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Adrenergic Agonists Flashcards

1
Q

What are some of the effects of a1 activation?

A

-Vasoconstriction
-Pupil dilation

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2
Q

What are some of the effects of a2 activation?

A

-Inhibits NT release
-Vasoconstriciton

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3
Q

What are some of the effects of b1 activation?

A

-Stimulates increase in inotropy and chronotropy of the heart

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4
Q

What are some of the effects of b2 activation?

A

-Vasodilation
-Bronchodilation

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5
Q

What is the mechanism for a2?

A

Negative coupling of adenylyl cyclase

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6
Q

What is the mechanism for b1?

A

Positive coupling of adenylyl cyclase

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7
Q

What is the mechanism for b2?

A

Positive coupling of adenylyl cyclase

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8
Q

What is the most effective agonist on the beta receptors?

A

Isoproterenol

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9
Q

What has the greatest effect on diastolic pressure?

A

TPR

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10
Q

What has the greatest effect on systolic pressure?

A

CO

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11
Q

What does EPI stimulate?

A

Stimulates α1, α2, β1 and β2 receptors

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12
Q

What are the effects of EPI at low doses?

A

β2 receptor activation causes peripheral vasodilation, thereby decreasing diastolic BP; β1 receptor activation has positive inotropic and chronotropic effects thereby increasing CO and systolic BP

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13
Q

What are the effects of EPI at high doses?

A

At higher doses (>0.2 μg/kg/min, solid lines) effects of α1 receptor activation predominate:

Producing peripheral vasoconstriction, elevated systolic pressure and elevated diastolic pressure due to increased TPR and increased CO.

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14
Q

What are the effects of EPI on the lung?

A

β2 receptor - bronchodilation
α1 receptor - decrease in bronchial secretions

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15
Q

EPI indication

A

-Anaphylaxis
-Cardiac arrest
-Bronchospasm

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16
Q

EPI Toxicity

A

Arrhythmia

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17
Q

EPI Contraindications

A

Late term pregnancy

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18
Q

What does NE stimulate?

A

α1, α2 and β1 receptors

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19
Q

What are the effects of NE?

A

β1: Increase CO
α1, α2: Increase TPR

Decrease in heart rate due to baroreceptor reflex
Increase in MAP

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20
Q

NE indication

A

Vasodilatory shock

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21
Q

What is the effect of NE on the lung?

A

NE has limited affinity for β2 receptors and so has limited effects on bronchiole smooth muscle.

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22
Q

NE Toxicity

A

Ischemia due to the increase in TPR

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23
Q

NE Contraindications

A

Pre-existing excessive vasoconstriction and ischemia

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24
Q

What does DOPA stimulate?

