Chapter 19 - The Red Zone

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CHAPTER 19
Adrenergic-Blocking Drugs
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Adrenergic Blockers


Bind to adrenergic receptors, but inhibit or
block stimulation of the sympathetic nervous
system (SNS)
Alpha-blockers and beta-blockers
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Adrenergic Blockers (cont’d)



Have the opposite effect of adrenergic drugs
Inhibit—or lyse—sympathetic stimulation
Also known as:

Adrenergic antagonists
 Sympatholytics
 Alpha-blockers, beta-blockers, or alpha-beta
blockers
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Adrenergic Blockers (cont’d)

Classified by the type of adrenergic receptor
they block

Alpha1 and alpha2 receptors
 Beta1 and beta2 receptors
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Drug Effects and Indications:
Alpha-Blockers
Cause both arterial and venous dilation,
reducing peripheral vascular resistance and
BP
 Used to treat hypertension
 Effect on receptors on prostate gland and
bladder decreases resistance to urinary
outflow, thus reducing urinary obstruction and
relieving effects of BPH

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Drug Effects and Indications:
Alpha-Blockers (cont’d)


Used to control and prevent hypertension in
patients with pheochromocytoma
Phentolamine


Quickly reverses the potent vasoconstrictive
effects of extravasated vasopressors such as
norepinephrine or epinephrine
Restores blood flow and prevents tissue necrosis
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Alpha-Blockers: Adverse Effects
Body System
Cardiovascular
Adverse Effects
Palpitations, orthostatic
hypotension, tachycardia,
edema, dysrhythmias, chest pain
CNS
Dizziness, headache, drowsiness,
anxiety, depression, vertigo,
weakness, numbness, fatigue
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Alpha-Blockers: Adverse Effects
(cont’d)
Body System
Gastrointestinal
Adverse Effects
Nausea, vomiting, diarrhea,
constipation, abdominal pain
Other
Incontinence, nosebleed,
tinnitus, dry mouth, pharyngitis,
rhinitis
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Common Alpha-Blockers




phenoxybenzamine HCl (Dibenzyline)
phentolamine (Regitine)
prazosin (Minipress)
tolazoline (Priscoline)
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Beta-Blockers




Block stimulation of beta receptors in
the SNS
Compete with norepinephrine and
epinephrine
Can be selective or nonselective
Nonselective beta-blockers block both beta1
and beta2 receptors
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Beta Receptors

Beta1 receptors



Located primarily on the heart
Beta-blockers selective for these receptors
are called cardioselective beta-blockers
Beta2 receptors

Located primarily on smooth muscle of
bronchioles and blood vessels
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Mechanism of Action

Cardioselective beta-blockers (beta1)





Reduce SNS stimulation of the heart
Decrease heart rate
Prolong SA node recovery
Slow conduction rate through the AV node
Decrease myocardial contractility, thus reducing
myocardial oxygen demand
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Mechanism of Action (cont’d)

Nonselective beta-blockers (beta1 and beta2)

Cause same effects on heart as cardioselective
beta-blockers
 Constrict bronchioles, resulting in narrowing of
airways and shortness of breath
 Produce vasoconstriction of blood vessels
 Other effects
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Indications

Angina


Cardioprotective


Inhibits stimulation from circulating
catecholamines
Dysrhythmias


Decreases demand for myocardial oxygen
Class II antidysrhythmic
Migraine headache

Lipophilicity allows entry into CNS
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Indications (cont’d)



Antihypertensive
Heart failure
Glaucoma (topical use)
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Adverse Effects: Beta-Blockers
Body System
Blood
Cardiovascular
CNS
Adverse Effects
Agranulocytosis, thrombocytopenia
AV block, bradycardia,
heart failure, peripheral vascular
insufficiency
Dizziness, mental depression,
lethargy, hallucinations, unusual
dreams
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Adverse Effects: Beta-Blockers
Body System
Gastrointestinal
Other
Adverse Effects
Nausea, dry mouth, vomiting,
diarrhea, cramps, ischemic
colitis
Impotence, rash, alopecia,
bronchospasm
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Adverse Effects: Beta-Blockers

Nonselective beta-blockers may interfere with
normal responses to hypoglycemia (tremor,
tachycardia, nervousness)

May mask signs and symptoms of hypoglycemia
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Beta-Blockers: Examples
acebutolol (Sectral)
 carvedilol (Coreg)
 labetalol (Normodyne)
 metoprolol (Lopressor)

atenolol (Tenormin)
 esmolol (Brevibloc)
 sotalol (Betapace)
 propranolol (Inderal)

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Adrenergic-Blocking Drugs:
Nursing Implications

Assess for allergies and history of COPD,
hypotension, cardiac dysrhythmias,
bradycardia, heart failure, or other
cardiovascular problems

Any preexisting condition that might be
exacerbated by the use of these drugs might be a
contraindication to their use
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Adrenergic-Blocking Drugs:
Nursing Implications (cont’d)


Remember that alpha-blockers may precipitate
hypotension
Remember that some beta-blockers may
precipitate bradycardia, hypotension,
heart block, heart failure, and
bronchoconstriction
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Adrenergic-Blocking Drugs:
Nursing Implications (cont’d)

Avoid over-the-counter medications because
of possible interactions

Possible drug interactions may occur with:


Antacids (aluminum hydroxide type)
Antimuscarinics/anticholinergics

Diuretics and cardiovascular drugs
 Neuromuscular blocking drugs
 Oral hypoglycemic drugs
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Adrenergic-Blocking Drugs:
Nursing Implications (cont’d)



Encourage patients to take medications
as prescribed
Instruct patients that these medications
should never be stopped abruptly
Inform patients to report constipation or the
development of urinary hesitancy or bladder
distention
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Adrenergic-Blocking Drugs:
Nursing Implications (cont’d)
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
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Teach patients to change positions slowly to
prevent or minimize postural hypotension
Instruct patients to avoid caffeine (excessive
irritability)
Instruct patients to avoid alcohol ingestion
and hazardous activities until blood levels
become stable
Instruct patients to notify their physician if
palpitations, dyspnea, nausea, or vomiting
occurs
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Adrenergic-Blocking Drugs:
Nursing Implications (cont’d)


Monitor for adverse effects
Monitor for therapeutic effects



Decreased chest pain in patients with angina
Return to normal BP and HR
Other specific effects, depending on the use
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Beta-Blocking Drugs:
Nursing Implications



Rebound hypertension or chest pain may occur if
this medication is discontinued abruptly
Instruct patients to notify their physician if they
become ill and unable to take medication
Inform patients that they may notice a decrease
in tolerance for exercise (dizziness and fainting
may occur with increased activity), and have
patients notify the physician if these problems
occur
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Beta-Blocking Drugs:
Nursing Implications (cont’d)

Inform patients to report the following to their
physician:





Weight gain of more than 2 pounds in 1 day or 5
pounds in 1 week
Edema of the feet or ankles
Shortness of breath
Excessive fatigue or weakness
Syncope or dizziness
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