Metoprolol
Metoprolol is a selective beta-1 adrenergic blocker used in adults for hypertension, angina, post-myocardial infarction protection, heart failure with reduced ejection fraction and selected arrhythmias.
- Chemical formula
- C15H25NO3
- CAS number
- 51384-51-1
- ATC code
- C07AB02
- Molecular weight
- 267.36 g/mol
- Drug class
- Beta-1 selective adrenergic blocker
- Also known as
- H 93/26, Metoprolol
What is it?
Metoprolol is a cardioselective beta-1 adrenergic receptor blocker introduced in the 1970s. It is supplied as immediate-release tablets (typically as the tartrate salt) and as extended-release tablets (typically as the succinate salt). Both forms are dispensed only on prescription. Metoprolol succinate is approved in heart failure with reduced ejection fraction, while metoprolol tartrate is mainly used for hypertension, angina and rate control in arrhythmias.
Mechanism of action
Metoprolol selectively blocks beta-1 adrenergic receptors in the heart, reducing heart rate, contractility and atrioventricular conduction velocity, and lowering myocardial oxygen demand. At higher doses it can also block beta-2 receptors, which is relevant in respiratory disease. Metoprolol does not have intrinsic sympathomimetic activity. Long-term use in heart failure with reduced ejection fraction is associated with reverse remodelling and improved survival.
Pharmacokinetics
Metoprolol is rapidly absorbed orally, but undergoes substantial first-pass hepatic metabolism, mainly by CYP2D6, with bioavailability around 50%. Plasma protein binding is approximately 12%. The terminal half-life of immediate-release metoprolol is about three to seven hours, while the extended-release succinate form provides a more uniform plasma profile over 24 hours. Poor metabolisers of CYP2D6 have higher exposure and a stronger effect at the same dose.
Indications
Metoprolol is approved in adults for hypertension, chronic stable angina pectoris, supraventricular tachyarrhythmias and rate control in atrial fibrillation, post-myocardial infarction secondary prevention, prevention of migraine and, as the extended-release succinate, for heart failure with reduced ejection fraction. According to international guidelines, metoprolol is one of the recommended beta-blockers in heart failure, alongside bisoprolol and carvedilol.
Safety profile
Common adverse effects include fatigue, dizziness, bradycardia, cold extremities and gastrointestinal symptoms. Bronchospasm is uncommon at standard doses but can occur in patients with asthma or COPD because of partial beta-2 activity at higher doses. Sudden discontinuation can cause rebound tachycardia, hypertension or ischaemia. According to the prescribing information, the medication should be tapered gradually, particularly after long-term use, and used cautiously with other negative chronotropic agents.
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Frequently asked questions
What is the difference between metoprolol tartrate and succinate? ▾
Metoprolol tartrate is an immediate-release formulation usually given two to three times daily for hypertension, angina and rate control. Metoprolol succinate is an extended-release formulation given once daily and is the form approved for heart failure with reduced ejection fraction. According to the prescribing information, the two are not interchangeable on a milligram-for-milligram basis without dose adjustment, and switching should be supervised by the prescriber.
Can metoprolol be used in asthma or COPD? ▾
Metoprolol is cardioselective for beta-1 receptors, but selectivity diminishes at higher doses, and beta-2 blockade can trigger bronchospasm in susceptible patients. According to international guidelines, beta-blockers are not absolutely contraindicated in mild to moderate asthma or COPD when there is a strong cardiovascular indication, but careful titration with cardioselective agents and specialist supervision are recommended. Severe or unstable asthma remains a contraindication.
Why should metoprolol not be stopped abruptly? ▾
Abrupt discontinuation of metoprolol can cause rebound increases in heart rate, blood pressure and myocardial oxygen demand, with rare cases of myocardial infarction or arrhythmia, particularly in patients with ischaemic heart disease. According to the prescribing information, gradual tapering over one to two weeks is recommended, supervised by the prescriber. This is particularly important after long-term therapy or in elderly patients.
Does metoprolol affect heart failure outcomes? ▾
Yes, when used as the extended-release succinate form. Large randomised trials have shown that metoprolol succinate reduces mortality, hospitalisations and the rate of progression in heart failure with reduced ejection fraction. According to international guidelines, metoprolol succinate is one of the recommended evidence-based beta-blockers in this setting, with bisoprolol and carvedilol as alternatives. The dose is up-titrated gradually under medical supervision.
What are the main contraindications for metoprolol? ▾
Metoprolol is contraindicated in known hypersensitivity, in second or third-degree atrioventricular block without a pacemaker, in cardiogenic shock, in severe bradycardia and severe peripheral arterial disease, and in decompensated heart failure. Caution is required in unstable asthma, severe hepatic impairment, diabetes (where it can mask hypoglycaemia symptoms), and pregnancy. According to the prescribing information, the medical history must be reviewed by a clinician before any prescription.
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