

Difference between positive allosteric modulator (PAM) and negative allosteric modulator (NAM)

A 
PAM = increase affinity/efficacy of endogenous agonist
NAM = decrease affinity/efficacy of endogenous agonist
34
Q

Tachyphylaxis?

A

Desensitisation of receptor due to continued/repeated use

35
Q

What causes desensitisation?

A

Conformational change, internalisation of receptor, altered drug metabolism

36
Q

After tachyphylaxis, if the drug is stopped and started again at another date how does sensitivity change?

A

Increased

Basic Pharmacology (12 decks)

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