A

Stimulates D1,D2, β1, α1 and α2

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25
What are the effects of DOPA at low dose?
D1: Decreased TPR β1: Increased CO
26
What are the effects of DOPA at high dose?
Increased MAP Increased TPR β1, α1 and α2 are all activated too and lead to the increased BP
27
DOPA indication
Cardiogenic shock
28
What is an advantage of DOPA?
It has a vasodilatory effect in renal and mesenteric vascular beds
29
DOPA Toxicity at Low and High Doses
Low infusion rates – hypotension High infusion rates – ischemia
30
DOPA Contraindications
Tachyarrhythmias and ventricular fibrillation
31
What does isoproterenol stimulate?
Stimulates β1 and β2
32
What are the effects of isoproterenol?
Decreased TPR Increased CO Small decrease in MAP
33
Isoproterenol indication
Bradycardia Heart Block with high TPR
34
Isoproterenol Contraindications
Angina, particularly with arrhythmias
35
Isoproterenol Toxicity
Tachyarrhythmias
36
What happens to the baroreflex with isoproterenol?
It can lead to greatly increased HR due to the decreased MAP
37
What does dobutamine stimulate?
β1 > β2 > α (selective beta-1 agonist)
38
What are the effects of dobutamine?
Increased CO
39
Dobutamine indication
Short-term treatment of cardiac insufficiency in CHF Cardiogenic shock Excess β-blockade
40
Dobutamine Toxicity
Hypotension
41
What is special about the β1 effects of dobutamine?
It has greater inotropy than chronotropy due to lack of β2 activation at low doses
42
What are the Direct Acting Sympathomimetics?
EPI NE DOPA
43
What is a Non-selective β-adrenergic Agonist?
Isoproterenol
44
What is a Selective β1-adrenergic receptor Agonist?
Dobutamine
45
What are Selective β2 adrenergic Agonists?
Terbutaline Albuterol
46
What is a Selective α1-adrenergic Agonist?
Phenylephrine
47
What is a Selective α2-adrenergic Agonist?
Clonidine
48
What does terbutaline/albuterol stimulate?
Selectively activate β2 receptors
49
What are the effects of terbutaline/albuterol?
Bronchodilation Uterine relaxation Both via β2 receptor activation
50
Terbutaline and Albuterol indication
Bronchospasm Obstructive Airway Disease
51
Terbutaline and Albuterol Toxicity
Tachycardia b􏰃1 Muscle Tremor b􏰃2 Tolerance 􏰃b2
52
How can terbutaline and albuterol lead to muscle tremors?
Activation of β2- receptors expressed on pre-synaptic nerve terminals of cholinergic somatomotor neurons increases release of neurotransmitter. This can lead to muscle tremor, a side effect of β-agonist therapy.
53
What does phenylephrine stimulate?
Selective 􏰀a1 receptor agonist
54
What are the effects of phenylephrine?
Increase TPR and MAP Decrease HR (baroreflex) Pupillary dilation Decrease bronchiole and sinus secretions All via a1 agonist
55
Phenylephrine indication
Paroxysmal supraventricular tachycardia Mydriatic agent (dilation of eyes) Nasal decongestant Used for hypotension seen in anesthesia
56
Phenylephrine Toxicity
Hypertension
57
Phenylephrine Contraindications
Pre-existing hypertension Ventricular tachycardia
58
What is the duration of phenylephrine action?
Phenylephrine is not a catecholamine and therefore is not subject to rapid degradation by COMT. It is metabolized more slowly; therefore it has a much longer duration of action than endogenous catecholamines.
59
What does clonidine stimulate?
Selective 􏰀a2 adrenergic receptor agonist
60
What are the effects of clonidine?
Acute increase in BP (peripheral effect) Reduced BP (central effect) Peripherally, clonidine causes mild vasoconstriction and slight increase in BP, also crosses BBB to cause reduced sympathetic outflow thereby reducing vasoconstriction and BP. The loss of sympathetic activity predominates over the direct vasoconstrictor effects of the drug leading to overall reduction in blood pressure.
61
Clonidine indication
Hypertension when cause is due to excess sympathetic drive
62
Clonidine Toxicity
Dry mouth Hypertensive crisis (after acute withdrawal)
63
How do indirectly acting sympathomimetics work?
Indirect acting sympathomimetic agents increase the concentration of endogenous catecholamines in the synapse and circulation leading to activation of adrenergic receptors. This occurs via either: 1) release of cytoplasmic catecholamines or 2) blockade of re-uptake transporters
64
What do the following stimulate: Amphetamine Methamphetamine Methylphenidate Ephedrine Pseduoephedrine Tyramine?
They stimulate the release of endogenous catecholamines. Amphetamine-like drugs are taken up by re-uptake proteins and subsequently cause reversal of the re-uptake mechanism resulting in release of neurotransmitter in a calcium-independent manner.
65
What are the effects of the indirectly acting sympathomimetics?
Increased TPR and diastolic BP Positive inotropic and chronotropic effects leading to an increased systolic pressure CNS stimulant Probably increased NE Anorexia Possibly increased DA
66
Indirectly acting sympathomimetics indication
Attention Deficit Disorder Narcolepsy Nasal congestion
67
Indirectly acting sympathomimetics Toxicity
Tachycardia
68
Indirectly acting sympathomimetics Contraindications
Rx with MAO inhibitors within previous 2 weeks -This can cause exaggeration of the effect in cases like with tyramine

Pharmacology (5 decks)

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