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PHRM 825 Exam 1 > Sympathomimetics > Flashcards

Sympathomimetics Flashcards

1
Q

sympathetic neurotransmitters: adrenergic

A

norepinephrine (noradrenaline)
epinephrine (adrenaline)
-the only difference between these is that epinephrine has a methyl group off of the N

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2
Q

derivatives of tryptophan

A

serotonin

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3
Q

derivatives of tyrosine

A

norepinephrine, epinephrine, dopamine

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4
Q

monoamines

A

contain one amino group connected to aromatic ring by two-carbon chain
-serotonin, dopamine, norepinephrine, epinephrine, (histamine)

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5
Q

catecholamines

A

monoamine with catechol group (benzyne with two hydroxyl groups), derivatives of tyrosine
-dopamine, norepinephrine, epinephrine

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6
Q

norepinephrine neurotransmission

A
  1. tyr transported into noradrenergic ending/varicosity by Na+ dependent carrier
  2. tyr converted to dopa by tyrosine hydroxylase, converted to dopamine by dopa decarboxylase
  3. dopamine transported to vesicle by vesicular monoamine transporter (VMAT)
    -same carrier transports NE
  4. dopamine converted to NE in vesicle by dopamine-b-hydroxylase
  5. release of transmitter occurs when action potential opens voltage-sensitive Ca2+ channels and increases intracellular Ca2+, fusion of vesicles with surface membrane causes expulsion of NE
  6. NE binds to adrenergic receptors on postsynaptic cell
  7. NE binds to regulatory receptors present on presynaptic terminal
  8. NE diffuses out of cleft/reuptaken into cytoplasm of terminal by NET where it’s metabolized by MAO and transported by VMAT into vesicles
  9. NE can diffuse away from synaptic cleft to other cells, degraded by COMT
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7
Q

where does dopamine become norepinephrine?

A

presynaptic vesicle

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8
Q

where does norepinephrine become epinephrine?

A

adrenal medulla

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9
Q

metabolic enzymes: COMT

A

catechol-O-methyltransferase
-highest activity in liver, important for metabolism of circulating and administer catecholamines
-at nerve terminals

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10
Q

metabolic enzymes: MAO

A

monoamine oxidase
-surface membrane protein of mitochondria
-high concentrations in nerve terminals, liver, kidney, gut

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11
Q

primary ANS receptors

A

adrenoceptors
-alpha: a1, a2
-beta: b1, b2, b3

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12
Q

direct acting adrenergic receptor agonists

A

levophed: norepinephrine
adrenalin: epinephrine

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13
Q

stereochemistry for catecholamines

A

have a specific spatial orientation for binding to a receptor

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14
Q

adrenergic receptors: a1 (Gq)

A

vasoconstriction (innervated)
pupillary dilation
ejaculation
inhibition of micturition
GI inhibition

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15
Q

adrenergic receptors: a2 (Gi)

A

vasoconstriction (uninnervated)
prejunctional inhibition of NE release
in CNS: decrease CV SNS input

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16
Q

adrenergic receptors: b1 (Gs)

A

cardiac stimulation (innervated)
secretion of renin

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17
Q

adrenergic receptors: b2 (Gs)

A

cardiac stimulation (uninnervated, minor)
bronchodilation
uterine relaxation
GI inhibition
vasodilation (uninnervated)

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18
Q

binding preference for epinephrine

A

b1, b2 > a1, a2

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19
Q

binding preference for norepinephrine

A

a1, a2, b1

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20
Q

NE receptors and CV effects

A

activates a and b1 receptors, little affinity for b2
-a1 agonist: vasoconstriction leading to rise in BP
-b1 agonist: cardiac stimulation by increase in force and conduction

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21
Q

E receptors and CV effects

A

activates a and b receptors
-a1 agonist: vasoconstriction leading to rise in BP
-b1 agonist: cardiac stimulation by increasing force, rate, and conduction
-b2 agonist: vasodilation leading to lower BP and bronchodilation
–target for allergy attacks to open airways

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22
Q

D receptors and CV effects

A

lower doses
-d1 agonist: vasodilation in renal, mesenteric, and coronary arteries, increase blood flow
-b1 agonist: cardiac stimulation by increasing force, rate, and conduction
high doses
-a1 agonist: vasoconstriction leading to rise in BP

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23
Q

direct acting adrenergic receptor agonists: NE

A

potent a and b1 receptor agonist
substrate for MAO and COMT: both metabolize NE quickly
parenteral administration
used as a pressor
sodium bisulfite used in preparations to prevent oxidation

