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PA20016 > Drugs acting on adrenoceptors (3) > Flashcards

Drugs acting on adrenoceptors (3) Flashcards

1
Q

What are agonists?

A

Agents that bind to a receptor and elicit a response.

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2
Q

What are the names of the agonists of sympathetic alpha and beta receptors?

A

Sympathetic agonist, adrenergic agonists or sympathomimetic agonists.

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3
Q

What is a sympathomimetic agonist?

A

Agonists that mimic the effects of the sympathetic nervous system.

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4
Q

What are some common catecholamine adrenoceptor agonists?

A

Noradrenaline, adrenaline, dopamine and isoprenaline.

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5
Q

What is significant about noradrenaline and adrenaline?

A

They are non-selective and are naturally occurring.

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6
Q

What is significant about isoprenaline?

A

It is beta selective and synthetic, but does not discriminate against the different types of beta receptors.

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7
Q

What receptors do noradrenaline favour?

A

Alpha - mostly alpha 1.

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8
Q

What receptors does adrenaline favour?

A

Beta over alpha.

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9
Q

What receptor does phenylephrine favour?

A

Alpha 1.

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10
Q

What receptor does clonidine favour?

A

Alpha 2.

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11
Q

What is the function of the alpha 1 receptors?

A

It constricts smooth muscle due to increased calcium levels intracellularly.

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12
Q

What is the function of alpha 2 receptors?

A

In the heart they presynaptically inhibit release as they are coupled with Gi which decreases the amount of cyclic AMP in the nerve terminal.

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13
Q

What is the effect of alpha 1 agonists?

A

Vasoconstrictors - increase blood pressure due to restricted blood flow. They can also be used to prolong the activity of an anaesthetic in the local area.

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14
Q

What is the effect of alpha 2 agonists?

A

They prevent noradrenaline release and therefore reduce blood pressure due to overall reduced sympathetic tone.

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15
Q

What effects does clonidine have and what receptor does it act on?

A

Alpha 2 agonist - central and peripheral effects.

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16
Q

What can adrenaline be used for clinically?

A

Cardiac arrest and anaphylactic shock. This is because blood pressure decreases and the heart struggles to pump blood around the system.

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17
Q

Why can adrenaline be used for cardiac arrest and anaphylactic shock?

A

As beta1 agonists can increase cardiac contractility.

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18
Q

What else can be used to treat cardiogenic shock?

A

Dobutamine.

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19
Q

What is cardiogenic shock?

A

When your heart can’t pump enough blood to meet your body’s needs - it happens in some types of heart attacks.

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20
Q

What is dobutamine more selective at?

A

Beta1 receptors.

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21
Q

What can beta2 agonists be used to treat?

A

Asthma - they relax bronchial smooth muscle.

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22
Q

Give an example of a beta2 agonist.

A

Salbutamol.

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23
Q

What else can beta2 agonists be used in?

A

They increase lean protein mass and lipolysis - there is abuse in the sport and food industry.

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24
Q

If too much beta2 agonist is given to an asthmatic, what may happen?

A

Stimulation of the heart as there are beta2 receptors in the heart as well as the airways.

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25
Q

Where are beta3 receptors found?

A

Adipose tissue.

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26
Q

What is associated with beta3 receptors?

A

Fat breakdown, which is associated with thermogenesis.

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27
Q

What have beta agonists been proposed to be used as?

A

Slimming drugs.

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28
Q

What are the mechanisms in which NA can be removed from the synaptic cleft?

A

Neuronal epinephrine transporter (NET) on the presynaptic membrane, Extraneuronal monoamine transporter (EMT) on the postsynaptic neuron.

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29
Q

What happens after NA has been taken back up into the presynaptic neuron?

A

It is transported actively back into nerve varicosities and VMAT (vesicular monoamine transporter) repackages NA into vesicles.

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30
Q

What happens after NA has been taken into the postsynaptic terminal?

