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sympathomimetics Flashcards

1
Q

what are the sympathetic neurotransmitters?

A

adrenergic: norepinephrine and epinephrine

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2
Q

derivative of tryptophan

A

serotonin

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3
Q

monoamine

A

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

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3
Q

derivatives of tyrosine

A

dopamine, epinephrine, and norepinephrine

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4
Q

cathecholamine

A

-monoamine with catechol group (benzene with two hydroxyl groups)
-dopamine, norepinephrine, epinephrine

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5
Q

two types of metabolic enzymes

A

COMT: catechol-o-methyltranferase
MAO: monoamine oxidase

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6
Q

COMT

A

Highest activity in liver, important for metabolism of
circulating and administered catecholamines. Also at
nerve terminals.

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7
Q

MAO

A

Surface membrane protein of mitochondria
High concentrations in nerve terminals, liver, kidney, gut

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8
Q

receptor selectivity of albuterol

A

Beta2-selective

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9
Q

receptor selectivity of dobutamine

A

beta1-selectivity

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10
Q

receptor selectivity of isoproterenol

A

nonselective beta

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11
Q

receptor selectivity of clonidine

A

alpha2-selective

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12
Q

receptor selectivity of phenylephrine

A

alpha1-selective

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13
Q

receptor selectivity of norepinephrine

A

nonselective alpha

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14
Q

direct acting adrenergic receptor agonist

A

-norepinephrine (levophed)
-epinephrine (adrenalin)

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15
Q

adrenergic receptor summary alpha 1

A

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

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16
Q

adrenergic receptor summary alpha 2

A

-GI
-vasoconstriction (innervated)
-prejunctional inhibition of NE release
-in CNS: decrease CV and SNS input

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17
Q

adrenergic receptor summary beta 1

A

-Gs
-cardiac stimulation (innervated)
-secretion of renin

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18
Q

adrenergic receptor summary beta 2

A

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

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19
Q

norepinephrine (NE)

A

-activates alpha and beta receptors little afinity got beta 2
-alpha 1 agonist: vasoconstriction leading to a rise in blood pressure)
-Beta 1 agonist: cardiac stimulation by increase in force and conduction

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20
Q

epinephrine (E)

A

-activates alpha and beta receptors
-α1 agonist: Vasoconstriction leading to a rise in blood pressure
-β1 agonist: Cardiac stimulation by increasing in force, rate and conduction
-β2 agonist: Vasodilation leading to a fall in blood pressure and bronchodilation

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21
Q

dopamine (D)

A

*Lower doses
-D1 agonist (Vasodilation in renal, mesenteric and coronary arteries increasing blood flow)
-β1 agonist (Cardiac stimulation by increasing force, rate and conduction)
*High doses
-α1 agonist (Vasoconstriction leading to a rise in blood pressure)

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22
Q

direct acting adrenergic receptor agonist: norepinephrine

A

-potent alpha anf beta 1 receptor agonist
-substrate for MAO and COMT
-parenteral administration
-used as a pressor
-sodium bisulfite used in preparations to prevent oxidation

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23
Q

direct acting adrenergic receptor agonist: epinephrine

A

-potent alpha, beta 1, and beta 2 receptor agonist
-substrate for MAO and COMT
-parental administration
-sodium bisulfite used in preparation to prevent oxidation
-available as many salt: hydrochloride, nitrate, bitartrate
-uses: anaphylaxis, in combination with local anesthesics

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24
Q

actions of epinephrine

A

-Lower concentrations: effects at b 1 and b 2 predominate
-higher concentrations: effects at a 1 predominate

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25
Q

clinical use of epinephrine

A

Treatment of acute anaphylaxis or cardiac arrest; adjunct with local anesthetics

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26
Q

problems of epinephrine

A

-not orally active due to COMT and MAO breakdown in liver (first-pass metabolism)

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27
Q

epinephrine counters hypoglycemia

A

beta 2: glycogenolysis, glyconeogenesis —> increased glucose
alpha 2: inhibits insulin secretion

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28
Q

dipiveferin

A

-epinephrine dipivalate, propine
-infant glaucoma (not in US)
-lipophilic
-activated by esterase

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29
Q

actions of D1 agonist dopamine (intropin)

A

-Renal D1-receptor agonist, renal vessel dilation
-Direct and indirect b1-agonist, a1-agonist (high dose):
Sympathomimetic activity
-Cardio stimulate & systemic vasoconstrictor outside the kidney

