Metoprolol is often prescribed, and medication must pay attention to these 3 points!

Clinical decision-making can be simpler.

01 Black box warning

1.1

Warning: Ischemic heart disease[1]

After abrupt discontinuation of certain β blockers, patients experience worsening of angina and, in some cases, myocardial infarction. Patients taking metoprolol succinate extended-release tablets for a long time, especially those with ischemic heart disease, should gradually reduce the dose within 1-2 weeks and the patient should be carefully monitored.

If angina is significantly worse or acute coronary insufficiency occurs, the administration of metoprolol succinate extended-release tablets should be resumed immediately, at least temporarily, and other measures appropriate for the treatment of unstable angina should be taken.

Patients are warned not to interrupt or stop treatment without medical advice. Since coronary artery disease is common and may go undetected, do not abruptly stop treatment with metoprolol succinate extended-release tablets, even in patients who are treated only for hypertension.

02 Contraindications

Metoprolol is contraindicated in people who are allergic to metoprolol and related derivatives or any excipients, who are allergic to other β blockers (cross-sensitivity between β receptor blockers may occur).

Metoprolol is banned from [2,3]:

heart rate

Second and third degree heart block;

Pronounced primary cardiac block (P-R interval≥ 0.24 sec);

Systolic blood pressure

or in patients with moderate to severe heart failure.

When using dimetolol for the treatment of hypertension and angina, this product is contraindicated in patients with sinus bradycardia, cardiac block of the first grade or higher, cardiogenic shock and marked heart failure, pathological sinus syndrome (unless a permanent pacemaker is installed), and severe peripheral arterial circulation disorders [1].

03 Precautions[1-3]

▎3.1 Heart failure

β receptor blockers, such as metoprolol, can cause decreased myocardial contractility and may induce heart failure and cardiogenic shock. If signs or symptoms of heart failure develop, treat the patient according to recommended guidelines. It may be necessary to reduce the dose of metoprolol or discontinue the drug.

Exacerbation of heart failure may occur during the administration of metoprolol succinate extended-release tablets. If the above symptoms occur, the diuretic dose should be increased first, and then the dose of metoprolol succinate extended-release tablets should be increased.

It may be necessary to reduce the dose of metoprolol succinate extended-release tablets or temporarily discontinue them. Such events do not preclude the subsequent rational application of metoprolol succinate extended-release tablets.

▎ 3.2 Ischemic heart disease

Patients with coronary artery disease should not abruptly discontinue metoprolol. Severe exacerbations of angina, myocardial infarction, and ventricular arrhythmias have been reported in patients with coronary artery disease following abrupt cessation of treatment with β receptor blockers.

In particular, when long-term use of metoprolol is discontinued in patients with coronary artery disease, the dose should be gradually reduced within 1-2 weeks and the patient should be carefully monitored.

▎3.3 Use during major surgery

Long-term routine β blockers should not be discontinued prior to major surgery. But impaired heart responsiveness to reflex adrenaline stimulation may increase the risk of general anesthesia and surgery.

Avoid the use of high-dose metoprolol extended-release tablets in patients undergoing non-cardiac surgery, as the use of this drug in patients with cardiovascular risk factors can lead to adverse effects such as bradycardia, hypotension, stroke, and death.

▎3.4 Bradycardia

With metoprolol, bradycardia including sinus apnea, heart block, and cardiac arrest has occurred. Patients with grade I AV block, sinus node dysfunction, or conduction disorders may be at increased risk.

The heart rate and rhythm of patients receiving metoprolol should be monitored. If severe bradycardia occurs, the dose should be reduced or metoprolol discontinued.

▎3.5 Exacerbation of bronchospasm disease

Patients with bronchospasm disease should generally not receive β receptor blockers, including metoprolol. However, due to its relative β1 selectivity, metoprolol can be used in patients with bronchospasm who do not respond to or cannot tolerate other antihypertensive therapies.

Since β1 selectivity is not absolute, use the lowest possible dose of metoprolol and consider a metoprolol administration regimen of small doses 3 times a day instead of a large dose of metoprolol 2 times a day to avoid producing higher plasma levels associated with longer dose intervals. Bronchodilators, including beta2 agonists, should be readily available or may be administered simultaneously.

▎ 3.6 Diabetes and hypoglycemia

β receptor blockers may mask tachycardia caused by hypoglycemia, but may not significantly affect other manifestations such as dizziness and sweating.

▎3.7 Pheochromocytoma

If metoprolol is used in the treatment of pheochromocytoma, it should be used in combination with α receptor blockers and only after the use of α receptor blockers. Due to the weakening of β-mediated vasodilation in skeletal muscle, patients with pheochromocytoma alone have associated β receptor blockers with abnormally elevated blood pressure.

▎ 3.8 Thyrotoxicosis

Metoprolol may mask certain clinical signs of hyperthyroidism (eg, tachycardia). Avoid abrupt discontinuation of β blockers, which may trigger thyroid storms.

▎3.9 Risk of allergic reactions

There is a risk of allergic reactions. Patients with a history of severe allergic reactions to various allergens may be more sensitive to repeated irritation (accidental, diagnostic, or therapeutic) when taking β receptor blockers. Such patients may not respond to the usual doses of epinephrine, which are commonly used to treat allergic reactions.

▎3.10 Information for patients

Advised patients:

Avoid operating cars and machines or doing other work that requires vigilance until determining the patient's response to metoprolol treatment;

If you have difficulty breathing, contact your doctor;

Inform the doctor or dentist before any type of surgery that the patient is taking metoprolol.

▎3.11 Liver damage

Consider starting treatment with metoprolol succinate extended-release tablets at doses lower than recommended for a given indication, gradually increasing the dose to optimize treatment while closely monitoring adverse events.

▎3.12 Peripheral vascular disease

β-blockers can induce or worsen symptoms of arterial insufficiency in patients with peripheral vascular disease.

▎3.13 Calcium channel blocker

Patients treated with β receptor blockers and calcium channel blockers such as verapamil and diltiazem have significant muscle strength and time-varying effects, caution should be exercised in patients treated with these drugs simultaneously.

Resources:

[1] Product Information: METOPROLOL SUCCINATE tablet, extended release, TWi Pharmaceuticals, Inc., Updated June 16, 2020

[2] Product Information: METOPROLOL TARTRATE injection, solution, Almaject, Inc., Updated March 27, 2020

[3] Product Information: METOPROLOL TARTRATE tablet, film coated, Advagen Pharma Limited, Updated July 26, 2021

Source: Clinical Pharmacy Channel of the Medical Community

Editor-in-charge: Xu Liyan

Proofreader: Zang Hengjia

Plate making: Xue Jiao