A

It is metabolised by COMT.

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31
Q

How can drugs indirectly act as sympathomimetics?

A

They have similar structures to NA but do not activate receptors - they have other mechanisms that cause amine release.

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32
Q

How can drugs indirectly act to increase NA levels?

A

Substrates for VMAT and NET that cause a rapid increase in cytosolic NA and increase NA in the synapse.

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33
Q

How does amphetamine act to increase NA levels?

A

It reverses NET and VMAT transport.

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34
Q

What can amphetamine be used to treat?

A

Narcolepsy and ADHD.

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35
Q

What can be used as nasal decongestants?

A

Ephedrine, pseudoephredrine.

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36
Q

What is the mechanism of nasal decongestants?

A

They cause vasoconstriction, as in colds there is vasodilation - leaky blood vessels with lots of plasma going into the tissues.

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37
Q

What is the mechanism of cocaine on NA?

A

It inhibits NA to cause an increase of NA in the synapse.

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38
Q

What are some unwanted effects of NA?

A

Hypertension, vasoconstriction, tachycardia, dysrhythmia.

39
Q

What are some unwanted side effects of adrenaline?

A

Same as noradrenaline - hypertension, vasconstriction, tachycardia, dysrhythmia.

40
Q

What are some unwanted effects of isoprenaline?

A

Tachycardia, dysrhythmia.

41
Q

What can isoprenaline be used to treat?

A

Asthma.

42
Q

What are some unwanted side effects of isprenaline?

A

Tachycardia, dysrhythmia.

43
Q

What is dysrhythmia?

A

Abnormality in the rhythm of the heart.

44
Q

What are some unwanted side effects of dobutamine?

A

Dysthythmia.

45
Q

What are some unwanted side effects of salbutamol?

A

Tachycardia, dysrhythmia, tremor.

46
Q

What are some unwanted side effects of phenylephrine?

A

Hypertension, reflex bradycardia.

47
Q

What are some unwanted side effects of clonidine?

A

Drowsiness, oedema.

48
Q

What is the action of tyramine?

A

It releases NA.

49
Q

What is the function of amphetamine?

A

It releases NA from vesicles.

50
Q

What can amphetamine be used for?

A

Narcolepsy, appetite suppressant, drug of abuse.

51
Q

What are some of the unwanted effects of amphetamine?

A

Hypertension, tachycardia, insomnia, psychosis and dependence.

52
Q

What effect does ephedrine have?

A

NA release - beta agonist.

53
Q

What effect does cocaine have?

A

Blocks NET - synaptic NA increase.

54
Q

What is an unwanted effect of cocaine?

A

Hypertension.

55
Q

What is an antagonist?

A

Binds to the receptor but elicits no response - it prevents the binding of an agonist.

56
Q

What is an alpha selective antagonist?

A

Prazosin.

57
Q

What is a beta selective antagonist?

A

Propanolol.

58
Q

How else can NA activity be antagonised?

A

Indirectly by interfering with its synthesis.

59
Q

What effects do alpha adrenoceptor antagonists have?

A

They cause hypotension, postural hypotension due to alpha1 blockade. They increase cardiac output and cause tachycardia. Alpha2 blockage leads to increased sympathetic output.

60
Q

Give examples of alpha adrenoceptor antagonists.

A

Phenoxybenzamine, phentolamine.

61
Q

What is the action of phenoxybenzamine?

A

It is a long lasting alpha adrenoceptor antagonist that is covalently binding. It also blocks other types of receptor such as 5HT, ACh and histamine.

62
Q

How does phentolamine differ from phenoxybenzamine?

A

(both alpha antagonists) - phentolamine is more selective but is shorter acting.

63
Q

What are labetalol and carvedilol?

A

Mixed alpha and beta antagonists that can be used to treat hypertension.

64
Q

-alol at end?

A

Beta blockers.

65
Q

-azosin at end?

