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Pharm 2024 > PPT 9- Adrenergic Agonists > Flashcards

PPT 9- Adrenergic Agonists Flashcards

exam 2

1
Q

Differentiate between direct acting and indirect-acting adrenergic agonists

A

Direct agonist - bind to receptors and illicit response
Indirect agonist - Increase amount of catecholamines in synapse; either facilitating removal or preventing reuptake

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2
Q

What is the structure of catecholamines?

A

Catechol group + amine group
Benzene ring with adjacent hydroxyl groups at positions 3 & 4 (catechol) and an amine group on side chain

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3
Q

How are catecholamines inactivated?

A

In the gut by catechol-O-methyltransferase (COMT) - can’t take epinephrine or NE orally

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4
Q

Why can non-catecholamines be taken orally?

A

Non-catecholamines (ephedrine) not inactivated in gut because they lack catechol hydroxyl group

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5
Q

Changes in the alpha carbon of catecholamines affect the activity of which enzyme?

A

monoamine oxidase (MAO) - prolonged action by blocking oxidation

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6
Q

Changes in the benzene ring of catecholamines affect the activity of which enzyme?

A

catechol-O-methyltransferase (COMT) - greatly reduces potency

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7
Q

List the affinity for binding of epinephrine, NE, and isoproterenol at alpha receptors

A

Epinephrine = Norepinephrine
>Isoproterenol

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8
Q

List the affinity for binding of epinephrine, NE, and isoproterenol at beta receptors

A

Isoproterenol > Epinephrine ≥ Norepinephrine
B1 (heart): Equal affinity for Epi and Norepi
B2 (lungs): Epi > Norepi

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9
Q

Alpha 1 vs alpha 2 effects

A
  • α1: Gq → phospholipase C → increases IP3 and DAG
    • contracts vascular smooth muscle, prostate contraction, heart - increases force of contraction
  • α2: Gi → decreases cAMP
    • inhibited transmitter release at adrenergic and cholinergic nerve terminals
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10
Q

Compare the effects of beta 1, 2, 3

A

Gs - all increase cAMP
- β1: increases force and rate of contraction (heart) and increases renin release (juxtaglomerular cells)
- β2: promotes smooth muscle relaxation at respiratory, uterine, and vascular smooth muscle
- β3: activates lipolysis in fat cells

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11
Q

Describe the mechanism of action for alpha 1 receptors

A
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12
Q

Describe the mechanism of action for G inhibitory vs G stimulatory receptors

A
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13
Q

What are the 3 monoamine transporters?

A
  1. NET: transports back to presynaptic terminal (NE, dopamine)
  2. DAT: dopamine transporter
  3. ST: serotonin transporter
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14
Q

Differentiate the mechanism of actions of amphetamines vs cocaine

A

Amphetamines - increasing NE released
Cocaine - blocking reuptake NE

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15
Q

What effect does D1 receptor have?

A

Dilates renal blood vessels in smooth muscles

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16
Q

Describe what happens in the cardiovascular system after the administration of an alpha-agonist

A
  • Increases vascular resistance/tone
  • HR decreases (indirect effect)
  • BP increases
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17
Q

Describe what happens in the cardiovascular system after the administration of a beta-agonist

A
  • Decreases vasculature resistance/tone
  • Increased contractility and HR
  • BP decreases overall
18
Q

Describe what happens in the cardiovascular system after the administration of a mixed agonist

A
  • Mixed vascular resistance
  • Increased contractility and HR
  • Increased BP
19
Q

Describe the effects of epinephrine

A
  • Potent vasoconstrictor
    • α receptors
  • Cardiac stimulant (β1)
    • Positive inotropic (force)
    • Positive chronotropic (rate)
  • β2 activation in some vessels
    • Dilation of skeletal muscle vessels
    • Dilation in bronchioles
20
Q

Describe the effects of norepinephrine

A
  • Effects on α and β1
  • Little effect on β2
  • Results
    • Increase in systolic and diastolic
    • Vagal reflexes overcome chronotropic effects
21
Q

