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ESA 2- Membranes and Receptors > Pharmokinetics 1 > Flashcards

Pharmokinetics 1 Flashcards

1
Q

How do all drugs exert their effects?

A

By binding to a target

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2
Q

What are the majority of drug targets?

A

Proteins, with some exceptions

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3
Q

Give an example of an exception to drug targets being proteins

A

Some antimicrobial and antitumour drugs bind DNA

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4
Q

What do must drugs bind with?

A

Receptors

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5
Q

Is drug binding to receptors reversible?

A

Usually

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6
Q

What is binding of drugs to receptors governed by?

A

Association and dissociation rates

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7
Q

Give 7 targets for drugs

A 
Enzymes
 GPCRs
 Ion channels
 Nuclear hormone receptors
 Integrins
 Other receptors
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8
Q

What % of drug targets are enzymes?

A

47%

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9
Q

What % of drug targets are GPCRs?

A

30%

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10
Q

What % of drug targets are ion channels?

A

7%

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11
Q

What % of drug targets are transporters?

A

4%

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12
Q

What % of drug targets are nuclear hormone receptors?

A

4%

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13
Q

What % of drug targets are other receptors?

A

4%

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14
Q

What % of drug targets are integrins?

A

1%

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15
Q

What is critical in determining drug action?

A

The concentration of drug molecules around receptors

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16
Q

What do drugs of equivalent molar concentrations have?

A

The same concentration of drug molecules

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17
Q

Do drugs of equivalent concentrations by weight have the same concentration of drug molecules?

A

They may not

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18
Q

How much does 1 mole contain?

A

6x10^23

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19
Q

What does 1 molar solution contain?

A

1 mole in 1 litre

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20
Q

How do you calculate grams per litre?

A

Molecular weight x molarity

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21
Q

What do agonists do?

A

Bind to receptors and cause a response

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22
Q

What do agonists have?

A

Both affinity and efficacy

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23
Q

What do antagonists do?

A

Bind to receptors, but do not cause a response

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24
Q

What do antagonists have?

A

Affinity only

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25
Q

What is affinity?

A

The likelihood of a ligand binding to its target

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26
Q

What is efficacy?

A

The likelihood of activation

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27
Q

How is binding information often obtained?

A

By the binding of a radioligand

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28
Q

What is a radioligand?

A

A radioactive version of the ligand

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29
Q

What is Bmax?

A

The maximum binding capacity

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30
Q

What does Bmax give?

A

Information about the number of receptors

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31
Q

What is Kd?

A

The dissociation constant

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32
Q

What is Kd a measure of?

A

Affinity

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33
Q

How is Kd worked out?

A

It is the concentration needed for 50% occupancy

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34
Q

What does a lower Kd value relate to?

A

A higher affinity

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35
Q

On what scale is [drug] usually shown

A

Logarithmic

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36
Q

Where in concentration response curves used?

A

In measured in a response in cells/tissues

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37
Q

When are dose response curve used?

A

When measuring a response in a whole animal

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38
Q

What is Emax?

A

The maximum response

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39
Q

What is EC 50 ?

A

The effective concentration giving 50% of the maximal response

40
Q

What isEC 50 a measure of?

A

Potency

41
Q

What is potency?

A

A combination of both affinity and efficacy

42
Q

What governs potency?

A

The number of receptors

43
Q

In what terms is efficacy measured?

A

Relative- no absolute scale

44
Q

What may agonists with different Emax value have?

A

Different efficancy

45
Q

Do agonists with the same Emax values have identical efficacy?

A

Not always

46
Q

Why may two drugs with the same Emax values not have the same efficacy?

A

They may differ in affinity, meaning that the relationship between occupancy and response will be different- one may be more able to convert binding into function

47
Q

What is the treatment goal is asthma?

A

To activate ß2-adrenoceptors to relax the airways

48
Q

What is the problem with activating ß-adrenoceptors to treat asthma?

A

There are ß-adrenoceptors elsewhere in the body

49
Q

Give an example of where ß-adrenoreceptors are found elsewhere in the body?

A

ß1 in the heart increase the force and rate of contraction

50
Q

What is salbutamol?

A

A ß2-adrenoagonist

51
Q

What is the Kd of salbutamol?

A

20µM for ß1

1µM for ß2

52
Q

What is the result of the lower Kd for ß2?

A

It has a higher affinity

53
Q

Why can salbutamol be used in treatment of asthma?

