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medicinal chem > Drugs acting on the adrenergic nervous system > Flashcards

Drugs acting on the adrenergic nervous system Flashcards

1
Q

Adrenergic system makes use of the chemical messengers ______ and ______ .

A

adrenaline, noradrenaline

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2
Q

________ is the neurotransmitter released by the sympathetic nerves which feed smooth muscle and cardiac muscle

A

Noradrenaline

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3
Q

Adrenaline is a hormone released along with noradrenaline from the ___________.

A

adrenal medulla

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4
Q

Adrenaline is a hormone released along with noradrenaline from the ___________.

A

adrenal medulla

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5
Q

When is adrenaline released?

A

during times of danger or stress

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6
Q

Both the α and the β-adrenoceptors are what type of receptors?

A

G-protein-coupled receptors

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7
Q

Adrenergic neurotransmission is responsible for the body’s sympathetic or parasympathetic response?

A

sympathetic

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8
Q

The blood vessels supplying skeletal muscle have mainly _______ adrenoceptors and are [constricted/dilated] by adrenaline

A

β2, dilated

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9
Q

What is the function of a1 adrenoreceptors?

A
  1. vasoconstriction
  2. increased peripheral resistance
  3. increased blood pressure
  4. increased closure of internal sphincter of the bladder
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10
Q

What are a2 receptors also called?

A

autoreceptors

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11
Q

What is the function of a2 receptors?

A
  1. inhibition of norepinephrine release
  2. inhibition of acetylcholine release
  3. inhibition of insulin release
  4. lowers sympathetic activity
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12
Q

What is the function of B1 adrenoreceptors?

A
  1. tachycardia
  2. increased lipolysis
  3. increased myocardial contractility
  4. increased release of renin
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13
Q

What is the function of B2 receptors?

A
  1. vasodilation
  2. decreased peripheral resistance
  3. bronchodilation
  4. increased muscle and liver glycogenolysis
  5. increased release of glucagon
  6. relaxed uterine smooth muscle
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14
Q

Both adrenaline and noradrenaline act as?

A

agonists

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15
Q

What is the starting precursor for the synthesis of catecholamines?

A

tyrosine

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16
Q

L-Tyrosine becomes Levodopa by?

A

hydroxylation with tyrosine hydroxylase

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17
Q

Levodopa becomes Dopamine by?

A

decarboxylation with Dopa decarboxylase

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18
Q

What does MAO do?

A

oxidation

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19
Q

What does COMT do?

A

methylation

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20
Q

What happens if reuptake of norepinephrine is prevented?

A

norepinephrine stays longer in the synapse to give a longer duration of adrenergic transmission

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21
Q

How is the excess release of norepinephrine prevented?

A

by inhibiting the a2-receptors using norepinephrine (negative feedback inhibition)

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22
Q

What is isoprenaline?

A

a powerful β-stimulant devoid of α-agonist activity

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23
Q

Norepinephrine is active/inactive, and selective/nonselective

A

active, nonselective

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24
Q

What is the effect of adding isopropyl to noradrenaline?

A
  • increased selectivity for beta receptor because the beta binding site is big enough for isoprenaline
  • decreased activity for alpha receptor
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25
Q

Is alpha or beta receptor bigger?

A

beta receptor

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26
Q

What happens if phenol groups are absent in a compound that binds to B-receptors?

A

activity drops more significantly for β-receptors than for α-receptors

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27
Q

How does the addition of an α-methyl group affect the α2-receptor selectivity?

A

it increases α2-receptor selectivity

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28
Q

Effects of a-Methylnoradrenaline?

A
  • lowers adrenergic transmission

- works similarly to an antagonist but is actually an agonist

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29
Q

What does it mean if we design a compound that selectively activated a2 receptors with minimum activity on other receptors?

A

it means that the compound lowers adrenergic transmission

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30
Q

How is the N-alkyl group affected by a polar functional group such as phenol?

A

the N-alkyl group results in a dramatic rise in activity and selectivity

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31
Q

If we add an extra bulky functionality to any compound, it will become more selective for which receptor?

A

beta receptor

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32
Q

What are the advantages of adding a phenol group to the end of an N-alkyl group?

A
  1. higher beta selectivity
  2. more active because of more hydrogen bonding interactions
  3. higher affinity
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33
Q

Adrenaline is administered with local anaesthetics in order to?

