19.3 Beta-Adrenergic Blockers

Learning Outcomes

By the end of this section, you should be able to:

• 19.3.1 Identify the characteristics of beta-adrenergic blocker drugs used to treat heart failure.
• 19.3.2 Explain the indications, actions, adverse reactions, and interactions of beta-adrenergic blocker drugs used to treat heart failure.
• 19.3.3 Describe nursing implications of beta-adrenergic blocker drugs used to treat heart failure.
• 19.3.4 Explain the client education related to beta-adrenergic blocker drugs used to treat heart failure.

As presented in Antihypertensive and Antianginal Drugs, beta-adrenergic blockers (beta blockers) are a classification of drugs that inhibit chronotropic, inotropic, and vasoconstrictor response to catecholamine, epinephrine, and norepinephrine. They do this by exerting effects on adrenergic receptors beta 1, beta 2, and alpha.

When the body is presented with a stressor, the sympathetic nervous system is activated. Catecholamines (norepinephrine and epinephrine) are released with the primary purpose of enhancing the fight-or-flight response. Catecholamines interact with beta-1, beta-2, and alpha receptors. Beta-1 receptors are found in the heart and kidneys, beta-2 receptors are found in cardiac tissue, and alpha receptors are found on arteries and veins.

Beta blockers can inhibit catecholamines from binding to beta-1, beta-2, and/or alpha receptors. This means that the sympathetic response (or the fight-or-flight response) is decreased. Part of the sympathetic response is to increase heart rate and contractility, increase blood pressure, and dilate bronchioles so that the body can run away or fight the threat. In general, beta blockers decrease heart rate and contractility, decrease blood pressure, and may cause some bronchoconstriction.

Select beta blockers have been found to decrease mortality in clients with heart failure (Heidenreich et al., 2022). Metoprolol and bisoprolol are two cardio-selective beta blockers, and carvedilol is a nonselective beta blocker that is used in the management of clients with heart failure.

Cardio-selective beta blockers affect the heart by reducing heart rate and contractility. Nonselective beta blockers affect the heart in the same way, but they also cause vasodilation due to their effects on alpha receptors of the arteries.

In heart failure, either cardio-selective beta blockers (bisoprolol, metoprolol succinate) or nonselective beta blockers (carvedilol) are used to decrease heart rate and contractility. Nonselective beta blockers also decrease blood pressure, which decreases afterload. If the heart rate is decreased, there is more time for diastole, or ventricular filling. Recall that coronary arteries deliver blood to the cardiac myocytes of the ventricles during diastole. This means that the ventricles themselves are getting more oxygen-rich blood. Also, if contractility is decreased, there is less demand for oxygen. Nonselective beta blockers also decrease afterload, which means the heart does not have to produce as much force to generate stroke volume.

Beta blockers are used to treat clients with hypertension, heart failure, arrhythmias, myocardial infarctions, migraines, glaucoma, and certain types of tremors. Beta blockers have also been used by health care providers as anxiolytics (to reduce anxiety).

Table 19.10 lists the beta blockers that are commonly used for heart failure and typical routes and dosing for adult clients. A complete list of beta blockers can be found in Antihypertensive and Antianginal Drugs.

Adverse Effects and Contraindications

Adverse effects of beta blockers include dizziness, fatigue, weight gain, constipation, cold hands and feet, hypercholesterolemia, shortness of breath, depression, nausea, dry mouth, and dry eyes. Serious adverse effects include bradycardia, arrhythmias, hypoglycemia, and hypotension. Rare side effects include sexual and erectile dysfunction.

Blood pressure and pulse rate should be monitored prior to administration. Beta blockers should not be administered if the client is hypotensive or has a heart rate less than 50–60 beats per minute, or as directed by the health care provider.

Nonselective beta blockers are contraindicated in clients with moderate to severe asthma and/or chronic lung diseases due to the potential for causing an exacerbation. Beta blockers should be used cautiously in clients with AV node and sinus bradycardia because they can aggravate these conditions. Beta blockers may exacerbate symptoms of Raynaud’s phenomenon or cause this disease process in clients. Clients with diabetes should use beta blockers cautiously because they can mask the symptoms of hypoglycemia, causing confusion, fainting, or seizures.

