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Adrenergic Agonists Flashcards

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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 are some of the effects of D1 activation?

A

-Relaxes renal and splanchnic blood vessels

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6
Q

What are some of the effects of D2 activation?

A

-Inhibits adenylyl cyclase

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7
Q

What is the mechanism for a1?

A

Positive coupling of phospholipase C

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8
Q

What is the mechanism for a2?

A

Negative coupling of adenylyl cyclase

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9
Q

What is the mechanism for b1?

A

Positive coupling of adenylyl cyclase

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10
Q

What is the mechanism for b2?

A

Positive coupling of adenylyl cyclase

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11
Q

What is the catecholamine structure?

A

Catecholamines contain two hydroxyl groups on a phenyl ring.

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12
Q

What is the most effective agonist on the alpha receptors?

A

Epinephrine

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13
Q

What is the most effective agonist on the beta receptors?

A

Isoproterenol

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14
Q

What has the greatest effect on diastolic pressure?

A

TPR

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15
Q

What has the greatest effect on systolic pressure?

A

CO

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16
Q

What does EPI stimulate?

A

Stimulates α1, α2, β1 and β2 receptors

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17
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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18
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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19
Q

What are the effects of EPI on the lung?

A

β2 receptor - bronchodilation

α1 receptor - decrease in bronchial secretions

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20
Q

EPI indication

A
  • Anaphylaxis
  • Cardiac arrest
  • Bronchospasm
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21
Q

EPI Toxicity

A

Arrhythmia

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22
Q

EPI Contraindications

A

Late term pregnancy

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23
Q

What does NE stimulate?

A

α1, α2 and β1 receptors

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24
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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25
NE indication
Vasodilatory shock
26
What is the effect of NE on the lung?
NE has limited affinity for β2 receptors and so has limited effects on bronchiole smooth muscle.
27
NE Toxicity
Ischemia due to the increase in TPR
28
NE Contraindications
Pre-existing excessive vasoconstriction and ischemia
29
What does DOPA stimulate?
Stimulates D1,D2, β1, α1 and α2
30
What are the effects of DOPA at low dose?
D1: Decreased TPR | β1: Increased CO
31
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
32
DOPA indication
Cardiogenic shock
33
What is an advantage of DOPA?
It has a vasodilatory effect in renal and mesenteric vascular beds
34
DOPA Toxicity at Low and High Doses
Low infusion rates – hypotension | High infusion rates – ischemia
35
DOPA Contraindications
Tachyarrhythmias and ventricular fibrillation
36
What does isoproterenol stimulate?
Stimulates β1 and β2
37
What are the effects of isoproterenol?
Decreased TPR Increased CO Small decrease in MAP
38
Isoproterenol indication
Bradycardia | Heart Block with high TPR
39
Isoproterenol Contraindications
Angina, particularly with arrhythmias
40
Isoproterenol Toxicity
Tachyarrhythmias
41
What happens to the baroreflex with isoproterenol?
It can lead to greatly increased HR due to the decreased MAP
42
What does dobutamine stimulate?
β1 > β2 > α | selective beta-1 agonist
43
What are the effects of dobutamine?
Increased CO
44
Dobutamine indication
Short-term treatment of cardiac insufficiency in CHF Cardiogenic shock Excess β-blockade
45
Dobutamine Toxicity
Hypotension
46
What is special about the β1 effects of dobutamine?
It has greater inotropy than chronotropy due to lack of β2 activation at low doses
47
What are the Direct Acting Sympathomimetics?
EPI NE DOPA
48
What is a Non-selective β-adrenergic Agonist?
Isoproterenol
49
What is a Selective β1-adrenergic receptor Agonist?
Dobutamine
50
What are Selective β2 adrenergic Agonists?
Terbutaline | Albuterol
51
What is a Selective α1-adrenergic Agonist?
Phenylephrine
52
What is a Selective α2-adrenergic Agonist?
Clonidine
53
What does terbutaline/albuterol stimulate?
Selectively activate β2 receptors
54
What are the effects of terbutaline/albuterol?
Bronchodilation Uterine relaxation Both via β2 receptor activation
55
Terbutaline and Albuterol indication
Bronchospasm | Obstructive Airway Disease
56
Terbutaline and Albuterol Toxicity
Tachycardia b􏰃1 Muscle Tremor b􏰃2 Tolerance 􏰃b2
57
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.
58
What does phenylephrine stimulate?
Selective 􏰀a1 receptor agonist
59
What are the effects of phenylephrine?
Increase TPR and MAP Decrease HR (baroreflex) Pupillary dilation Decrease bronchiole and sinus secretions All via a1 agonist
60
Phenylephrine indication
Paroxysmal supraventricular tachycardia Mydriatic agent (dilation of eyes) Nasal decongestant Used for hypotension seen in anesthesia
61
Phenylephrine Toxicity
Hypertension
62
Phenylephrine Contraindications
Pre-existing hypertension | Ventricular tachycardia
63
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.
64
What does clonidine stimulate?
Selective 􏰀a2 adrenergic receptor agonist
65
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.
66
Clonidine indication
Hypertension when cause is due to excess sympathetic drive
67
Clonidine Toxicity
``` Dry mouth Hypertensive crisis (after acute withdrawal) ```
68
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
69
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.
70
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
71
Indirectly acting sympathomimetics indication
Attention Deficit Disorder Narcolepsy Nasal congestion
72
Indirectly acting sympathomimetics Toxicity
Tachycardia
73
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 (74 decks)

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