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Pharm > Sympathomimetics > Flashcards

Sympathomimetics Flashcards

1
Q

Sympathomimetic

A

mimics activation of the sympathetic nervous system.

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2
Q

Direct vs indirect acting sympathomimetics

A

Direct-acting sympathomimetics
- Receptor agonists at alpha or beta adrenergic receptors

Indirect-acting sympathomimetics

  • Agents that cause the release of NE
  • Agents that block the reuptake of NE
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3
Q

Stuff in the eye

A

alpha one receptor causes constriction of the radial muscle causing dilation (mydriasis)

Parasympathetic causes contraction of the circular muscle (miosis) and contraction of the ciliary mucsle (accommodation)

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4
Q

adrenoreceptor on bronchial smooth muscle

A

beta 2 –> relaxation

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5
Q

adrenoreceptors on GI tract

A

alpha 2, beta 2

Think number 2s when you gotta go number 2.
remember that you’re holding it– this is sympathetic, after all

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6
Q

adrenoreceptors on the urinary bladder

A

detrusor muscle- beta

trigone/ sphincter- alpha 2

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7
Q

adrenoreceptors on the uterus

A

alpha 1, beta 2

causes contraction-relaxation

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8
Q

adrenergic receptors for glycogenolysis

A

skeletal muscle- beta
liver- alpha 1 and beta 1

Think “L-1-ver”

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9
Q

adrenergic receptors for lipolysis

A

beta 2 and 3 (increase)

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10
Q

adrenergic receptors for renin secretion

A

beta 1, increases

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11
Q

adrenergic receptor for insulin secretion

A

alpha 2, beta 2

The 2s. There are 2 “i”s in “insulin”

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12
Q

Rules of thumb for smooth muscle

A

Alpha1 (a1) Receptors
Stimulate contraction of all smooth muscle
Vascular smooth muscle Vasoconstriction
Glandular smooth muscle

Beta2 (b2) Receptors
Relax smooth muscle (e.g., lungs; arterioles)

Muscarinic Cholinergic Receptors
Contract smooth muscle
Apparent discrepancy – ACh & muscarinic agonists given IV cause vasodilation, due to release of nitric oxide (NO)
Different intracellular signal than a1 receptors

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13
Q

Modes of action for direct, indirect, and mixed-acting agents

A

Direct Receptor Agonists
directly stimulate receptor
epinephrine, NE, etc.

Indirect Acting Agents
release NE or block reuptake
amphetamines, tyramine

Mixed Acting Agents
both NE release and receptor activation

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14
Q

alpha 1 adrenergic effects

A

vasoconstriction
contraction of vascular smooth muscle

a1 vasoconstriction
a1mydriasis (dilates pupil)
 contraction of iris radial muscle
a1 contraction of spleen
a1 contraction of uterus
a1 contraction of pilomotor muscle (erects hair)
a1 increases force of contraction in heart
less important than b1 effect

Metabolic
a1 stimulates glycogenolysis

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15
Q

a2 Adrenergic Effects

A

CNS
- Postsynaptic receptors –multiple effects

Platelets
- Stimulate platelet aggregation

Nerve terminals

  • Adrenergic and cholinergic nerve terminals
  • Auto-receptors inhibit neurotransmitter release

Some vascular smooth muscle - contraction

Metabolic

  • inhibit insulin release
  • Fat cells – inhibit lipolysis
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16
Q

Beta 1 adrenergic effects

A 
b1 Heart
stimulation of heart rate
- chronotropic effect
stimulation of force of contraction
- inotropic effect

stimulate renin release

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17
Q

Beta 2 adrenergic effects

A

Smooth Muscle Relaxation b2
relaxation of bronchioles b2
relaxation of uterus b2
relaxation of vascular smooth muscle b2 (vasodilation, certain vascular beds only)
relaxation of detrusor (bladder) b2
relaxation of intestinal smooth muscle b2

Skeletal Muscle
b2 – stimulates potassium uptake

glycogenolysis in the liver

stimulates insulin release

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18
Q

Beta adrenergic effects: metabolic and hormonal

A

glycogenolysis b2 (liver)
lipolysis b3 (fat cells)
stimulation of insulin release b2
stimulation of renin release b1