Safety Alert

Beta Blockers

Nonselective beta blockers should not be used in clients with asthma who are taking a short-acting beta agonist because they may cause worsening bronchospasm.

Beta blockers block aspects of the sympathetic nervous system, which is activated when blood sugar is too low. Beta blockers may mask symptoms of hypoglycemia.

Table 19.11 is a drug prototype table for beta blockers featuring metoprolol succinate. It lists drug class, mechanism of action, adult dosage, indications, therapeutic effects, drug and food interactions, adverse effects, and contraindications.

Drug Class Beta-adrenergic blocker Mechanism of Action Blocks beta-1 receptors, thereby decreasing cardiac workload by slowing the heart and decreasing the systolic blood pressure	Drug Dosage 12.5–200 mg orally daily; maximum dose: 200 mg daily.
Indications Hypertension Heart failure Angina Therapeutic Effects Lowers blood pressure Decreases cardiac workload	Drug Interactions Albuterol Clonidine Fluoxetine Mefloquine Paroxetine Propafenone Quinidine Food Interactions Caffeine Alcohol Tobacco
Adverse Effects Hypotension Bradycardia Fatigue/weakness Dizziness Headache Blurred vision Dry mouth Nausea/vomiting/diarrhea Drowsiness/insomnia Tinnitus Peripheral edema Erectile dysfunction	Contraindications Hypersensitivity AV block Sick sinus syndrome Cardiogenic shock Acute decompensated heart failure Severe bradycardia Caution: Thyroid impairment Hepatic impairment Asthma Peripheral vascular disease Diabetes mellitus Chronic obstructive pulmonary disease (COPD) Cerebrovascular disease

Table 19.11 Drug Prototype Table: Metoprolol Succinate (source: https://dailymed.nlm.nih.gov/dailymed/)

Clinical Tip

Assessing Comorbidities

As a nurse, it is important to assess a client’s comorbidities prior to administering drugs. When administering beta blockers, the nurse should assess whether the client has asthma or chronic obstructive pulmonary disease and is taking a short-acting beta agonist because this may cause a pharmacodynamics drug interaction.

Nursing Implications

The nurse should do the following for clients who are taking beta-adrenergic blockers:

• Assess the client’s blood pressure and pulse on an ongoing basis with initial dosing and intermittently during drug therapy. The beta-adrenergic blocker should be withheld if the client’s heart rate is less than 50–60 beats/minute or as directed by the health care provider.
• Assess and monitor the client for adverse effects, drug and food interactions, and contraindications.
• Provide client teaching regarding the drug and when to call the health care provider. See below for client teaching guidelines.

Client Teaching Guidelines

The client taking a beta-adrenergic blocker should:

• Take their pulse as directed prior to taking a beta-adrenergic blocker and do not administer the drug if the pulse is less than 50–60 beats/minute or as directed by their health care provider.
• Take this medication without regard to meals.
• Report side effects such as bradycardia, hypotension, fatigue, dizziness, constipation, or sexual dysfunction to their health care provider.
• Monitor for symptoms of worsening heart failure such as fatigue, weight gain, and peripheral edema.
• Monitor blood glucose levels closely because beta blockers can mask symptoms of hypoglycemia.
• Notify their health care provider about symptoms such as dizziness, lightheadedness, or fainting because these could be related to low blood pressure and/or low heart rate.

The client taking a beta-adrenergic blocker should not:

• Take beta-adrenergic blockers with OTC drugs or herbal supplements, such as ma-huang, ephedra, black cohosh, hawthorne, or licorice, without consulting their health care provider because these supplements may interfere with the action of the beta-adrenergic blocker.

FDA Black Box Warning

Beta-Adrenergic Blockers

Beta blocker therapy should not be abruptly stopped, but gradually tapered to avoid exacerbation of angina and myocardial infarction. Clients should seek health care provider advice prior to discontinuing use.