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Pharmacology > Agonists And Dose Response Curves > Flashcards

Agonists And Dose Response Curves Flashcards

1
Q

What do agonists and receptors form and give example

A

Agonist receptor complexes

Salbutamol and B2

Form camp

Bronchodilation

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2
Q

Why is dosage important in pharmacodynamics

A

Need a certain dose for an effect but also there’s a line between toxicity

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3
Q

What is plotted on a dose response curve

A

Agonist concentration/ dosage

Against response % of the body

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4
Q

What is a GRADED dose response curve

A

Response of a particular system (person or tissue) to an AGONIST CONC

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5
Q

What is a QUANTAL dose response relationship curve

A

Where the response of the population/all tissues included

Plotted against the dosage of AGONIST OR ANTAGONIST CONC

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6
Q

Why is the graph placed on log scale

A

To fit the maximum dosage response relationship

Much higher dose needed

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7
Q

What is the maximum response called regardless of dosage

A

Efficacy / eMAX

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8
Q

What does EC50 mean on a dose response curve

A

The concentration/dose needed to produce a 50% response

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9
Q

What does the lowest point on graph show

A

The threshold dose needed for response

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10
Q

Explain the 2 state hypothesis

A

First state is

Drug + receptor —-> complex

The forward binding to this is K1

Reverse (dissociation of drug to receptor) = K-1

Next state is

AR complex —-> activated

Reverse is inactivion of complex

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11
Q

What does the first state (forming complex) show

A

The occupancy and affinity of the drug and receptor

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12
Q

What does the second stage (activation) show and presume

A

Shows efficacy of the drug to form response

Suggests it’s either in the inactive stage or the active (only 2)

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13
Q

How would you measure specific drug binding to receptors

A

You would measure the max number of drug bound (saturation) - non specific drug binding

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14
Q

What is the max drug binding number called

to determine number of drugs bound - non specific drugs

A

Bmax

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15
Q

What is kD a measure of

A

Affinity

It is the equilibrium dissociation constant

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16
Q

How is the kD measured and what does it tell us (equilibrium dissociation constant)

A

K1 association / k-1 dissociation

The lower the kD = higher affinity

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17
Q

When can kD affinity be equal to EC50

A

It is the same as the EC50 ONLY when response is proportional to occupancy of receptors

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18
Q

Why can kD be used to identify drugs or receptors

A

Because the kD of a drug receptor complex is the same in any tissue and person

19
Q

What is EC50 a better measure of than kD because response isn’t proportional to occupancy

A

Potency

20
Q

What is potency and why is it the same measure as EC50

A

Potency is the dosage/ conc needed to produce an effect

If a drug has a high potency (low EC50) it means they produce a response even at a lower concentration

21
Q

What is potency dependant on

A

Affinity of the drug

Efficacy of the drug (ability to activate)

Receptor density

22
Q

What are spare receptors

A

The fact that the proportion between occupancy and response isn’t linear

Some receptors can produce a higher response even in lower numbers

Spare receptors are ones not needed

23
Q

What is efficacy

A

Ability of an agonist to evoke a response in receptor

Maximum is regardless of the dose given

EMAX = max efficacy

24
Q

What is a full agonist

A

An agonist with high efficacy

They have an incline to the active state despite concentration

25
Q

What is a partial agonist

A

Agonist with lower efficacy showing low response

The equilibrium can’t move into the active state as well even if all receptors occupied

26
Q

What are partial agonists used for and give example

A

They are a therapy drug which are used to stop full stimulation and addiction by have lower response

Eg tamoxifen which binds to oestrogen receptor as a partial agonist to stop breast cancer

27
Q

What is the drug called which helps smoking addiction via partial agonist

A

VARENICLINE - binds to nicotine receptors with lower stimulation as nicotine

28
Q

What did lape et al 2008 find

A

Some receptors can be respond the same to partial and full agonists

Eg glycine and nicotinic ach

They are in a flip state between active and inactive

29
Q

What is the model called that suggested receptors have 4 active states instead of 1

A

Ternary complex model

30
Q

What did the ternary complex model show

A

Receptors can become active without an agonist present and also can become gcpr and active that way

31
Q

What is it called when a receptor becomes active on its own

A

Constitutive activity

32
Q

What are inverse agonists

A

Agonists which have higher affinity for the inactive state of complex (low efficacy)

They turn receptor off

33
Q

Give example of inverse agonist which many antagonists are

A

H2 receptor and cimetidine

34
Q

What did kenakin find about inverse agonists

A

85% of competitive antagonists were actually inverse agonists

35
Q

What are allosteric modulators

A

Drugs which bind to a seperate binding site and increase efficacy / response of the receptor by increasing affinity for agonist

36
Q

How is benzodiazepine an allosteric modulstor

A

It binds onto gaba ion channel and increases affinity for gaba

This increases efficacy
Response is more Cl floods in

Calms anxiety

37
Q

What 2 types of allosteric modulators are there

A

Negative - decrease affinity and efficacy

Positive -

38
Q

Why does deug efficacy decrease with repeat administration

A

receptor desensitised

39
Q

What is another word for drug response diminishing (efficacy)

A

Tachyphylaxis

40
Q

What are major players in tachyphylaxis

A

Gradual change in receptor shape

Receptor internalisation (sequestration)

41
Q

What other things can affect drug efficacy over time

A

Drug metabolism

42
Q

What is the therapeutic index?

A

The window/dosage of the antagonist which has desired effects and isn’t an overdose

43
Q

Why is it good to have a large TI

A

Because it makes it easier to dose it and not overdose eg penecillin has large therapeutic index

Pharmacology (24 decks)

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