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Y1 - ICPP > Lecture 17 - Pharmacodynamics > Flashcards

Lecture 17 - Pharmacodynamics Flashcards

1
Q

What is a ligand?

A

Chemical/molecule which binds to a receptor

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2
Q

What happens when a ligand binds to a receptor?

A

Causes conformational change
Signal transduction
Response produced

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3
Q

What type of drug is Salbutamol?

A

B2 selective agonist

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4
Q

What does Salbutamol treat?

A

Asthma

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5
Q

What type of drug is Bisoprolol?

A

B1 selective antagonist

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6
Q

What can Bisoprolol treat?

A

Hypertension
Angina

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7
Q

What type of drug is co-codamol?

A

Mu -opioid receptor agonist

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8
Q

What is co-codamol used for?

A

Analgesic

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9
Q

What type of drug is Atorvastatin?

A

HMG-CoA reductase inhibitor

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10
Q

What is Atorvastatin used to treat?

A

Dyslipidemia

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11
Q

What are the units, Molar, Millimolar, micromolar and nanomolar?

A

mM = 10^-3 0.001M
Micromolar = 10^-6 0.0000001
nM = 10^-9

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12
Q

Why is concentration of drug molecules around receptors critical in determining drug action?

A

Low concentration means receptor less likely to be activated

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13
Q

Do most drugs associate permanently or reversible with receptors?

A

Most bind reversibly

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14
Q

What is an agonist?

A

Ligand that binds to the receptor activating it

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15
Q

What is an antagonist?

A

A ligand/drug that blocks a receptor preventing an agonist binding to the receptor

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16
Q

Agonists and antagonists for receptor have an affinity for that receptor.
What is meant by affinity?

A

The liking/attraction for a ligand to bind to a receptor

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17
Q

What is intrinsic efficacy?

A

Ability for a ligand to change a receptors shape to activate it

(R*) = activated receptor

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18
Q

Describe an agonist in terms of affinity and intrinsic efficacy:

A

Has Affinity for the receptor
Has Intrinsic efficacy (so activates receptor)

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19
Q

Describe an antagonist in terms of affinity and intrinsic efficacy:

A

ONLY has Affinity for receptor
NO INTRINSIC EFFICACY (Doesn’t activate receptor)

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20
Q

What is clinical efficacy?

A

How well a treatment succeeds in completing its aim

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21
Q

What is Efficacy?

A

Takes into account intrinsic efficacy and the things that happen that lead to the desired therapeutic response

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22
Q

What is Bmax?

A

Bmax = Maximum Binding Capacity

When all receptors have ligands bound to them

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23
Q

What is Kd?

A

The concentration of the drug which causes 50% occupancy of ligands bound to receptors
(Conc when 50% of receptors have ligands/drugs bound)

The dissociation constant

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24
Q

What does the value of Kd actually indicate?

A

The affinity/strength of interaction of the ligand and the receptor

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25
Q

If a ligand has a high Kd value what does this indicate?

If a ligand has a low Kd value what does this indicate?

A

High Kd = Low affinity (more drug needed to reach 50% occupancy)

Low Kd = High affinity (less drug needed to reach 50% occupancy)

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26
Q

Why is it useful for drugs to have a high affinity for a receptor? (Low Kd value)

A

Smaller amounts of drugs can be given

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27
Q

What occurs to the respiratory system as a result of a heroin or morphine overdose?

A

Respiratory depression
Then death

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28
Q

How does Naloxone treat a heroin overdose?

A

Antagonist to mu opioid receptor
Naloxone outcompetes the opioid

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29
Q

What must a drug have in order to cause a response when bound to a receptor?

A

Efficacy

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30
Q

What is Emax?

A

The maximum response that can be reached

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31
Q

What is EC50?

A

(Effective concentration giving 50% of maximal response)

The concentration of drug needed to reach 50% of the maximum response

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32
Q

What does the value of EC50 indicate?

A

Drug potency

33
Q

What is Potency?

A

The amount of a drug needed to cause a response (Describes response not binding

34
Q

What does potency depend on?

A

Affinity
Intrinsic efficacy
Cell/tissue-specific component that allow for the response to happen

35
Q

What is concentration of drug at a drug site?

A

When the concentration of a drug at a site of action is KNOWN

36
Q

What is dose of a drug at a drug site?

A

When the concentration of a drug at a site of action is UNKNOWN

37
Q

Give an example of functional antagonism:

A

When treating asthma give a B2 adrenoceptor agonist
This apposes the pathological bronchoconstriction causing smooth muscle to Releaf (bronchodilation)

38
Q

In treating asthma why does the Beta 2 adrenoceptor agonist need to be selective/specific?

A

Don’t want to stimulate B1 adrenoceptors in the heart (unwanted +ve chronotropy, +ve inotropy)

39
Q

Describe the selectivity of Salbutamol for B2 receptors in terms of affinity and efficacy:

A

Has high affinity for B2 receptors
High selective efficacy for B2 compared to B1

Selectivity is based on its B2 selective efficacy

40
Q

Describe the selectivity of Sameterol for B2 receptors in terms of affinity and efficacy:

A

High affinity for B2 receptors

Selectivity based on affinty not selective efficacy

41
Q

Why can Salmeterol not be administered via IV?

A

Insoluble

42
Q

What are spare receptors?

