18.4: Beta-Adrenergic Blockers
By the end of this section, you should be able to:
- 18.4.1 Identify the characteristics of the beta-adrenergic blocker drugs used to treat hypertension.
- 18.4.2 Explain the indications, actions, adverse reactions, and interactions of the beta-adrenergic blocker drugs used to treat hypertension.
- 18.4.3 Describe nursing implications of beta-adrenergic blocker drugs used to treat hypertension.
- 18.4.4 Explain the client education related to beta-adrenergic blocker drugs used to treat hypertension.
Introduction and Use
Beta-adrenergic blockers (beta blockers) are a classification of drugs that inhibit chronotropic, inotropic, and vasoconstrictor response to catecholamine—such as epinephrine and norepinephrine—by exerting effects on adrenergic receptors beta 1, beta 2, and alpha.
Beta 1 receptors are found primarily in the heart and kidneys, and they increase the heart rate, myocardial activity, and release of renin. Beta 2 receptors are found in the smooth muscle tissue of the heart, lungs, and nervous system and increase myocardial contractility and cause muscle tremors. Alpha receptors stimulate vasoconstriction.
Beta blockers are classified as either nonselective or cardio-selective. Nonselective beta blockers affect both beta 1 and beta 2 and act on the cardiovascular and respiratory systems. Cardio-selective beta blockers, in contrast, affect beta 1, which impacts the cardiovascular system (Tucker et al., 2022).
Beta blockers decrease heart rate, decrease myocardial contractility, and decrease the rate of conduction through the atrioventricular (AV) node, thereby lowering blood pressure and heart rate. Beta blockers also cause vasodilation and decrease the release of renin and angiotensin II, promoting excretion of sodium and water from the body. Beta blockers are relatively safe for use. Beta blockers 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).
Most beta blockers are taken orally. Labetalol, metoprolol, and propranolol can be administered intravenously. Extended-release beta blockers should not be crushed. Nurses should monitor blood pressure and pulse rate of clients using beta blockers. Beta blockers should not be administered if the client is hypotensive or has a heart rate of less than 60 (Farzam & Jan, 2022).
Special Considerations
Beta Blockers
Beta blockers pose an ethical dilemma for health care providers because they cause anxiolytic effects. The FDA, however, does not support this use for beta blockers. The health care provider may prescribe beta blockers off-label (against FDA-approved labeling indications for drug use) for anxiety. Therefore, the prescribed use of beta blockers for anxiolysis should be weighed against standards of practice as well as risks and benefits to the client.
(Source: Shahrokhi & Gupta, 2023)
Beta blockers may mask low blood sugar levels in clients with diabetes due to sympathetic nervous system inhibition.
(Source: Dungan et al., 2019)
Asthmatic clients and clients with chronic lung diseases should be monitored carefully while taking beta blockers because lung function can decrease due to beta 2 inhibition.
(Source: Huang et al., 2021)
Table 18.7 lists common beta blockers and typical routes and dosing for adult clients.
| Drug | Routes and Dosage Ranges |
|---|---|
|
Atenolol
( Tenormin ) |
50 mg orally daily, either alone or with diuretic therapy. If optimal response is not achieved, the dosage should increase to 100 mg orally daily. Dosage beyond 100 mg a day is unlikely to produce any further benefit. |
|
Carvedilol
( Coreq ) |
6.25–25 mg orally twice daily; maximum dose 25 mg daily. |
|
Metoprolol tartrate
( Lopressor ) |
Initial dosage:
100 mg orally daily in single or divided doses. Increase dosage at weekly (or longer) intervals until optimum blood pressure reduction is achieved.
Effective dosage: 100–450 mg daily. |
|
Nadolol
( Corgard ) |
40–320 mg orally daily. |
|
Propranolol
( Inderal LA ) |
40 mg orally twice daily; maximum dose 640 mg daily. |
Adverse Effects and Contraindications
Adverse effects of beta blockers are 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.
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. People with diabetes should use beta blockers cautiously because they can mask the symptoms of hypoglycemia, causing confusion, fainting, or seizures.
Table 18.8 is a drug prototype table for beta-adrenergic blockers featuring metoprolol tartrate. 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
Initial dosage: 100 mg orally daily in single or divided doses. Increased dosage at weekly (or longer) intervals until optimum blood pressure reduction is achieved. Effective dosage: 100–450 mg daily. |
|
Indications
To control hypertension In the treatment of angina, acute myocardial infarction, and heart failure Therapeutic Effects Lowers blood pressure Decreases cardiac workload |
Drug Interactions
Albuterol Clonidine Mefloquine Calcium channel blockers Ma-huang Ephedra Black cohosh Hawthorne Food Interactions Caffeine Alcohol Tobacco Licorice |
|
Adverse Effects
Fatigue/weakness Dizziness Headache Hypotension Blurred vision Dry mouth Nausea/vomiting/diarrhea Drowsiness/insomnia Tinnitus Peripheral edema Erectile dysfunction |
Contraindications
Hypersensitivity AV block Cardiogenic shock Hypotension Acute heart failure Bradycardia Sick sinus syndrome Severe peripheral arterial circulatory disorders Caution: Thyroid impairment Hepatic impairment Asthma Peripheral vascular disease Diabetes mellitus Chronic obstructive pulmonary disease (COPD) Cerebrovascular disease |
Clinical Tip
Assessing Comorbidities: Asthma, Chronic Obstructive Pulmonary Disease, and Diabetes
Nurses should always assess a client’s comorbidities—such as asthma, COPD, and diabetes—before administering beta blocker drugs. To prevent a pharmacological drug interaction, the nurse must assess whether clients are taking short-acting beta agonists (SABAs) because beta blockers can reduce their effectiveness. Additionally, nurses should be aware that beta blockers can mask the symptoms of hypoglycemia in clients with diabetes.
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.
- Do not administer the drug if the client’s heart rate is less than 60 beats per minute and notify 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 before taking a beta-adrenergic blocker and do not administer the drug if the pulse is less than 60 beats/minute or as directed by their health care provider.
- Understand that beta-adrenergic blockers can induce hyperglycemia. Clients with diabetes should monitor blood glucose levels closely.
- 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.
The client taking a beta-adrenergic blocker should not:
- Take beta-adrenergic blockers with over-the-counter (OTC) drugs or herbal supplements such as ma-huang, ephedra, black cohosh, hawthorn, or licorice without consulting their health care provider because these supplements may interfere with the action of the beta-adrenergic blocker.
- Discontinue use without speaking with the health care provider first because this may cause exacerbation of angina and myocardial infarction.
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. Seek health care provider advice before discontinuing use.