A

Because of the higher affinity for ß2-receptors, as well as ß2 selective efficacy and route of administration- this limits ß1 activation and side effects

54
Q

What is the route of administration of salbutamol in the treatment of asthma?

A

Oral spray

55
Q

What is salmeterol?

A

A longer acting ß2-adrenagonist than salbutamol

56
Q

How does salmeterol differ from salbutamol?

A

It has no selective efficacy

57
Q

How does salmeterol prevent ß1 activation and side effects?

A

Purely through differences in affinity

58
Q

What is the Kd of salmeterol?

A

1900nm for ß1

0.55nm for ß2

59
Q

What will less than 100% receptor occupancy give in some cases?

A

100% response

60
Q

What is true when 100% receptor occupancy gives 100% response?

A

EC50 is less than Kd

61
Q

Describe the relationship between receptor occupancy and response?

A

Non-linear

62
Q

What is the relationship between receptor occupancy and response influenced by?

A

Both the transduction system/amplification produced by second messengers, and the properties of the tissue

63
Q

What is meant by spare receptors?

A

Some tissues have more receptors than required to produce a maximal response

64
Q

What is the advantage of spare receptors?

A

It increases sensitivity, allowing for responses at low concentrations of agonist

65
Q

What does number of receptors have an effect on?

A

Potency

66
Q

What is a partial agonist?

A

A drug that cannot produce a maximal effect, even with full receptor occupancy

67
Q

How can a partial agonist be identified?

A

By comparing the ability of different agonist to evoke responses in a tissue

68
Q

What is the EC50 of a partial agonist equal to?

A

Its Kd

69
Q

What is the potency of a drug dependent on?

A

Both its affinity and efficacy

70
Q

Are partial agonists more or less potent than full agonists?

A

Can be either

71
Q

Is a partial agonist always so?

A

No

72
Q

What does wether an agonist is partial or not depend on?

A

The tissue and the biological response

73
Q

What are opioids used for?

A

Pain relief Recreationally

74
Q

What can opioid cause?

A

Respiratory depression, leading to death

75
Q

How do opioids act?

A

Primarily through the µ-opioid receptor (GPRC)

76
Q

How do morphine and buprenorphine differ?

A

Morphine is a full agonist of the receptor

Buprenorphine is a partial agonist, with a higher affinity but lower efficacy

77
Q

Why is buprenorphines high affinity and low efficacy advantageous?

A

If it provides adequate pain control it is preferable, as there is less respiratory depression

78
Q

What are the types of antagonist?

A

Reversible competitive
Irreversible competitive
Non-competitive

79
Q

What is the most common form of antagonist?

A

Reversible competitive

80
Q

Where is reversible competitive antagonism important?

A

In therapeutics

81
Q

What does reversible competitive antagonism rely on?

A

A dynamic equilibrium between ligands and receptors

82
Q

What is IC50?

A

The concentration of antagonist giving 50% occupancy

83
Q

How can reversible competitive antagonists be overcome?

A

By high concentrations of agonists

84
Q

Give a therapeutic example of a reversible competitive antagonist?

A

Naloxone

85
Q

What is naloxone?

A

A high affinity, competitive antagonist of µ-opioid receptors

86
Q

What is naloxone used to do?

A

Reverse opioid mediated respiratory depression

87
Q

Why can naloxone be used to reverse opioid mediated respiratory depression?

A

Its high affinity means it will compete effectively with other opioids for receptors

88
Q

When does irreversible competitive antagonism occur?

A

When the antagonist dissociates slowly, or not at all

89
Q

What do irreversible competitive antagonisms cause to the concentration-reponse curve?

A

A permanent shift to the right

90
Q

What do irreversible competitive antagonists do at high concentrations?

A

Suppress the maximal response

91
Q

Why do irreversible competitive antagonists suppress the maximal response at higher concentrations?

A

As spare receptors are filled by the antagonist, not leaving enough receptors free to illicit a maximal response

92
Q

Give a therapeutic example of irreversible competitive antagonism?

A

Phenoxybenzamine

93
Q

What isPhenoxybenzamine?

A

A non-selective irreversible α1-adrenoreceptor blocker

94
Q

Where isPhenoxybenzamine used?

A

In hypertension episodes in pheochromocytoma

95
Q

What is pheochromocytoma?

A

A tumour of the adrenal gland, which causes excessive NA/Adrenaline secretion leading to vasoconstriction

96
Q

What is non-competitive antagonism?

A

The allosteric binding of an antagonist to a receptor (not the ligand binding site)

ESA 2- Membranes and Receptors (13 decks)

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