Metoprolol: A Comprehensive Overview for Nurses

Nurse Beth, MSN

Providers write upwards of 45 million prescriptions for metoprolol annually⁽¹⁾. Nurses will encounter many patients on this drug, and this article will help you to administer metoprolol knowledgeably and safely.

Following this article, you will be able to:

Identify the mechanism of action of metoprolol
List the side effects of metoprolol
List the indications and contraindications of metoprolol
Identify key nursing considerations

Metoprolol has been in use for a long time. Developed in 1969 and approved by the FDA in 1978^(2),metoprolol treats hypertension, angina pectoris, and other cardiovascular conditions. Metoprolol is often used in combination with a thiazide-type diuretic to treat hypertension.

Metoprolol is not without serious risks. It carries an FDA black box warning. A large part of the risk is in abruptly discontinuing the drug. Sudden discontinuation of metoprolol can cause angina or even heart attack (myocardial infarction)⁽³⁾.

Metoprolol Warning

Mechanism of Action

Metoprolol is a beta1-selective (cardioselective) adrenergic receptor-blocking agent, or beta-blocker for short. Beta-blockers are so-called because they block and inhibit the effects of epinephrine, a stress hormone known as adrenaline. Epinephrine raises the heart rate and causes vasoconstriction, which increases blood pressure.

Metoprolol has the following actions⁽⁴⁾:

Decreases AV nodal conduction (negative chronotropic effect)
Reduces contractility (negative inotropic effect)
Relaxes blood vessels
Decreases myocardial oxygen demand
Decreases cardiac output
Reduces cardiac workload

As a result of those actions, metoprolol⁽⁴⁾:

Slows heart rate
Reduces blood pressure (antihypertensive effects)
Reduces mortality and reinfarction after myocardial infarction (heart attack)
Prevents angina (anti-anginal effects)

Pharmacology

Metoprolol is metabolized in the liver and excreted by the kidneys⁽⁴⁾.

Indications

Metoprolol is available in immediate-release (metoprolol tartrate) and extended-release (metoprolol succinate) formulations.

While both formulations treat cardiovascular conditions and have similar clinical effects, each has critical differences and indications. They are not interchangeable, and prescription errors mixing the two have resulted in death, including a well-known case study of a 65-year-old man who developed an atrioventricular block from receiving metoprolol tartrate instead of metoprolol succinate.

Immediate release: metoprolol tartrate (Lopressor)

Metoprolol tartrate is available in both tablet and IV form. Metoprolol tartrate is FDA-approved to treat:

angina
atrial fibrillation/flutter
hypertension
heart attack (myocardial infarction)

Off-label use includes:

supraventricular tachycardia (see more below)
thyroid storm

Metoprolol tartrate is not approved for use in heart failure. It may increase oxygen requirements and can worsen or precipitate failure

Extended release: metoprolol succinate (Toprol XL)

Metoprolol succinate is available in tablet form only and is FDA-approved to treat:

angina
atrial fibrillation/flutter
hypertension
heart failure

Metoprolol succinate is not approved to treat or prevent heart attacks.

Nursing Considerations

Bradycardia and hypotension are the two most serious side effects for nurses to consider. Monitor heart rate, rhythm, and blood pressure.
While bronchospasm is a less common side effect, beta-blockers are traditionally not prescribed to asthmatics or those with bronchospastic disease.
If you suspect your patient on metoprolol is hypoglycemic, do not rule it out because they are not tachycardic. Because metoprolol reduces heart rate, it can mask the tachycardia that typically occurs with hypoglycemia. The other symptoms of hypoglycemia, such as dizziness and diaphoresis, will be present. Get a fingerstick.
Metoprolol can cause bradycardia. Give atropine (0.25-0.5 mg) IVP if heart block or bradycardia occurs⁽⁴⁾.
Do not administer metoprolol to patients with severe bradycardia; heart block greater than first-degree, cardiogenic shock, or sick sinus syndrome without a pacemaker.
Do not administer metoprolol to patients with decompensated heart failure. While metoprolol is used to treat heart failure, it can worsen heart failure in patients with decompensation.
If you decide to hold the medication because the heart rate or blood pressure is low and there are no parameters for administration, notify the provider so they can adjust their treatment accordingly. Otherwise, providers will assume their patient received the medication and the treatment is working.
The risk of bradycardia increases with the concomitant use of glycosides, clonidine, diltiazem, and verapamil. Always review all of the medications your patient is taking.
Do not routinely withhold metoprolol before surgery. Contact the provider if your patient is scheduled for surgery and is NPO. Anticipate that the admitting provider or surgeon you call may refer you to the provider who ordered the metoprolol, such as the cardiologist.

Administration

Metoprolol is administered in both oral and IV forms.

Metoprolol tartrate: Oral

Oral dosage 100mg-400mg total daily, typically given twice a day
Administer with food or immediately following food intake
take blood pressure and heart rate before administering
Follow ordered parameters for heart rate and blood pressure
Contact the provider if there are no parameters ordered and the heart rate or blood pressure is low

Metoprolol tartrate: IV

IV dosage 2.5-5 mg bolus over 2 min, up to 3 doses
Used to achieve rate control in the acute setting for supraventricular tachydysrhythmias (SVT) such as uncontrolled atrial fibrillation/flutter (AFF) with rapid ventricular response
Requires cardiac monitored bed
Monitor heart rate, blood pressure, and heart rhythm
If IV Lopressor worked for the SVT, the provider will likely prescribe oral Lopressor once the patient is stable