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19
Q

Dopamine Effects

A

CNS
D1, D2, D3, D4, D5
Essential neurotransmitter in many different neural circuits

*** Renal Afferent Blood Vessels
D1 – Dilation
Increase blood flow to kidney

Nerve Endings
D2 – Modulate neurotransmitter release

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20
Q

mechanism of action for beta and alpha 2 receptors

A

GDP exchanged to GTP, adenylyl cyclase increases cAMP –> protein kinase, enzymes

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21
Q

alpha-1 receptor signaling

A

Gq

Phospholipase C–> IP3 –> calcium freed

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22
Q

Rank Order of Potency at Receptors

A 
a1- Epi > NE » Iso
Phenylephrine
a2- Epi > NE » Iso
Clonidine
b1- Iso > Epi = NE
Dobutamine
b2- Iso > Epi >>NE
Albuterol
b3- Iso = NE > Epi
No selective agonist clinically available
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23
Q

Baroreceptor Reflex Control of Heart Rate and Blood Pressure

A

Beta 1- stimulation of heart rate and force

muscarinic- decrease in heart rate

alpha 1- vasoconstriction

beta 2- vasodilation

24
Q

Epinephrine and the heart

A

positive chronotropic effect
positive inotropic effect
increased conduction in atria, A-V nodes & purkinje fibers
increased oxygen consumption
the work of the heart is increased substantially

25
Q

Epi - Blood Vessels

A

Epinephrine stimulates both
a1 vasoconstriction
b2 vasodilation

Epinephrine is more potent at b2 than a1
NE = Epi at b1; Epi>NE at a1, Epi&raquo_space;NE at b2 ***
At high doses, a1 vasoconstriction predominates

26
Q

Distribution and density of a & b receptors differs in different vascular beds

A

skeletal muscle both b2 and a1 present
dose-dependent vasodilation (b2) or vasoconstriction (a1)
coronaries vasodilation due to both b2 and metabolic
(NO, adenosine)
kidney, skin, mucosa, primarily a1 vasoconstriction
mesenteric beds, both b2 and a1, density varies
cerebral unchanged
pulmonary vasoconstriction a1

27
Q

Epi - Smooth Muscle

A 
Bronchial relaxation b2
GI-relaxation; slight decrease in muscle tone
Bladder 
relax detrusor b2
contract sphincter a1
Spleen contraction
Eye - mydriasis, lowers IOP
Uterus - relax (b2)during last month of pregnancy
28
Q

Epi - Glands

A

Lacrimation (a1 secretion)
Sweating (palms) and piloerection (a1)
Salivation - scant, mucous secretion
Pancreas - blocks insulin release (a2 inhibit > b2 stimulate)

29
Q

Epi - Metabolic Effects

A

Calorigenic effect
Glycogenolysis and gluconeogenesis by liver (a1, b2)
Lipolysis - increased free fatty acids (a1, b1, b2, b3) (a2 inhibit)

30
Q

Epi - Clinical Uses

A

Anaphylaxis (drug of choice)

  • bronchodilation b2
  • vasoconstriction a1
  • maintains BP, prevents spread of antigen
  • inhibits release of histamine and other allergic mediators from mast cells (b2)
  • reduced edema
31
Q

Epi - Other Uses

A 
Asthma (pediatrics)
Racemic Epi delivered by nebulizer is used for bronchodilation
Glaucoma – rarely used
*** Infiltration with local anesthetics for vasoconstriction to keep anesthetic local
Cardiac resuscitation 
Topical hemostatic
arterioles and capillaries
ineffective for large blood vessels
32
Q

Epi - Adverse Effects

A

Arrythmias
especially with certain gaseous anesthetic agents
Cerebral hemorrhage from elevated blood pressure when given high dose i.v.
Tissue necrosis from vasoconstriction at site of injection
CNS - fear, anxiety, headache