A

When there are receptors that dont additionally contribute to a response

(When the response is limited by other factors)

43
Q

What is the relationship between EC50 and Kd in order for there to be spare receptors?

A

EC50 < Kd

Means that the concentration of the ligand in order to produce the max response is less that the concentration needed to occupy all receptors

44
Q

What causes Spare receptors to exist?

A

Amplification in the signal transduction pathway
Response is limited (muscle can only contract so far)

45
Q

What is the benefit of having spare receptors?

A

Increase sensitivity/potency
Meaning lower concentrations of agonist is required for full response

46
Q

What can receptor number influence?

A

The sensitivity to the agonist
Maximal response (may not be enough receptors for the maximum response to actually be reached)

47
Q

What affects the number of receptors on a cell?

A

Cell type
Increases with low activity (Up regulation)
Decreases with high activity (Down regulation)

48
Q

Why do people need higher doses of morphine the more they have it?

A

The mu opioid receptors become internalised the more they are used (Down regulation)
Means less morphine can bind

49
Q

What is a full agonist?

A

An agonist that will produce a maximum effect/response when theres full occupancy

50
Q

What is a partial agonist?

A

An agonist that is unable to produce a maximum affect even with full occupancy

51
Q

What has a higher potency, a full agonist or partial agonist?

A

Full agonist

52
Q

What is happening in terms of efficacy for partial agonists?

A

Insufficient intrinsic efficacy (LOWER THAN FULL AGONISTS) for maximum response to be reached

53
Q

What is meant be the EC50 for a partial agonist?

A

The concentration of the drug needed to to reach 50% of its response (Not the maximum response)

54
Q

How does a larger response relate to intrinsic activity/efficacy?

A

Larger response = Greater intrinsic activity/efficacy

55
Q

How can you make a partial agonist become a full agonist?

A

Increase the number of receptors

56
Q

How can partial agonists act as drugs?

A

They can act as antagonists by binding to receptors and preventing a full response from occurring (prevent full agonists binding)

57
Q

Heroin is an opioid, what is used to treat a heroin overdose?

A

Buprenorphine

58
Q

How does buprenorphine treat heroin overdose?

A

Is a partial agonist
Binds to mu opioid receptors giving a little high but preventing maximum response preventing RESPIRATORY DEPRESSION and Death

59
Q

How do antagonists generally work?

A

Block effects of agonists be preventing them from binding

60
Q

What are the 3 types of antagonism?

A

Reversible competitive antagonism
Irreversible competitive antagonism
Non-competitive antagonism (usually Allosteric)

61
Q

What is the principle of reversible competitive antagonism?

A

Relies on the antagonist out competing the agonist for the binding site
They do associate and deassociate

62
Q

What is IC50?

A

Inhibitory Concentration 50
The concentration of inhibitor which inhibits 50% of the maximal response

63
Q

What factors affect the inhibition from a reversible competitive antagonist?

A

Antagonists Affinity
Concentration of Antagonist
Concentration of the agonist

64
Q

What can happen if the concentration of the agonist increases but the competitive reversible antagonist does not?

A

Agonist can outcompete the antagonist so the inhibitory effects can be over come

65
Q

What happens to the concentration response curve with a reversible competitive antagonist?

A

Same height shifts to the right

(Maximal response can still be achieved it just happens at a higher concentration of agonist

66
Q

What is a drug which treats heroin OD that is a competitive antagonist?

A

Naloxone

67
Q

What receptors does Naloxone bind to preventing heroin from binding?

A

Mu opioid receptors

68
Q

What is Irreversiible competitive antagonism?

A

When the antagonist dissociates very slowly or not at all

69
Q

Can increasing the [agonist] overcome the effect of irreversible competitive antagonism?

A

No since the receptors all remain blocked

70
Q

How do irreversible competitive antagonists affect the response [agonist] curve?

A

Initially just shift curve further right
Then as [antagonist] increases max response decreases since the spare receptors get inhibited

71
Q

What is Phaeochromocytoma?

A

Tumour of adrenal chromaffin cellls leading to excesss adrenaline/noradrenaline secretion

71
Q

What is Phaeochromocytoma?

A

Tumour of adrenal chromaffin cellls leading to excesss adrenaline/noradrenaline secretion

72
Q

What drug can be given to treat Phaeochromocytoma to act on A1-adrenoceptors?
What drug can be given to treat Phaeochromocytoma to act on B1-adrenoceptors?

A

Phenoxybenzamine
Bisoprolol

73
Q

What does the excess adrenaline acting on A1 adrenoceptors cause?

A

Vasoconstriction
Hypertension
Headache
Sweating
Panic attacks

74
Q

What type of antagonist is clopidogrel?

A

Irreversible competitive antagonist

75
Q

What does clopidogrel do?

A

Reduce platelet activation preventing thrombosis

76
Q

What is non competitive antagonism ?

A

When a ligand binds to a site on the receptor that is not the active site/orthosteric site
This reduces the orthosteric ligands affinity for the active/orthosteric site

77
Q

What is the site called which a non competitive inhibitor will bind to?

A

Allosteric site

78
Q

How can Maraviroc be used with HIV treatment?

A

Binds to receptors Allosteric site
Conformational change of receptor prevents viral ability to bind to receptor
Prevents virus entry into cell

Y1 - ICPP (23 decks)

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