Download Chapter 18 - The RedZone

CHAPTER 18
Adrenergic Drugs
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Adrenergic Drugs

Drugs that stimulate the sympathetic nervous
system (SNS)
 Also known as:


Adrenergic agonists
Sympathomimetics
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Characteristics

Mimic the effects of SNS neurotransmitters
(catecholamines)

Norepinephrine (NE)
 Epinephrine (EPI)
 Dopamine
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Adrenergic Receptors


Located throughout the body
Are receptors for the sympathetic
neurotransmitters



Alpha-adrenergic receptors
Beta-adrenergic receptors
Dopaminergic receptors: respond only to
dopamine
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Alpha-Adrenergic Receptors


Divided into alpha1 and alpha2 receptors
Differentiated by their location on nerves
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Alpha1-Adrenergic Receptors

Located on postsynaptic effector cells
(the cell, muscle, or organ that the nerve
stimulates)
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Alpha2-Adrenergic Receptors


Located on presynaptic nerve terminals
(the nerve that stimulates the effector cells)
Control the release of neurotransmitters
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Alpha-Adrenergic Agonist
Responses


Vasoconstriction
CNS stimulation
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Beta-Adrenergic Receptors

All are located on postsynaptic effector cells


Beta1-adrenergic receptors—located primarily
in the heart
Beta2-adrenergic receptors—located in smooth
muscle of the bronchioles, arterioles, and visceral
organs
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Beta-Adrenergic Agonist
Responses



Bronchial, GI, and uterine smooth muscle
relaxation
Glycogenolysis
Cardiac stimulation
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Dopaminergic Receptors



An additional adrenergic receptor
Stimulated by dopamine
Causes dilation of the following blood
vessels, resulting in increased blood flow




Renal
Mesenteric
Coronary
Cerebral
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Responses to Stimulation
Location
Cardiovascular
Receptor
Response
Blood vessels
Cardiac muscle
alpha1
beta2
beta1
AV Node
beta1
SA Node
beta1
Constriction
Dilation
Increased
contractility
Increased
heart rate
Increased
heart rate
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Responses to Stimulation
(cont’d)
Location
Gastrointestinal
Receptor
Response
Muscle
beta2 and alpha
Sphincters
alpha1
Decreased
motility
Constriction
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Responses to Stimulation
(cont’d)
Location
Genitourinary
Receptor
Response
Bladder
sphincter
Penis
Uterus
alpha1
Constriction
alpha1
alpha1
beta2
Ejaculation
Contraction
Relaxation
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Responses to Stimulation
(cont’d)
Location
Respiratory
Receptor
Response
Bronchial
muscles
beta2
Dilation
Liver
beta2
Glycogenolysis
Pupils
alpha1
Dilation
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Catecholamines


Substances that can produce a
sympathomimetic response
Endogenous


Epinephrine, norepinephrine, dopamine
Synthetic

Dobutamine, phenylephrine
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Mechanism of Action

Direct-acting sympathomimetic

Binds directly to the receptor and causes a
physiologic response
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Mechanism of Action (cont’d)

Indirect-acting sympathomimetic


Causes release of catecholamine from storage
sites (vesicles) in nerve endings
Catecholamine then binds to receptors and
causes a physiologic response
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Mechanism of Action (cont’d)

Mixed-acting sympathomimetic


Directly stimulates the receptor by binding
to it
and
Indirectly stimulates the receptor by causing
the release of stored neurotransmitters from
vesicles in the nerve endings
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Drug Effects

Stimulation of alpha-adrenergic receptors on
smooth muscles results in

Vasoconstriction of blood vessels
 Relaxation of GI smooth muscles (decreased
motility)
 Constriction of bladder sphincter
 Contraction of uterus
 Male ejaculation
 Contraction of pupillary muscles of the eye
(dilated pupils)
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Drug Effects (cont’d)

Stimulation of beta1-adrenergic receptors on
the myocardium, AV node, and SA node
results in cardiac stimulation
Increased force of contraction (positive inotropic
effect)
 Increased heart rate (positive chronotropic
effect)
 Increased conduction through AV node (positive
dromotropic effect)

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Drug Effects (cont’d)

Stimulation of beta2-adrenergic receptors on
the airways results in


Bronchodilation (relaxation of the bronchi)
Other effects of beta2-adrenergic stimulation
Uterine relaxation
 Glycogenolysis in the liver
 Increased renin secretion in the kidneys
 Relaxation of GI smooth muscles (decreased
motility)