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30
Q

clinical use of D1 agonsit dopamine

A

-shock
-acute congestive heart failure
-must be given IV

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31
Q

adrenergic receptor subtype -alpha 1 signal pathway

A

-signal via Gq pathway
-mobilize Ca++ from intracellular stores
-activate PKC
-found on: vascular smooth muscles, genitourinary smooth muscles, intestinal smooth muscles, heart, liver
-mediates vasoconstriction

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32
Q

alpha 1 receptors are clinically manipulated for

A

-agonist: nasal decongestion, vascular failure in shock and supra-ventricular tachycardia
-antagonist: hypertension, benign prostatic hyperplasia, pheochromocytoma

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33
Q

clinical use of phenylephrine

A

-nasal decongestant
-Mydriasis without cycloplegia
-Pressor
-Vasoconstrictor in regional anesthesia

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34
Q

administration of phenylephrine

A

-parenteral, oral, local
-substrate for MAO

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35
Q

direct alpha 1 agonist

A

phenylephrine

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36
Q

problems of phenylephrine

A

few: although not a very effective decongestant

37
Q

direct acting adrenergic receptor agonst: a 1 receptor agonists: 2-aralkylimidazolines

A

-partial agonist at alpha receptors
-administered locally/topically to promote vasoconstriction
-basic nature of imidazoline ring causes compounds to exist in ionized form at physiologic pH
-tachyphylaxix/ desensitization
uses: nasal and ophthalmic decongestants

38
Q

adrenergic receptor subtypes: beta 1,2,3
signal

A

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

39
Q

Beta 1 receptor found in

A

heart:
-Increases force of contraction (inotropy)
-Increases heart rate (chronotropy)
-increases conduction velocity in AV node
kidney:
-increases renin release

40
Q

clinical manipulated for beta 1 receptors

A

-agonist: shock, congestive heart failure
-antagonist: hypertension, angima, arrhythmias, congestive heart failure

41
Q

beta 2 receptors are found in

A

smooth muscles: relaxation, especially bronchial smooth muscle
vasodilation

42
Q

beta 2 receptors are clinically manipulated for

A

-agonist: asthma, premature labor
-antagonist: glaucoma

43
Q

beta 3 receptor are found in

A

-urinary bladder: relaxation, prevention of urination

44
Q

beta 3 receptors are clinically manipulated for

A

agonist: overactive bladder

45
Q

direct acting adrenergic receptor agonist: beta receptor agonist: isoproterenol

A

-non-selective beta receptor agonist
-bronchodilation
-increased cardiac output
-metabolized by conjugation reactions (phase II) and by COMT
-not sensitive to MAO
-administration: oral, parenteral, local
-uses: asthma, chronic obstructive pulmonary disease (COPD), cardiostimulant

45
Q

action of isoproterenol

A

b 1 and b 2 receptor agonist;
*Positive inotropic & chronotropic effects, thereby increasing CO
*In peripheral vessels, stimulation of β 2 -receptors results in vasodilation &
reduced peripheral resistance (may cause blood pressure to fall)

45
Q

clinical use of isoproterenol

A

*Emergency use to increase the heart rate in patients with bradycardia or heart
block before pacemaker implantation
*Patients with systolic dysfunction & slow heart rates with high systemic vascular
resistance: after cardiac surgery in patients who previously used β-blockers
*Asthma and COPD

45
Q

selective beta 2 receptor agonist: resorcinol derivatives

A

-selective beta 2 receptor agonist
-bronchodilation
-cardiac effects observed only at high doses
-not metabolized by MAO and COMT
-longer duration of actionn than isoproternol
-administration: oral, parenteral, local
-uses: asthma, COPD, terbutaline used as tocolytic(prevent premature labor)

45
Q

selective Beta 2 receptor agonist: meta hydroxymethyl derivatives

A

-selective beta 2 receptor agonist
-bronchodilation
-cardiac effects observed only at high doses
-not metabolized by MAO and COMT
-longer duration of action than isoproterenol
-administration: oral, local
-uses: asthma, COPD