A

to constrict blood vessels and prolong local anaesthetic activity at the site of injection

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34
Q

Why is vasoconstriction important when administering local anaesthetics?

A

because it lowers side effects and prevents the local anesthetic from spreading to other parts of the body

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35
Q

What is ephedrine?

A
  • an adrenergic agonist that activates both α− and β-adrenoceptors
  • natural product existing as a racemate of the R, S and S, R stereoisomers
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36
Q

What is ephedrine used as?

A

a vasopressor and cardiac stimulant

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37
Q

Compare ephedrine to adrenaline

A

it is more lipophilic than adrenaline so it can cross the

blood–brain barrier and act as a stimulant

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38
Q

Why do ephedrine and pseudoephedrine have lower affinity to alpha and beta receptors?

A

because they don’t have catechols; this results in them having less activity

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39
Q

What is Pseudoephedrine?

A
  • adrenergic agonist

- the S,S diastereomer of ephedrine.

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40
Q

What is pseudoephedrine used as?

A

nasal decongestant

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41
Q

Ephedrine and pseudoephedrine are __________ agents.

A

mixed-action adrenergic

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42
Q

What does a mixed-action adrenergic agonist do?

A

it can switch on the alpha and beta receptors

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43
Q

What is dobutamine?

A

β1-agonist

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44
Q

What is dobutamine used for?

A

treatment of cardiogenic shock

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45
Q

What is clonidine?

A

a selective α2-agonist

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46
Q

What is clonidine used for?

A

treatment of hypertension

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47
Q

How does clonidine work?

A

by decreasing the release of norepinephrine

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48
Q

What is oxymetazoline?

A

selective α1-agonist

49
Q

What is xylometazoline?

A

selective α1-agonist

50
Q

Both oxymetazoline and xylometazoline act as?

A

vasoconstrictors

51
Q

Both oxymetazoline and xylometazoline are used in the treatment of?

A

nasal congestion and bloodshot eyes

52
Q

Compare dobutamine to adrenaline/noradrenaline

A

dobutamine is structurally similar to adrenaline/noradrenaline except it has an extension

53
Q

What is phenylephrine?

A

a selective α1-adrenergic receptor agonist

54
Q

What is phenylephrine used as?

A

decongestant

55
Q

What is the consequence of lacking one OH group in the case of phenylephrine?

A

less active, lower affinity

56
Q

What is the difference between phenylephrine and norepinephrine?

A

Phenylephrine has only one OH while norepinephrine has two

57
Q

Isoprenaline shows some selectivity for what receptors?

A

β-receptors (both 1 and 2)

58
Q

What was the disadvantage of using isoprenaline?

A

it showed no selectivity between the different subtypes of β-receptors so it also activated the β1-receptors of the heart, leading to unwanted cardiovascular effects

59
Q

How can selectivity between different types of β-receptors be obtained?

A
  • by introducing alkyl substituents to the side chain linking the aromatic ring and the amine
  • varying the alkyl substituents on the nitrogen
60
Q

What is isoetharine?

A

β2-agonist

61
Q

What is the disadvantage of isoetharine?

A

it was short lasting because the COMT enzyme methylates the catechol and makes it inactive

62
Q

Why is isoetharine more selective for B2?

A

because the ethyl fits a pocket in the binding site of B2 receptor but has no place in the B1 receptor

63
Q

What is salbutamol?

A

β2-agonist

64
Q

Compare salbutamol and isoetharine

A
  • CH2 was added between methyl and OH to make salbutamol to protect it from COMT
  • salbutamol has the same potency as isoprenaline, but is 2000 times less active on the heart and is more selective for B2
65
Q

How long is the duration of action of salbutamol?

A

4 hours

66
Q

Is salbutamol taken up by transport proteins or metabolized by COMT?

A

no

67
Q

Which enantiomer of salbutamol is more active?

A

R enantiomer

68
Q

What is levalbuterol?

A

the pure R enantiomer of salbutamol

B2 agonist

69
Q

Can COMT methylate R-Salbutamol?

A

no because it is not a catechol anymore

70
Q

What is salmefamol?

A

B2 agonist

71
Q

Compare salmefamol to salbutamol

A

salmefamol is 1.5 times more active than salbutamol and has a longer duration of action (6 hours)

72
Q

Advantages of R-Salmefamol extension

A
  • more hydrogen bonding
  • higher affinity
  • higher lipophilicity
73
Q

Why does salmefamol have a longer duration of action?