24
Q

direct acting adrenergic receptor agonists: E

A

potent a, b1, and b2 receptor agonist
substrate for MAO and COMT
parenteral administration
sodium bisulfite used in preparations to prevent oxidation
available as many salts: hydrochloride, nitrate, bitartrate
uses: anaphylaxis, in combination with local anesthetics

25
Q

epinephrine

A

action:
-low concen.: effects at b1 and b2 predominate
-high concen.: effects at a1 predominate
clinical use: Tx of acute anaphylaxis and cardiac arrest, adjunct with local anesthetics
problems: not orally active due to COMT and MAO breakdown in liver (first pass metabolism), can produce unwanted effects through broad activation of adrenergic receptors

26
Q

epinephrine and hypoglycemia

A

increase blood glucose levels
-b2: glycogenolysis, gluconeogenesis
-a2: inhibits insulin secretion

27
Q

D1 agonist dopamine

A

action:
-renal D1-receptor agonist, renal vessel dilation
-direct and indirect b1-agonist, a1-agonist (high dose): sympathomimetic activity
-cardio stimulate and systemic vasoconstrictor outside the kidney
clinical use: shock, acute congestive heart failure
-MUST BE GIVEN IV: can’t withstand metabolism
selective D1 agonist fenoldopam: severe hypertension in hospitalized patients

28
Q

adrenergic receptor subtypes: a1

A

signal via Gq pathway
-metabolize Ca2+ from intracellular stores, activate PKC
-found on vascular smooth muscle, genitourinary smooth muscle, intestinal smooth muscle, heart, liver
mediates vasoconstriction
clinically manipulated for…
-agonist: nasal decongestion, vascular failure in shock and supraventricular tachycardia
-antagonist: hypertension, benign prostatic hyperplasia, pheochromocytoma
drugs: phenylephrine, oxymetazoline

29
Q

direct a1 agonist: phenylephrine

A

clinical use: nasal decongestant, mydriasis without cycloplegia, pressor, vasoconstrictor in regional anesthesia
admin: parenteral, oral, local
substrate for MAO
problems: few (not very effective decongestant)
differences from epi
-missing OH group

30
Q

SAR: NE

A

R1: H
R2: H
receptor selectivity: a
MAO: more affinity

31
Q

SAR: E

A

R1: -CH3
R2: H
receptor selectivity: a, b1
MAO: slightly less affinity

32
Q

SAR: isoproterenol

A

R1: -CH(CH3)2
R2: H
receptor selectivity: b1, b2
MAO: less affinity

33
Q

SAR: n-tert-butylnorepinephrine

A

R1: -C(CH3)3
R2: H
receptor selectivity: b2
MAO: minimal

34
Q

catechol ring modifications for selectivity: catechol

A

isoproterenol
b selectivity

35
Q

catechol ring modifications for selectivity: resorcinol

A

metaproterenol
b2 selectivity (no COMT)

36
Q

catechol ring modifications for selectivity: meta-hydroxymethyl

A

albuterol
b2 selectivity (no COMT)

37
Q

catechol ring modifications for selectivity: only meta-OH

A

phenylephrine
a1 selectivity

38
Q

direct acting adrenergic receptor agonists: a1 receptor agonists, 2-aralkylimidazolines

A

partial agonists at a receptors
administered locally/topically to promote vasoconstriction
basic nature of imidazoline ring causes compounds to exist in ionized form at physiologic pH
-cation is resonance stabilized allowing the + charge to be spread over the entire 3 atom system: imidazolines are more basic
tachyphylaxis/desensitization
uses: nasal and ophthalmic decongestants
drugs: naphazoline, tetrahydrozoline, oxymetazoline

39
Q

adrenergic receptor subtypes: b1, b2, b3

A

signal through Gs
-activate adenylyl cyclase
-increase cAMP
-increase cAMP-dependent protein kinase activity
-results in phosphorylation of ion channels and other proteins

40
Q

b1 receptors

A

found in…
-heart: increase force of contraction, HR, conduction velocity in AV node
-kidney: increase renin release
clinically manipulated for…
-agonist: shock, congestive heart failure
-antagonist: hypertension, angina, arrhythmias, congestive heart failure

41
Q

b2 receptors

A

found in…
-smooth muscle: relaxation, especially bronchial
-vasodilation
clinically manipulated for…
-agonist: asthma, premature labor
-antagonist: glaucoma

