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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
Epi - Blood Vessels
Epinephrine stimulates both a1 vasoconstriction b2 vasodilation Epinephrine is more potent at b2 than a1 NE = Epi at b1; Epi>NE at a1, Epi >>NE at b2 *** At high doses, a1 vasoconstriction predominates
26
Distribution and density of a & b receptors differs in different vascular beds
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
Epi - Smooth Muscle
``` 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
Epi - Glands
Lacrimation (a1 secretion) Sweating (palms) and piloerection (a1) Salivation - scant, mucous secretion Pancreas - blocks insulin release (a2 inhibit > b2 stimulate)
29
Epi - Metabolic Effects
Calorigenic effect Glycogenolysis and gluconeogenesis by liver (a1, b2) Lipolysis - increased free fatty acids (a1, b1, b2, b3) (a2 inhibit)
30
Epi - Clinical Uses
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
Epi - Other Uses
``` 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
Epi - Adverse Effects
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
Epi- Contraindications
Hypertension Shock (hypovolemic) - further compromised blood flow Hyperthyroidism Angina pectoris - increases O2 demand Asthmatics with degenerative heart disease
34
Norepinephrine (Levophed)
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
Norepinephrine administration and side effects
Administration: IV infusion to maintain blood pressure during spinal anesthesia or hypotensive shock. Side Effects: anxiety, slow forceful heart beat; headache
36
Isoproternol (Isuprel)
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
Other isoproternol effects
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
Dopamine (Intropin)
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
Dopamine Clinical uses
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
Dobutamine (Dobutrex)
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
alpha 1 -Adrenergic Agonists and mixed-acting alpha agonists
= Pressor Agents Phenylephrine (Neosynephrine) Prototype Methoxamine (Vasoxyl) Midodrine (Pro Amatine) Mixed Acting Alpha agonists Mephentermine (Wyamine sulfate) Metaraminol (Aramine)
42
Phenylephrine
prototype alpha-1 agonist Effects: vasoconstriction increase peripheral resistance; increase BP increased blood pressure causes reflex bradycardia (blocked by atropine)
43
Phenylephrine uses
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
beta-2 selective agonists
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
Albuterol (Proventil, Ventolin)
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
Other beta2 selective agonists
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
Indirectly Acting Sympathomimetics
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
Tyramine
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
Cocaine
Cocaine, tricyclic antidepressants (TCAs), and SNRIs competitively block NE reuptake into nerve terminal NE levels in synapse higher for longer periods
50
Amphetamines
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
Amphetamines in the CNS
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
Amphetamines - cardiovascular effects
vasoconstriction, increased heart rate | effects vary with dose and drug
53
clinical uses of amphetamines
Narcolepsy ADHD Obesity - depress appetite not metabolism; tolerance develops, usefulness is questionable
54
amphetamine toxicity
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
Ephedrine
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
Nasal Decongestants
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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