33
Q

Epi- Contraindications

A

Hypertension
Shock (hypovolemic) - further compromised blood flow
Hyperthyroidism
Angina pectoris - increases O2 demand
Asthmatics with degenerative heart disease

34
Q

Norepinephrine (Levophed)

A

Natural sympathetic and CNS neurotransmitter
Agonist at alpha 1, alpha 2, beta 1 receptors

** very weak (low potency) at beta 2 receptors

Heart:
direct: positive inotropic and chronotropic (1)
indirect: reflex bradycardia (blocked by atropine)
net effect: increase force; decreased rate
slow, forceful heartbeat
Blood vessels: alpha1-mediated vasoconstriction; BP

35
Q

Norepinephrine administration and side effects

A

Administration: IV infusion to maintain blood pressure during spinal anesthesia or hypotensive shock.

Side Effects: anxiety, slow forceful heart beat; headache

36
Q

Isoproternol (Isuprel)

A

Synthetic catecholamine
** Potent agonist at all beta receptors; no alpha effects
Heart beta 1 increased heart rate and force
Blood vessels:
beta 2 vasodilation in skeletal muscle & mesentery
decreased diastolic BP
increased systolic BP
no change or decreased mean BP

37
Q

Other isoproternol effects

A

Smooth muscle: relaxes bronchial and uterine
Metabolic: increases free fatty acids
stimulates insulin release & glycogenolysis
Clinical Uses: can be used (not 1st choice) in cardiac arrest, MI, cardiogenic shock to increase cardiac output
Side Effects: tachycardia, headache, flushing, arrhythmias, anginal pain

38
Q

Dopamine (Intropin)

A

Important neurotransmitter in CNS
CNS receptors: D1, D2, D3, D4, D5
Peripheral receptors: D1, beta 1, alpha
Pharmacological effects

blood vessels: *** vasodilates renal and mesenteric (D1 receptors) increase blood flow to kidney
heart: mild increase in rate and force (partial agonist beta 1)
blood vessels: high doses cause vasoconstriction & increased BP (alpha 1)

39
Q

Dopamine Clinical uses

A

Cardiogenic Shock
Increases cardiac output and enhances perfusion of kidney
Must monitor BP carefully because higher infusion rate or dose causes vasoconstriction and decreased tissue perfusion
Sometimes used in chronic CHF

40
Q

Dobutamine (Dobutrex)

A

Beta 1-selective agonist
actually complicated beta 1 agonist, alpha 1 agonist/antagonist
Clinically mostly 1-effects
positive inotropic & some increase in rate
Cardia output increases
little vascular effect
Clinical Use: MI, CHF, cardiogenic shock
Adverse effects: may increase size of infarct
potential arrhythmias

41
Q

alpha 1 -Adrenergic Agonists and mixed-acting alpha agonists

A

= Pressor Agents

Phenylephrine (Neosynephrine) Prototype
Methoxamine (Vasoxyl)
Midodrine (Pro Amatine)

Mixed Acting Alpha agonists
Mephentermine (Wyamine sulfate)
Metaraminol (Aramine)

42
Q

Phenylephrine

A

prototype alpha-1 agonist

Effects:
vasoconstriction
increase peripheral resistance; increase BP
increased blood pressure causes reflex bradycardia (blocked by atropine)

43
Q

Phenylephrine uses

A

Uses: to maintain BP in hypotensive states
– spinal anesthesia

paroxysmal atrial tachycardia
– induces baroreceptor reflex slowing of rate

Nasal decongestant

Glaucoma: decreases IOP
– deceases aqueous humor production

Infiltration with local anesthetic (usually epi)

44
Q

beta-2 selective agonists

A

About 10 -fold more potent for beta 2 over beta 1
primarily greater selectivity for lung over heart

Synthetic agents that are more resistance to metabolism than catecholamines

  • longer acting
  • some orally effective
45
Q

Albuterol (Proventil, Ventolin)

A

relatively selective beta 2 (10x)

** bronchodilation **

used for treated bronchospams in asthma

  • aerosol delivery - restricts to lungs, decreases systemic absorption and side effects
  • p.o. - sometimes used, more side effects when oral