Metoprolol succinate: Oral

Oral dosage 100mg-400mg given once daily
Give without regard to meals
Take blood pressure and heart rate before administering
Follow ordered parameters for heart rate and blood pressure
Contact the provider if there are no parameters ordered and the heart rate or blood pressure is low
Divide on scoreline if needed for dosage
Do not crush this or any extended-release medication for nasogastric administration or otherwi.se

Adverse Effects

The primary adverse effects of metoprolol include the following:

heart failure exacerbation
fatigue
depression
bradycardia or heart block
hypotension
bronchospasm
cold extremities
dizziness
decreased libido
diarrhea
tinnitus
decreased exercise capacity
glucose intolerance, and may mask hypoglycemia

Some side effects, such as dizziness, drowsiness, and fatigue, improve after a few days on the drug. Abrupt cessation of metoprolol may lead to angina or myocardial infarction. The risk is likely higher in those with underlying heart disease.

Contraindications

Metoprolol is contraindicated in patients with pulmonary bronchospastic disease, pheochromocytoma, severe bradycardia, and thyroid disease⁽⁴⁾.

Drug Interactions

Metoprolol can interact with digoxin (Lanoxin), clonidine, and calcium channel blockers as they slow heart rate. Monitor the heart rate and the PR interval^{(4, 5)}.

Concomitant use of catecholamine-depleting drugs, including reserpine and MAO inhibitors, can cause hypotension or bradycardia^{(4, 5)}. Monitor blood pressure and heart rate.

Metoprolol is known to interact with certain antidepressants⁽⁴⁾.

Patient Education

When discharging a patient from the hospital, include the time of the last dose given and the time of the next dose to be taken in the printed discharge instructions. Here are some additional key points for patient education:

Take Lopressor with or immediately following meals.
Take Toprol XL without regard to meals.
Do not crush or chew Toprol XL. Toprol XL tablets are scored. Tablets can be divided on the score line for correct dosage if needed.
Notify your provider if you have sudden weight gain or episodic shortness of breath
Call 911 or go to an emergency room if you have chest pain or difficulty breathing.
Stand up slowly to prevent a drop in blood pressure, known as orthostatic hypotension.
Check your heart rate and blood pressure regularly at home.
Do not stop taking your medication without the guidance of your healthcare provider; it could result in chest pain or even a heart attack.

Anecdotal Information

There's evidence-based practice, and there's also practice-based evidence. Practice-based evidence is a function of experience and clinical expertise. After many years of practice, nurses recognize patterns and synthesize information.

While having a cough as a side effect is not highlighted in the literature (although it's mentioned), a dry cough is a complaint I've heard from patients on beta-blockers. If bothersome enough, it can result in having to change medications.

Patients may complain of being short of breath and unable to get their heart rate up while exercising. One 65-year-old man said, "I felt like I lost my strength.” His heart simply does not beat as fast as before, and it's an uncomfortable adjustment.

From an experienced cardiac nurse and Staff Development Specialist point of view, it's alarming that some hospitals push nurses to administer IV metoprolol tartrate to patients with SVT on units with non-monitored beds. This practice happens even on units where nurses do not have basic arrhythmia skills or ACLS.

Patients requiring immediate IVP metoprolol tartrate to control their heart rate require close monitoring for safety. They should be transferred to a monitored bed in a unit with constant cardiac monitoring and experienced nurses. Be sure to know your facility's policies.

Key Takeaways

In conclusion, metoprolol is a beta-blocker and widely prescribed antihypertensive and anti-anginal medication. It is essential for nurses to be familiar with metoprolol, as they are likely to encounter patients taking this medication. In summary:

Beta-blockers block epinephrine's effects, a stress hormone that raises heart rate and blood pressure.
Metoprolol is available in two formulations, each with different indications.
Toprol XL is FDA-approved to treat angina, atrial fibrillation/flutter, hypertension, and heart failure.
Lopressor is FDA-approved to treat angina, atrial fibrillation/flutter, hypertension, and myocardial infarction.
Monitor heart rate, rhythm, and blood pressure, as serious side effects of metoprolol include bradycardia and hypotension.
Avoid metoprolol in patients with bronchospastic disease, including asthma.
Do not discontinue abruptly. Abrupt discontinuation of metoprolol can worsen chest pain, cause arrhythmias and increase the risk of myocardial infarctions.on

Nurses should know the mechanism of action, indications, contraindications, and nursing considerations of metoprolol to administer it knowledgeably and safely.

References

1. Agency for Healthcare Research and Quality. Number of people with purchase in thousands by prescribed drug, United States, 1996 to 2020. Medical Expenditure Panel Survey.

2. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury [Internet]. Bethesda (MD): National Institute of Diabetes and Digestive and Kidney Diseases; 2012-. Metoprolol. [Updated 2017 January 15]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547984/

3. Morris J, Dunham A. Metoprolol. [Updated 2022 October 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532923/

4. Novartis Lopressor package insert. Accessed via the internet January 12, 2023.https://www.accessdata.fda.gov/drugsatfda_docs/label/2008/017963s062,018704s021lbl.pdf

5. Farzam K, Jan A. Beta Blockers. [Updated 2022 July 21]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK532906

6. Molden E, Spigset O. Interaksjoner mellom metoprolol on antidepressive legemidler [Interactions between metoprolol and antidepressants]. Tidsskr Nor Laegeforen. 2011 Sep 20;131(18):1777-9. Norwegian. doi: 10.4045/tidsskr.11.0143. PMID: 21946596.

7. Toprol XL package insert. Accessed via the internet January 12, 2023.https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/019962s038lbl.pdf