45
Q

mirabegron

A

direct acting beta 3 receptor agonist

45
Q

long acting beta 2 receptor agonsit

A

-Selective b2 receptor agonists
-Bronchodilation
-Not metabolized by MAO or COMT
-Onset of action:
Salmeterol 10-20 min
Formoterol < 5 min
-Longer duration of action
-Administration: inhaled (metered-
dose inhaler and powder)
-Uses: Long-term Asthma, COPD
-Not recommended for acute
treatment of asthma symptoms

45
Q

action of albuterol and terbutaline

A

beta 2 agonist

46
Q

clinical use of mirabegron

A

overactive bladder

46
Q

mixed beta 1 and alpha 1 receptor agonist

A

-Dopamine derivative
-Available as a racemic mixture
-(+)-enantiomer: potent b1 receptor agonist
-(-)-enantiomer: potent a1 receptor
agonist, potency for b receptors reduced 10X
-racemic exerts a much stronger inotropic than chronotropic effect
-Metabolized by COMT and conjugation, not sensitive to MAO
-Short half-life (~2 min)
-Administered: i.v. infusion (why?)
-Use: Acute heart failure, shock, Labaoratory “stress test”

46
Q

clinical use of albuterol and terbutaline

A

-Asthma: albuterol and terbutaline
-Tocolytic: terbutaline (to relax uterus during premature labor)

46
Q

problems of albuterol and terbutaline

A

minor cardiac stimulation

46
Q

problems of mirabegron

A

-slow onset (8 weeks)
-hypertension

47
Q

alpha 2 receptor clonidine

A

-imidazolidine
-selective alpha 2 receptor agonist
-basicity of the guanidine group (pKa 13.6) is decreased to Pka 8 because of the attachment to the dichlorophenyl ring
-activation of alpha 2 receptors in CNS decreases SNS activity and presynapes

48
Q

action of clonidine

A

-a 2 receptor agonist; in the CNS (brainstem) to decrease sympathetic nervous
system activity to the heart and blood vessels
- presynaptic a 2 receptor, decrease cAMP, inhibit certain calcium channels
(decrease vesicular release), activate certain potassium channels
(hyperpolarize)

48
Q

clinical use of clonidine

A

-hypertension
-neuropathic pain/ opiate withdraw
-ADHD

49
Q

administration of clonidine

A

oral, parenteral, transdermal

50
Q

problems with clonidine

A

hypotension, sedation, dry mouth – withdrawal syndrome sometimes seen after prolonged use (hypertension, tachycardia, angina or myocardial infarction)

50
Q

methyldopa analpha 2 receptor agonist

A

-A prodrug metabolized to active a2 receptor agonist, (1R, 2S)-a- methylnorepinephrine
-Act at CNS a2 receptors to decrease sympathetic outflow
-Water soluble, ester hydrochloride salt Methyldopate is used for parenteral solutions
-Administration: Methyldopa, oral; Methyldopate; parenteral
-Uses: Hypertension (especially during pregnancy)

51
Q

alpha 2 adrenergic agonist reduce blood pressure by reducing sympathetic output from the brain

A

-inhibition of NE release
-decreased sympathetic tone in CNS
-decr HR
-decr contractility
-decr renin release
-decr vasoconstriction

52
Q

alpha 2 receptor agonist guanabenbz and guanfacine

A

-“Open-ring” imidazolidines
-Two atom bridge to the guanidine group decreases the pKa so that the drug is mostly non-ionized at physiological pH
-Guanabenz has the shortest t-1/2 at ~ 6 hours. Half-life of clonidine and guanfacine is 12-16 hours
-Administration: oral
-Uses: Hypertension, ADHD (guanfacine)

52
Q

action of brimonidine

A

-a2 receptor agonist
-Inhibits aqueous humor production (acute effect) and stimulate
aqueous humor outflow (chronic effect)

53
Q

clinical use of brimonidine

A

glaucoma

54
Q

problems ofbrimonidine

A

allergic conjunctivitis

55
Q

indirect acting sympathomimetics

A

-amphetamine, pseudoephrine ephedrine, tyramine
-promotes release of NE via reverse action of plasma membrane transporter
-clinical uses: amphetamines, ADHD, narcolepay, anorexiant, nasal decongestants

56
Q

what is one of the most potent stimulators

A

amphetamine

57
Q

clinical use of amphetamine and methamphetamine

A

-Narcolepsy
-ADHD (first-line: low doses increase wakefulness, alertness, ability to concentrate)
-also used as appetite suppressants but not approved for this use

