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Pharmacology > Adrenergic Agents (L&J Chp 9) > Flashcards

Adrenergic Agents (L&J Chp 9) Flashcards

1
Q

What are adrenergic agents?

A

Drugs that work on the sympathetic NS

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2
Q

Why do we use adrenergic agents in veterinary medicine?

A

Management of cardiorespiratory function

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3
Q

Sympathomimetics

A
  • Adrenergic ants that stimulate/activate the SNS

- Agonists at a1, b1, b2 R sites; drugs that act at dopamine R sites

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4
Q

Sympatholytics

A

Reduce level of activation of the SNS

-Antagonists at a, b receptors

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5
Q

Classification of sympathomimetics

A
  1. Direct effect at adrenergic R

2. Indirect effect by causing release of NE

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6
Q

Naturally-Occurring Catecholamines

A
  1. Epi
  2. NE
  3. Dopamine
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7
Q

Structure of catecholamines

A
  • Based on benzene ring with various amine side-chains attached at the C1 position
  • If hydroxyl group present at C3 and C4 positions, agent known as catecholamine bc 3,4-dihydroxybenzene AKA catechol
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8
Q

Epinephrine

A

a1, a2, b1, b2
Non-selective, directly acting adrenergic agonist
Primarily used to support CV function during CPR

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9
Q

Storage of epinephrine

A

Light sensitive - colored glass vials, prefilled syringes inside protective packaging

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10
Q

Available formulations of epinephrine

A
  • 0.1mgmL (1:10,000)
  • 1mgmL (1:1000)
  • Also available with local anesthetic solutions for infiltration at concentrations ranging from 1:200,000 to 1:80,000
  • Most formulations contain racemic epinephrine
  • Active form = L-isomer
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11
Q

Administration of epinephrine

A

Systemically by IV injection or via airway during resuscitation (intratracheal administration)
-In humans: also available in metered aerosol preparation to treat swelling associated with upper airway obstruction due to VC effects

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12
Q

What is the active isomer of epinephrine?

A

L-isomer

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13
Q

Where are a1 R located?

A

Smooth Muscle –> BV, bronchi, GIT, urinary, uterus

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14
Q

What is the effect when a1 R are stimulated?

A

CTX of SM, VC

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15
Q

What is the MOA of the a1 R?

A

Excitatory GPCR linked to PLC –> R binding activates PLC –> increased intracellular IP3 –> increased intracellular Ca2+

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16
Q

Where are a2 R located?

A

throughout CNS this is inadequate

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17
Q

What is the effect when a2 R are stimulated?

A
  • Sedation
  • Analgesia
  • Attenuation of sympathetically-mediated responses
  • Platelet aggregation
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18
Q

What is the MOA of the a2 R?

A

Inhibitory GPCR linked to AC –> R binding reduces AC activity –> decrease intracellular [cAMP]

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19
Q

PLC

A

Phospholipase C

20
Q

IP3

A

Inositol triphosphate

21
Q

AC

A

Adenylyl cyclase

22
Q

cAMP

A

cyclic adenosine monophosphate

23
Q

PKA

A

Protein kinase A

24
Q

Where are b3 R located?

A

Adipose tissue

25
Q

What is the effect when b3 R are stimulated?

A

Lipolysis

26
Q

What is the MOA of the b3 R?

A

Excitatory GPCR linked to AC: R binding activates AC –> increased intracellular [cAMP]

27
Q

Where are b1 R located?

A

Heart

28
Q

What is the effect when b1 R are stimulated?

A

Positive inotropic, chronotropic effects

29
Q

What is the MOA of the b1 R?

A

Excitatory GPCR linked to AC: binding activates AC –> increased intracellular [cAMP]

30
Q

Where are b2 R located?

A

Smooth muscle: BV, brooch, GIT, uterus, urinary system; heart

31
Q

What is the effect when b2 R are stimulated?

A

Relaxation of smooth muscle, vasodilation

Minor positive inotropic, chronotropic effects

32
Q

What is the MOA of the b2 R?

A

Excitatory GPCR linked to AC: binding to R activates AC –> increased cAMP –> cAMP activates PKA, also increases activity of Na/K ATPase activity which causes hyper polarization

33
Q

Where are dopamine 1 R located?

A
  • Throughout CNS
  • Vascular SM, kidney
  • Sympathetic ganglia (etc - WTF is etc?)
34
Q

What is the effect when dopamine 1 R are stimulated?

A

Modulates extrapyramidal activity

Vasodilation of renal and mesenteric vasculature

35
Q

What is the MOA of the dopamine 1 R?

A

Excitatory GPCR linked to AC: receptor binding activates AC and leads to an increase in intracellular [cAMP]

36
Q

Where are dopamine 2 R located?

A
  • Throughout CNS
  • Vascular SM, kidney
  • Sympathetic ganglia (etc - WTF is etc?)
37
Q

What is the effect when dopamine 2 R are stimulated?

A

Reduced pituitary hormone output inhibit further noradrenaline release

38
Q

What is the MOA of the dopamine 2 R?

A

Excitatory GPCR linked to AC: receptor binding reduces AC activity and leads to an decrease in intracellular [cAMP]

39
Q

Epinephrine half-life

A

-Very short DT rapid metabolism –> necessitates frequent redosing or administration by infusion for a prolonged effect

40
Q

Metabolism of epinephrine

A

-Following IV admin, rapidly metabolized by mitochondrial monoamine oxidase + catechol-O-methyltransferase within liver, kidney, and circulation to inactive metabolites (3-methoxy-4-hydroxymandelic acid, metanephrine)

41
Q

Excretion of epinephrine

A

Inactive metabolites (3-methoxy-4-hydroxymandelic acid, metanephrine) conjugated with glucuronic acid or sulfates –> excreted in urine

42
Q

What are the two inactive metabolites of epinephrine?

A

3-methoxy-4-hydroxymandelic acid

Metanephrine

43
Q

Epi: renal effects

A
  • Causes release of renin from the kidney through multiple mechanisms: stimulation of intrarenal B1 /B2 R, extra renal adrenergic R
  • Renal blood flow moderately decreased DT regional VC
44
Q

Epi: anesthetic requirements

A
  • Anesthetic requirements related to the release of CNS catecholamines –> predicted that epi will increase MAC of volatile agents
  • No effect of low-dose epi on MAC of halothane reported in dogs
45
Q

Epi: respiratory effects

A
  • Small increase in minute volume through bronchodilator effects - beta 2 adrenergic R mediated
  • Pulmonary vascular resistance increased at higher dose rates reflecting agonism at pulmonary vascular alpha 1 adrenergic R
46
Q

Epi: metabolic effects

A
  • Wide-ranging effects that are dose-dependent
  • Increased basal metabolic rate –> slight increase in body temp following administration
  • Increased plasma glucose concentrations (multiple mechanisms)
  • Initial increase in serum K+ followed by hypokalemia followed by increased uptake of K+ into cells (B2 effect)
47
Q

Epi: mechanisms of increased glucose concentrations

A

-

Pharmacology (7 decks)

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