A

it is more lipophilic so it binds more strongly with albumin in plasma

74
Q

What is the duration of action of salmefamol?

A

6 hours

75
Q

Is salmefamol or salbutamol more suitable for treating noctural asthma?

A

neither

76
Q

What is salmeterol?

A

B2 agonist that has twice the potency of salbutamol and an extended action

77
Q

What is the duration of action of salmeterol?

A

12 hours

78
Q

R-Salmeterol is a bioisostere for?

A

catechol

79
Q

Is R-Salmeterol a COMT substrate?

A

no

80
Q

What is the most important use for a1?

A

nasal decongestion by vasoconstriction

81
Q

What is a2 agonist used for?

A

vasodilation
treatment of hypertension
lowering sympathetic stimulation

82
Q

What is carvedilol?

A

antagonist at both the α and β adrenoceptors

83
Q

What is labetalol?

A

antagonist at both the α and β adrenoceptors

84
Q

What are carvedilol and labetalol both used as?

A

antihypertensives

85
Q

What is carvedilol used for?

A

treatment of cardiac failure

86
Q

What are a1-antagonists used to treat?

A

hypertension or to control urinary output

87
Q

What is prazosin?

A

the first α1-selective antagonist

88
Q

What is the problem with prazosin?

A

it is short acting

89
Q

Why are doxazosin and terazosin better than prazosin?

A

because they are given as once-daily doses

90
Q

What drugs have been used for the treatment of benign prostatic hyperplasia?

A

doxazosin and terazosin

91
Q

______ are being considered as antidepressants

A

α2–antagonists

92
Q

What is mirtazepine?

A

α2–antagonist

antidepressant agent which increases noradrenaline and serotonin levels

93
Q

What was chosen as the lead compound to design β-blockers?

A

isoprenaline

94
Q

What is pronethalol?

A

β-blocker that is a partial agonist

95
Q

What was the first β-blocker to be used clinically for angina, arrhythmia, and high blood pressure?

A

pronethalol

96
Q

What is propranolol?

A

pure β-antagonist

97
Q

What has greater activity - pronethalol or propranolol?

A

propranolol

98
Q

What has greater activity - pronethalol or propranolol?

A

propranolol

99
Q

Which enantiomer of propranolol is the active form?

A

S-enantiomer although propranolol is used clinically as a racemate

100
Q

What is the importance of having an isopropyl?

A

increased B-receptor selectivity

101
Q

What is the first non-selective β-antagonist?

A

propranolol

102
Q

All B1 selective substituents are on ______ position.

A

para

103
Q

What is more potent, practolol or propranolol?

A

propranolol

104
Q

What is more potent, practolol or propranolol?

A

propranolol

105
Q

What is practolol?

A

a selective cardiac β1-antagonist which does not block vascular or bronchial β2 -receptors

106
Q

Why is practolol much safer than propranolol for asthmatic patients?

A

because it is more polar and has fewer CNS effects

107
Q

All second-generation beta blockers are?

A

hydrogen bond acceptors

108
Q

Are first generation beta blockers selective?

A

no

109
Q

Are second generation beta blockers selective?

A

yes

110
Q

What is esmolol?

A

second generation B-blocker that has rapid onset of action

111
Q

Why is esmolol short-acting?

A

it contains ester that is easily hydrolyzed

112
Q

What is esmolol used for?

A

it is administered if the heart starts to beat too rapidly, especially during surgical procedures

113
Q

α-methyltyrosine inhibits?

A

tyrosine hydroxylase (regulatory enzyme for catecholamine biosynthesis)

114
Q

_______ is sometimes used clinically to treat tumour cells which overproduce catecholamines (e.g., Pheochromocytoma)

A

α-methyltyrosine

115
Q

____________ are used as a way of downregulating the adrenergic system

A

false transmitters

116
Q

Are false transmitters more or less active than noradrenaline?

A

less

117
Q

Is a-Methylnoradrenaline a neurotransmitter?

A

no

118
Q

__________ was once prescribed as an antihypertensive agent, but it has serious side effects (e.g. depression). Therefore, it is no longer used.

A

reserpine

medicinal chem (3 decks)

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