Describe the effects of isoproterenol

A
  • Potent β agonist - vasodilator - heart
  • Little effect on α receptors
  • Results
    • Increase cardiac output
    • Fall in Mean arterial pressure
    • Slight decrease or increase in systolic BP
22
Q

Describe the effects of dopamine

A

Triphasic response:
- Low dose: Activates D1 receptors - vasodilation,
decrease in peripheral resistance
- Higher dose: mimics action of epinephrine; β1 receptors in the heart
- Highest dose: activates alpha, increases BP

23
Q

Describe the effects of dobutamine

A
  • β1 selective agonist
  • Cardiac shock, acute heart failure
24
Q

Define non-catecholamine

A

Not targets for COMT

25
Q

What are the effects of phenylephrine

A
  • Pure α agonist, non-catecholamine
  • Decongestant, raise blood pressure - push blood back into systemic
  • Tetralogy of Fallot
26
Q

What are the 4 issues of the heart in TOF?

A
  1. overarching aorta
  2. pulmonic stenosis
  3. VSD
  4. right ventricular hypertrophy
27
Q

What is Midodrine used for? What receptors is it selective for?

A
  • α1 receptor selective
  • Primarily – postural hypotension (orthostatic)
  • Can cause hypertension in primarily supine patient
28
Q

What is ephedrine used for? How does it work?

A
  • Orally active, OTC
  • Releases stored catecholamines (indirect)
  • Mimics epinephrine (direct)
    • Does cross BBB
  • Nasal decongestant (pseudoephedrine)
29
Q

How do amphetamines work?

A
  • Readily enter CNS
  • Mood elevator, appetite suppressant
30
Q

How does cocaine work?

A

Readily enters CNS - Amphetamine-like effects
Inhibits dopamine reuptake into neurons in the pleasure centers (and addictiveness) of the brain

31
Q

What is tyramine and how does it work?

A
  • Tyrosine by-product, increases PANS
  • High concentrations in fermented foods
  • Indirect action - Releases stored catecholamines
  • Metabolized by MAO
  • MAOIs may increase blood pressure significantly after eating fermented foods (increased NE)
32
Q

What questions should you ask before picking a sympathomimetic?

A
  • Which receptor activation is required?
  • Route of administration?
  • Dosing – monitoring therapeutic response
33
Q

What are the 6 major clinical applications of adrenergic agonists?

A

Hypotension, shock, reduce blood flow, cardiac, respiratory, anaphylaxis

34
Q

What is a pressor agent?

A

Increases blood pressure

35
Q

How are adrenergic agonists used to treat hypotension?

A

Enhance blood flow or pressure (direct acting α agonists - NE, phenylephrine)
- most important thing is to maintain cerebral, renal, and cardiac perfusion

36
Q

What is the treatment for shock?

A

volume replacement (underlying cause) and vasoconstrictors or dilators (depends on if cardiogenic shock of non-MI cause)

37
Q

How are adrenergic agonists used to reduce blood flow? What is the drug target?

A

Hemostasis in surgery
Reduce diffusion of local anesthetics away from the desired site
Reduce mucous membrane congestion
Drug target - α receptor agonist (epinephrine and lidocaine)

38
Q

How are adrenergic agonists used to treat cardiac issues?

A

complete heart block and cardiac arrest (isoproterenol and epinephrine); target vasodilation of coronary arteries

39
Q

How are adrenergic agonists used to treat respiratory issues?

A

Bronchial asthma - β2 selective agonists

40
Q

List the most common toxicities associated with sympathomimetic and the adverse effects

A

Pressor agents
- Elevated blood pressure
- Cerebral hemorrhage
- Pulmonary edema
- Angina
- Cardiac tamponade
- MI

CNS Toxicity
- Catecholamines - rare, but can cross BBB at high levels
- Cocaine - cross BBB
- Convulsions
- Cerebral hemorrhage
- Arrhythmias
- MI

41
Q

What are the two commonly used α2 agonists and how do they work?

A

Clonidine and dexmedetomidine; decrease BP by shutting down NE
Increase firing of vagal nerve - decrease in SV and HR
Decrease firing of sympathetic nerves - vasodilation

Pharm 2024 (28 decks)

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