58
Q

problems of Indirect Sympathomimetics:
Ephedrine and Pseudoephedrine

A

Increased blood pressure, increased heart rate via enhanced NE signaling
from SNS

58
Q

ephedrine and pseudoephedrine are ____- active

A

orally

58
Q

problems of amphetamine and methamphetamine

A

-At therapeutic doses: anorexia, poor growth, sleep disturbances, jitteriness
-At toxic dose
-Increased blood pressure, increased heart rate via enhanced NE signaling:
Potential for stroke, cardiac arrhythmias, myocardial infarction, and sudden death
-From CNS: agitation, confusion, addiction (Schedule II drug). Amphetamine group
of drugs release dopamine which lead to CNS effects

58
Q

ADHA

A

characterized by excessive
motor activity, difficulty in sustaining attention, and impulsiveness. (low DA)

58
Q

Indirect-acting sympathomimetics:
D-(-)-Ephedrine vs. L-(+)-Pseudoephedrine

A

-Alkaloid obtained from the stemsof Ephedra. Also found in mahuang.
-D-(-)-Ephedrine has desired ( R) configuration at b-OH and (S)- configuration at the a carbon, so has direct alpha and beta agonist activity at adrenergic receptors
-L-(+)-Pseudoephedrine is the (S,S)-diastereoisomer; (S)- configuration of b-OH reduces agonist activity-major mechanism is via reversal of the transporter

58
Q

clinical use of Indirect Sympathomimetics:
Ephedrine and Pseudoephedrine

A

-Pseudoephedrine (Sudafed): nasal decongestion
-Ephedrine (Ephedra): has direct alpha and beta effects. has been used as a “natural product” for weight loss and to increase muscle strength– has led to increased blood pressure, strokes, deaths. Banned in dietary supplements in US in 2004

59
Q

norepinephrine transporter inhibitors

A

cocaine, methyphenidate, atomoxetine

59
Q

action of cocaine

A

-Block NET, DAT
-Decrease uptake
-Enhance NE signaling by keep more transmitter in synaptic cleft

59
Q

important take away from indirect acting sympathomimetics

A

co-administration with other indirect acting drugs can lead to a hypertensive crisis

59
Q

wine/cheese effect

A

-tyramine high levels in beer, cheese, wine, and many processed meat or sausage
-Tyramine is an indirect sympathomimetic
agent and can produce strong effects if it
reaches sympathetic nerve terminals.
-Normally, almost all ingested tyramine is
rapidly broken down by MAO in the liver.
-MAO inhibitors decrease the breakdown of
tyramine resulting in a bolus release of NE
potentially resulting in a hypertensive crisis

59
Q

clinical use of cocaine

A

Local anesthetic (sodium channel blocker) for nasal mucosa and vasoconstriction

60
Q

side effects of cocaine

A

Peripheral
-Increased blood pressure and heart rate
-Potential for stroke, cardiac arrhythmias, myocardial infarction and sudden death
(Len Bias 1986, 2 nd overall pick)
Central: Euphoria, Increase alertness, Arousal, Addictive

61
Q

action of methylphenidate

A
  • Blocks NE and DA reuptake transporters that transport monoamines from synaptic cleft
    back to presynaptic terminal
    -Overall effect: enhance NE and DA signaling
62
Q

clinical use of methylphenidate

A

ADHD, narcolepsy (similar to amphetamine)
Recommended for preschool children with ADHD

63
Q

problems with methylphenidate

A
  • (similar to amphetamine)
  • Priapism (prolonged penile erection): rare but serious
  • Also addictive potential (C-II drug) via enhanced DA signaling
63
Q

clinical use of atomoxetine

A

attention deficit hyperactivity disorder (ADHD)
-note: not a controlled substance and stimulants so isnt associates with agitation or sleeplessness

64
Q

action of atomoxetine

A

selective inhibitor of NET and thus enhances NE levels

65
Q

problems of atomoxetine

A

-Black-box warning for suicidal ideation
-Priapism (prolonged penile erection): rare but serious
-May take longer than stimulants for effect
-May be less effective than stimulants

65
Q

other non stimulants for ADHD

A

Guanfacine (Intuniv): alpha2 agonist
Clonidine (Kapvay): alpha2 agonist

66
Q

stimulants for ADHD

A

Amphetamine/methamphetamine
Methylphenidate

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