42
Q

b3 receptors

A

found in…
-urinary bladder: relaxation, prevention of urination
clinically manipulated for…
-agonist: overactive bladder

43
Q

direct acting b adrenergic receptor agonists

A

non-selective: isoproterenol
mixed b1, a1: dobutamine
b2 selective: terbutaline, metaproterenol, albuterol, salmeterol, ritodrine
b3 selective: mirabegron

44
Q

direct acting non selective b receptor agonists: isoproterenol

A

catechol: nonselective
bronchodilation
increased cardiac output
metabolized by conjugation reactions (phase II) and COMT
not sensitive to MAO
admin: oral, parenteral, local (inhaled)
uses: asthma, COPD, cardiostimulant

45
Q

isoproterenol

A

action:
-b1 and b2 receptor agonist
-positive inotropic and chronotropic effects, thereby increasing CO
-peripheral vessels: stimulation of b2 receptors results in vasodilation and reduced peripheral resistance (can cause BP to fall)
clinical use
-emergency to increase HR in patients with bradycardia or heart block before pacemaker implantation
-systolic dysfunction and slow HR with high systemic vascular resistance (after cardiac surgery in patients with previous use of b-blockers)
-asthma and COPD
note: not routinely used, E and D more common

46
Q

selectivity of adrenergic receptor agonists

A

phenylephrine has more selectivity for a1, low for all b
epinephrine has next selectivity for a1, second for b1 and b2
NE has third selectivity for a1, third for b1 and b2 (100 fold difference with E)
isoproterenol has least selectivity for a1, most for b1 and b2

47
Q

direct acting selective b2 receptor agonists: metaproterenol, terbutaline

A

resorcinol derivatives
bronchodilation, cardiac effects only at high doses
not metabolized by MAO or COMT
longer duration of action than isoproterenol
admin: oral, parenteral, local (inhaled)
uses: asthma, COPD
-terbutaline used as tocolytic (prevent premature labor)

48
Q

direct acting selective b2 receptor agonists: albuterol, salmeterol

A

meta hydroxymethyl derivatives
bronchodilation, cardiac effects only at high doses
not metabolized by MAO or COMT
longer duration of action than isoproterenol
admin: oral, local (inhaled)
uses: asthma, COPD

49
Q

direct long acting selective b2 receptor agonists: salmeterol, formoterol

A

bronchodilation
not metabolized by MAO or COMT
onset of action
-salmeterol: 10-20 min
-formoterol: <5 min
longer duration of action
admin: inhaled (metered dose inhaler and powder)
uses: long-term asthma, COPD
not recommended for acute Tx of asthma symptoms

50
Q

b2 agonist: albuterol and terbutaline

A

action: b2 receptor agonist
clinical use
-asthma: albuterol and terbutaline
-tocolytic: terbutaline (relax uterus during premature labor)
problems: minor cardiac stimulation

51
Q

direct acting mixed b1, a1 receptor agonists: dobutamine

A

dopamine derivative, available as racemic mix
-+ enantiomer: potent b1 receptor agonist
– enantiomer: potent a1 receptor agonist, potency for b receptors reduced 10x
-exerts much stronger inotropic than chronotropic effect
metabolized by COMT and conjugation, not sensitive to MAO
short half life (~2 min)
admin: IV
uses: acute heart failure, shock, laboratory “stress test”

52
Q

direct acting b3 receptor agonists: mirabegron

A

approved July 2012
clinical use: overactive bladder
problems: slow onset (8 weeks), hypertension

53
Q

adrenergic receptor subtypes: a2

A

signals through Gi
-inhibit adenylyl cyclase
-activate certain K+ channels
-inhibit neuronal Ca2+ channels
found pre-synaptically and function as autoreceptors to inhibit sympathetic output
-results in decreased transmitter release
clinically manipulated for…
-agonist: hypertension, pain, glaucoma

54
Q

direct acting a2 adrenergic receptor agonists

A

clonidine
methyldopa
guanabenz
guanfacine
brimonidine
apraclonidine
tizanidine

55
Q

direct acting a2 adrenergic receptor agonists: clonidine

A

(phenylimino)imidazolidine
basicity of guanidine group (pKa = 13.6) is decreased (pKa = 8) because of attachment to dichlorophenyl ring
activation of a2 receptors in CNS (decrease SNS activity) and presynapses

56
Q
A

PHRM 825 Exam 1 (4 decks)

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