A

Selective alpha1 antagonists.

66
Q

What is the effect of selective alpha1 antagonists?

A

Cause vasodilation and a fall in arterial pressure.

67
Q

What are alpha1 antagonists used as clinically?

A

Antihypertensive drugs.

68
Q

Give examples of alpha1 antagonists.

A

Prazosin, doxazosin.

69
Q

What are the benefits of selective alpha 1 antagonists?

A

They cause less tachycardia than non-selective antagonists, but still cause postural hypotension.

70
Q

What else do alpha1 antagonists do?

A

They relax bladder neck smooth muscle and prostate capsule.

71
Q

What can alpha1 antagonists be used to treat?

A

Urinary retention that is associated with prostatic hypertrophy - enlarged prostate.

72
Q

Give an example of an alpha1 antagonist used to treat urinary retention.

A

Tamsulosin.

73
Q

Give examples of selective alpha2 antagonists.

A

Yohimbine and idazoxan.

74
Q

What can yohimbine be used to treat?

A

Male impotence, aphrodisiac and may increase fat burn when combined with exercise. It increases blood flow via vasodilation.

75
Q

What is an aphrodisiac?

A

Increases blood flow - can be used to increase sexual desire.

76
Q

What is phenoxybenzamine?

A

An alpha antagonist and a NET inhibitor.

77
Q

What can phenoxybenzamine be used for?

A

Phaeochromocytoma - tumour of the adrenal tissue.

78
Q

What are some of the adverse effects of phenoxybenzamine?

A

Hypotension, flushing, tachycardia, nasal congestion and impotence.

79
Q

What are some adverse effects of tamsulosin?

A

Failure of ejaculation.

80
Q

What are beta-adrenoceptor antagonists also known as?

A

Beta blockers.

81
Q

What was the first pure antagonist blocking beta1 and beta2 receptors equally?

A

Propranolol.

82
Q

What is a beta1 selective drug?

A

Atenolol.

83
Q

What are the most desired effects of beta antagonists?

A

Effects on the cardiovascular system - they reduce the effect of exercise/excitement such as lowering the oxygen demand on the heart.

84
Q

What effects do beta antagonists have in heart disease?

A

Antidysrhythmic effects - help maintain normal heart rhythm.

85
Q

What other effects do beta antagonists have?

A

Unexpected antihypertensive effects - in hypertensive patients arterial pressure drops over several days. They can also prevent tremor as they are skeletal muscle beta receptors.

86
Q

What are some unwanted effects of beta antagonists?

A

Bronchoconstriction (b2 antagonism), cardiac failure, bradycardia, hypoglycaemia, fatigue, cold extremities, erectile dysfunction and lucid dreams.

87
Q

Why is bronchoconstriction a side effect of beta antagonists?

A

There are some beta1 receptors in the airways, so even selective beta1 antagonists can cause this effect.

88
Q

Why is hypoglycaemia a side effect of beta antagonists?

A

Glucagon release and glycogenolysis is normally stimulated by circulating adrenaline via the b2 receptor, however this is blocked by antagonists.

89
Q

What is hypoglycaemic unawareness?

A

The idea that the symptoms of hypoglycaemia such as tremor and tachycardia are blocked by beta antagonists so the sufferer is unaware of their condition.

90
Q

Why is fatigue a side effect of beta antagonists?

A

There is reduced cardiac output and muscle perfusion during exercise.

91
Q

Why is cold extremities a side effect of beta antagonists?

A

There is a loss of beta 2 induced dilatation of subcutaneous blood vessels.

92
Q

What are some of the clinical uses of beta antagonists?

A

Hypertension, angina, cardiac dysrhythmias, glaucoma, hyperthyroid disease, anxiety, tremor and migraine.

93
Q

What are some common beta antagonists?

A

Propranolol, atenolol, other -olol drugs, timolol.

PA20016 (10 decks)

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