Side effects:
muscle tremors, tachycardia (1 and reflex), anxiety, restlessness, headache, hypoglycemia, hypokalemia

46
Q

Other beta2 selective agonists

A

Metaproterenol (Metaprel, Alupent)

Terbutaline (Brethine)
inhaled, PO or SC - asthma; delay delivery

Isoetharine (generic)

Ritodrine (Yutopar)
i.v.; relax uterine muscle; delay premature delivery

*** Salmeterol (Serevent)
long-acting bronchodilator for nighttime asthma

*** Formoterol (Foradil) – like salmeterol

Bitolterol (Tornalate) - prodrug; asthma

47
Q

Indirectly Acting Sympathomimetics

A

Release of NE from nerve terminals results in sympathomimetic effects
- primarily a1 and b1 receptor

Some drugs can both release NE and also directly activate receptors and thus are called mixed-acting sympathomimetics

– notably ephedrine also stimulates b2

48
Q

Tyramine

A

Tyramine is found in high levels in certain foods: beer, red wine, cheese.
Normally rapidly degraded by MAO in GI tract and liver
Patients taking MAO inhibitor (for depression) get high level of tyramine
Tyramine displaces NE from nerve terminal - causes hypertensive crisis, MI, stroke.

49
Q

Cocaine

A

Cocaine, tricyclic antidepressants (TCAs), and SNRIs competitively block NE reuptake into nerve terminal

NE levels in synapse higher for longer periods

50
Q

Amphetamines

A

Mechanism:
cause release of NE from adrenergic nerve endings and inhibit net NE reuptake by competing with NE binding to uptake transporter
result more NE in synapse and at receptor sites for a longer period; i.e., sympathomimetic

*** Relatively hydrophobic and readily enter CNS

Effective orally
Less metabolized than catecholamines
Effects last for several hours
Effects from both peripheral and CNS
Many different amphetamines:
d and l isomers, dextroamphetamine, methamphetamine [Tradename=Adderal]

related drugs: methylphenidate (Ritalin),

(fenfluramine, phenylpropanolamine, phenmetrazine, diethylpropion, mazindol)

51
Q

Amphetamines in the CNS

A

increase NE, DA and 5-HT
increase alertness, decrease fatigue, increase mood
increase amount of work but also number of errors
physical performance improved acutely
rebound fatigue and depression
potential for dependence, schedule II controlled substances

52
Q

Amphetamines - cardiovascular effects

A

vasoconstriction, increased heart rate

effects vary with dose and drug

53
Q

clinical uses of amphetamines

A

Narcolepsy
ADHD
Obesity
- depress appetite not metabolism; tolerance develops, usefulness is questionable

54
Q

amphetamine toxicity

A

acute overdose: signs and symptoms are extensions of therapeutic effects
CNS: restlessness, dizziness, tremor, talkative
Paranoid delusions, panic, psychosis
Cardiovascular: palpitations, headache, arrhythmias, anginal pain, circulatory collapse,
Death, convulsions, coma, cerebral hemorrhage
acidify urine, enhance urinary excretion, give sedative, sodium nitroprusside or alpha-blocker

55
Q

Ephedrine

A

Mixed acting agonist (direct and indirect)
direct: Beta-receptor agonist
indirect: releases NE
Not substrate for COMT or MAO
orally active and long-acting
CNS - stimulant
CV - mild increase force and rate, weak vasoconstriction
Lungs - mild bronchodilation
Uses: pressor agent, bronchospasm, nasal decongestant

56
Q

Nasal Decongestants

A

Local vasoconstrictors ( agonists)

Vasoconstriction in nasal mucosal edema (runny nose) or in eyedrops  redness
rebound congestion a problem with overuse

Found widely in OTC cold & flu medications
** Phenylephrine – main ingredient used in OTC meds
- Pseudoephedrine (Sudafed) (access restricted) ***
Used illegally to synthesize methamphetamine
- Naphazoline
- Tetrahydrozoline (Tyzine, Visine)
- Xylometazoline (Otrivin), Oxymetazoline (Afrin)

Pharm (14 decks)

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