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Pharmacology > 8) Sympathomimetics > Flashcards

8) Sympathomimetics Flashcards

1
Q

Sympathomimetics

A
  • Used for cardiovascular, respiratory, and other conditions
  • Divided into subgroups based on their spectrum of action (α-, β-, or dopamine-receptor affinity) or mode of action (direct or indirect)
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2
Q

Adrenoceptors are classified as

A
  • α, β, or dopamine receptors
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3
Q

Epinephrine may be considered

A
  • Single prototype agonist

- Effects at all α- and β-receptor types

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4
Q

Separate prototypes of epinephrine

A
  • Phenylephrine (α agonist)

- Isoproterenol (β agonist)

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5
Q

Endogenous adrenoceptor agonists

A
  • Epinephrine
  • Norepinephrine
  • Dopamine
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6
Q

Catecholamines (endogenous adrenoceptor agonists)

A
  • Rapidly metabolized by COMT and MAO
  • Inactive by oral route
  • Given parenterally
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7
Q

Phenylisopropylamines

A
  • Resistant to MAO and COMT
  • Most are not catecholamines
  • Orally active (enter CNS, last much longer than catecholamines)
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8
Q

Tyramine

A
  • Rapidly metabolized by MAO (inactive orally) except in patients who are taking a MAO inhibitor drug
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9
Q

MAO inhibitors

A
  • Sometimes used in the treatment of depression

- Tyramine is found in fermented foods so patients taking MAO inhibitors may have hypertensive reactions to such foods

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10
Q

Two major enzymes are responsible for catecholamine catabolism in the brain

A
  • Catechol-O- methyltransferase (COMT)
  • Monoamine oxidase A (MAO-A)
  • Either can catalyze the first step in catecholamine catabolism
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11
Q

Alpha 1-receptor effects

A
  • Mediated by Gq

- Gq activated > a moiety activates phospholipase C > (IP3) and (DAG) released from membrane lipids

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12
Q

IP3 acts on/causes

A
  • Acts on intracellular IP3 receptors

- Causes calcium release from stores in smooth muscle cells

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13
Q

Alpha2-receptor activation results in

A
  • Inhibition of adenylyl cyclase via Gi

- Leads to the decrease of cAMP

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14
Q

β receptors (β1, β2, and β3) effects

A
  • All stimulate adenylyl cyclase via Gs

- Increase cAMP concentration in the cell

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15
Q

Dopamine D1 receptor effects (D1 and D5)

A
  • Gs activates adenylyl cyclase
  • Increase cAMP in neurons and
    vascular smooth muscle
  • Vasodilation
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16
Q

Dopamine D2 receptors effects (D2, D3, D4)

A
  • Gi reduces cAMP
  • More important in the brain

- Role as presynaptic receptors on peripheral nerves

17
Q

Alpha 1 agonists

A
  • Increase blood pressure

- Evoke compensatory reflex bradycardia (mediated by vagus)

18
Q

Alpha 2 agonists

A
  • Topical or IV = vasoconstriction

- Oral = accumulate in CNS, reduce sympathetic outflow and BP

19
Q

Beta 2 agonists and nonselective β agonists cause a significant reduction in

A
  • Arteriolar tone in the SkM vascular bed
20
Q

Beta 1 agonists

A
  • Relatively little effect on vessels

- Potent cardiac stimulants

21
Q

Dopamine

A
  • Vasodilation in renal vascular beds (via D1 receptor activation)
  • Treatment of renal failure
  • Higher doses = activates β receptors in the heart and elsewhere
  • Even higher doses = α receptor activation
22
Q

β1 and β2 receptors mediate

A
  • Increased rate of SA node/pacemaker (normal and abnormal)
  • Increased AV node conduction velocity
  • Increased cardiac force
23
Q

Baroreceptor

A
  • Mechanoreceptor

- Relays info derived from BP within the ANS

24
Q

Sympathomimetics with both α and β1 effects may cause

A
  • Reflex increase in vagal outflow (higher BP evokes baroreceptor)
  • This effect may dominate any direct beta effects on the heart rate
25
Q

A pure α agonist

A
  • Slows heart rate via the baroreceptor reflex
26
Q

A pure β agonist

A
  • Increases heart rate
27
Q

The reduction in heart rate caused by norepinephrine is the result of

A
  • Baroreceptor reflex activation of vagal nerve
28
Q

Diastolic blood pressure is affected mainly by

A
  • Peripheral vascular resistance and the heart rate
29
Q

The adrenoceptors with the greatest effects on vascular resistance are

A
  • α and β2 receptors
30
Q

The systolic pressure is the sum of

A
  • Diastolic and the pulse pressures

- thus, a function of both α and β effects

31
Q

Pulse pressure

A
  • Difference between systolic and diastolic

- Measures the heart force generated in every contraction

Pharmacology (27 decks)

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