1. Adrenergic-Blocking Drugs
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)
Have the opposite effect of adrenergic drugs
Inhibit—or lyse—sympathetic stimulation
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3. Adrenergic Blockers (cont’d)
Also known as:
Adrenergic antagonists
Sympatholytics
Alpha blockers, beta blockers, or alpha-beta blockers
Classified by the type of adrenergic receptor they block
Alpha1 and alpha2 receptors
Beta1 and beta2 receptors
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5. 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 benign prostatic hyperplasia (BPH)
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6. 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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7. Classroom Response Question
When phentolamine is used to diagnose the presence of pheochromocytoma, the nurse will assess for what indicative finding?
Rapid decrease in blood pressure
Steady increase in blood pressure
Slower heart rate
Reduced cardiac ectopy
Correct answer: A
Rationale: To help establish a diagnosis of pheochromocytoma, a single intravenous dose of phentolamine is given to the hypertensive patient who is suspected of having the tumor. If the blood pressure declines rapidly, it is highly likely that the patient has a pheochromocytoma.
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8. Alpha Blockers: Adverse Effects
Body System
Adverse Effects
Cardiovascular
CNS
Palpitations, orthostatic hypotension, tachycardia, edema, chest pain
Dizziness, headache, anxiety, depression, weakness, numbness, fatigue
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9. Alpha Blockers: Adverse Effects (cont’d)
Body System
Adverse Effects
Gastrointestinal
Other
Nausea, vomiting, diarrhea, constipation, abdominal pain Incontinence, dry mouth, pharyngitis
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10. Classroom Response Question
When administering an alpha blocker for the first time, it is most important for the nurse to assess the patient for the development of
renal failure.
hypotension.
blood dyscrasia.
dysrhythmias.
Correct answer: B
Rationale: The primary adverse effects of alpha blockers are those related to their effects on the vasculature. First-dose phenomenon, which is a severe and sudden drop in blood pressure after the administration of the first dose of an alpha-adrenergic blocker, can cause patients to fall or pass out. All patients must be warned about this adverse effect before they take their first dose of an alpha blocker. Orthostatic hypotension can occur with any dose of an alpha blocker, and patients must be warned to get up slowly from a supine position.
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Common Alpha Blockers
phenoxybenzamine HCl (Dibenzyline)
phentolamine (Regitine)
prazosin (Minipress)
terazosin (Hytrin)
alfuzosin (UroXatral)
tamsulosin (Flomax)
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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 sinoatrial (SA) node recovery
Slow conduction rate through the AV node
Decrease myocardial contractility, thus reducing myocardial oxygen demand
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15. 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
Decreases demand for myocardial oxygen
Cardioprotective
Inhibits stimulation from circulating catecholamines
Dysrhythmias
Class II antidysrhythmic
Migraine headache
Lipophilicity allows entry into CNS
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17. Classroom Response Question
A 58-year-old patient is recovering in the intensive care unit after a myocardial infarction (MI). The nurse notes an order for the beta blocker metoprolol (Lopressor). The purpose of this drug is to
dilate the coronary arteries.
inhibit stimulation of the myocardium by circulating catecholamines.
provide a positive inotropic effect.
maintain the patient’s blood pressure.
Correct answer: B
Rationale: Studies have shown increased survival in patients given metoprolol after experiencing an MI. Metoprolol has a cardioprotective effect by decreasing the heart’s response to circulating catecholamines resulting from the myocardial infarction.
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Indications (cont’d)
Antihypertensive
Heart failure
Glaucoma (topical use)
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19. Adverse Effects: Beta Blockers
Body System
Adverse Effects
Blood
Cardiovascular
CNS
Agranulocytosis, thrombocytopenia AV block, bradycardia, heart failure Dizziness, depression, unusual dreams, drowsiness
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20. Adverse Effects: Beta Blockers
Body System
Adverse Effects
Gastrointestinal Other
Nausea, vomiting, constipation, diarrhea Impotence, alopecia, wheezing, bronchospasm, dry mouth
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21. Adverse Effects: Beta Blockers (cont’d)
Nonselective beta blockers may interfere with normal responses to hypoglycemia (tremor, tachycardia, nervousness)
May mask signs and symptoms of hypoglycemia
Use with caution in patients with diabetes mellitus
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22. Classroom Response Question
The nurse knows that the adverse effects of a nonselective beta blocker are likely to be the most immediately life threatening in which patient?
Patient with type I diabetes
Patient with asthma
Patient with gastroesophageal reflux disease
Patient with hypertension
Correct answer: B
Rationale: While beta blockers may mask signs and symptoms of hypoglycemia, nonselective beta blockers may cause bronchoconstriction, which would be detrimental to the patient with asthma.
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23. Beta Blockers: Examples
atenolol (Tenormin)
carvedilol (Coreg)
esmolol (Brevibloc)
labetalol (Normodyne)
metoprolol (Lopressor)
propranolol (Inderal)
sotalol (Betapace)
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24. 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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25. 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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26. 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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27. 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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28. Adrenergic-Blocking Drugs: Nursing Implications (cont’d)
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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29. 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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30. Classroom Response Question
A patient with type 2 diabetes is taking a beta blocker as part of treatment for hypertension. Which complication is most likely to develop?
Hypertension
Hyperkalemia
Hypoglycemia
Angina
Correct answer: C
Rationale: Beta blockers may mask the signs and symptoms of hypoglycemia.
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Elsevier items and derived items © 2009, 2005, 2001 by Saunders, an imprint of Elsevier Inc.

31. 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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32. 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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