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Indications

Treatment of asthma and bronchitis


Bronchodilators: drugs that stimulate beta2adrenergic receptors of bronchial smooth
muscles, causing relaxation, resulting in
bronchodilation
Examples: albuterol, ephedrine, epinephrine,
formoterol, levalbuterol, metaproterenol,
pirbuterol, salmeterol, and terbutaline*
* Used to stop premature labor—causes relaxation of uterine smooth
muscle
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Indications (cont’d)

Reduction of intraocular pressure and dilation
of pupils: treatment of open-angle glaucoma


Alpha-adrenergic receptors
Examples: epinephrine and dipivefrin
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Indications (cont’d)

Temporary relief of conjunctival congestion
(eyes)


Alpha-adrenergic receptors
Examples: epinephrine, naphazoline,
phenylephrine, tetrahydrozoline
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Indications (cont’d)

Treatment of nasal congestion

Intranasal (topical) application causes constriction
of dilated arterioles and reduction of nasal blood
flow, thus decreasing congestion
 Alpha1-adrenergic receptors
 Examples: epinephrine, ephedrine, naphazoline,
oxymetazoline, phenylephrine, and
tetrahydrozoline
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Vasoactive Adrenergics
(Pressors, Inotropes)
Also called cardioselective sympathomimetics
 Used to support the heart during cardiac
failure or shock; various alpha and beta
receptors affected

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Vasoactive Sympathomimetics
(Pressors, Inotropes): Examples
Dobutamine
 Ephedrine
 Fenoldopam
 Methoxamine
 Others

Dopamine
 Epinephrine
 Phenylephrine
 Norepinephrine

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Alpha-Adrenergic Adverse
Effects

CNS


Cardiovascular


Headache, restlessness, excitement, insomnia,
euphoria
Palpitations (dysrhythmias), tachycardia,
vasoconstriction, hypertension
Other

Loss of appetite, dry mouth, nausea, vomiting,
taste changes (rare)
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Beta-Adrenergic Adverse Effects

CNS


Cardiovascular


Mild tremors, headache, nervousness, dizziness
Increased heart rate, palpitations (dysrhythmias),
fluctuations in BP
Other

Sweating, nausea, vomiting, muscle cramps
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Interactions

Anesthetic drugs

Tricyclic antidepressants

MAOIs

Antihistamines
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Interactions (cont’d)

Thyroid preparations

Antihypertensives

Will directly antagonize another adrenergic
drug, resulting in reduced effects
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Nursing Implications

Assess for allergies and history of
hypertension, cardiac dysrhythmias, or other
cardiovascular disease

Assess renal, hepatic, and cardiac function
before treatment
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Nursing Implications (cont’d)

Perform baseline assessment of vital signs,
peripheral pulses, skin color, temperature,
and capillary refill; include postural blood
pressure and pulse

Follow administration guidelines carefully
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Nursing Implications (cont’d)

Intravenous administration

Check IV site often for infiltration
 Use clear IV solutions
 Use an infusion pump
 Infuse drug slowly to avoid dangerous
cardiovascular effects
 Monitor cardiac rhythm
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Nursing Implications (cont’d)

With chronic lung disease

Instruct patients to avoid factors that exacerbate
their condition

Encourage fluid intake (up to 3000 mL/day) if
permitted

Educate patients about proper dosing, use of
equipment (MDI, spacer, nebulizer), and
equipment care
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Nursing Implications (cont’d)

Salmeterol is indicated for prevention of
bronchospasms, not management of acute
symptoms

Overuse of nasal decongestants may cause
rebound nasal congestion or ulcerations

Avoid over-the-counter or other medications
because of possible interactions
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Nursing Implications (cont’d)

Administering two adrenergic drugs together
may precipitate severe cardiovascular effects
such as tachycardia or hypertension
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Nursing Implications (cont’d)

Monitor for therapeutic effects
(cardiovascular uses)

Decreased edema
 Increased urinary output
 Return to normal vital signs
 Improved skin color and temperature
 Increased LOC
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Nursing Implications (cont’d)

Monitor for therapeutic effects (asthma)

Return to normal respiratory rate
 Improved breath sounds, fewer crackles
 Increased air exchange
 Decreased cough
 Less dyspnea
 Improved blood gases
 Increased activity tolerance
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