Chapter 19 Adrenergic-Blocking Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Chapter 19

Adrenergic-Blocking Drugs

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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

Adrenergic Blockers

2Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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

Adrenergic Blockers (cont’d)


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)

Drug Effects and Indications: Alpha Blockers


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

Drug Effects and Indications: Alpha Blockers (cont’d)


Classroom Response Question

When phentolamine is used to diagnose the presence of pheochromocytoma, the nurse will assess for what indicative finding?

A.Rapid decrease in blood pressure

B.Steady increase in blood pressure

C.Slower heart rate

D.Reduced cardiac ectopy


Alpha Blockers: Adverse Effects

Body System

Cardiovascular

CNS

Adverse EffectsPalpitations, orthostatichypotension, tachycardia, edema, chest pain

Dizziness, headache, anxiety, depression, weakness, numbness, fatigue

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 8

Alpha Blockers: Adverse Effects (cont’d)

Body System

Gastrointestinal

Other

Adverse EffectsNausea, vomiting, diarrhea, constipation, abdominal pain

Incontinence, dry mouth, pharyngitis



When administering an alpha blocker for the first time, it is most important for the nurse to assess the patient for the development of

A.renal failure.

B.hypotension.

C.blood dyscrasia.

D.dysrhythmias.


phenoxybenzamine HCl (Dibenzyline) phentolamine (Regitine) prazosin (Minipress) terazosin (Hytrin) alfuzosin (UroXatral) tamsulosin (Flomax)

Common Alpha 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

Beta Blockers


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

Beta Receptors


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

Mechanism of Action


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

Mechanism of Action (cont’d)


Angina Decreases demand for myocardial oxygen

Cardioprotective Inhibits stimulation from circulating catecholamines

Dysrhythmias Class II antidysrhythmic

Migraine headache Lipophilicity allows entry into CNS

Indications


Classroom Response QuestionA 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

A.dilate the coronary arteries.

B.inhibit stimulation of the myocardium by circulating catecholamines.

C.provide a positive inotropic effect.

D.maintain the patient’s blood pressure.


Antihypertensive Heart failure Glaucoma (topical use)

Indications (cont’d)


Adverse Effects: Beta Blockers

Body System

Blood

Cardiovascular

CNS

Adverse EffectsAgranulocytosis, thrombocytopenia

AV block, bradycardia, heart failure

Dizziness, depression, unusual dreams, drowsiness


Adverse Effects: Beta Blockers

Body System

Gastrointestinal

Other

Adverse EffectsNausea, vomiting, constipation, diarrhea

Impotence, alopecia, wheezing, bronchospasm, dry mouth


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

Adverse Effects: Beta Blockers (cont’d)



The nurse knows that the adverse effects of a nonselective beta blocker are likely to be the most immediately life threatening in which patient?

A.Patient with type I diabetes

B.Patient with asthma

C.Patient with gastroesophageal reflux disease

D.Patient with hypertension


atenolol (Tenormin) carvedilol (Coreg)

esmolol (Brevibloc) labetalol

(Normodyne)

Beta Blockers: Examples


metoprolol (Lopressor)

propranolol (Inderal)

sotalol (Betapace)

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

Adrenergic-Blocking Drugs: Nursing Implications


Remember that alpha blockers may precipitate hypotension

Remember that some beta blockers may precipitate bradycardia, hypotension, heart block, heart failure, and bronchoconstriction

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



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



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



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




A patient with type 2 diabetes is taking a beta blocker as part of treatment for hypertension. Which complication is most likely to develop?

A.Hypertension

B.Hyperkalemia

C.Hypoglycemia

D.Angina


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

Beta-Blocking Drugs: Nursing Implications


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

Beta-Blocking Drugs: Nursing Implications (cont’d)


Chapter 19 Adrenergic-Blocking Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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