Why is metoprolol (beta blocker) preferred over other beta blockers post myocardial infarction (MI)?

From the Guidelines

Metoprolol is the preferred beta blocker post-myocardial infarction (MI) due to its established efficacy in reducing mortality and preventing recurrent cardiac events, as evidenced by the 2017 AHA/ACC clinical performance and quality measures for adults with ST-elevation and non-ST-elevation myocardial infarction 1. The typical regimen starts with metoprolol tartrate 25-50 mg orally twice daily during the acute phase, transitioning to metoprolol succinate (extended-release) 25-200 mg once daily for long-term therapy, with the dose titrated based on heart rate and blood pressure response. Some key points to consider when using metoprolol post-MI include:

• Metoprolol is cardioselective, primarily blocking beta-1 receptors in the heart while having less effect on beta-2 receptors in the lungs and blood vessels, making it safer for patients with comorbid conditions like mild to moderate COPD or peripheral vascular disease.
• It has robust clinical trial evidence specifically in post-MI settings, with landmark studies demonstrating significant reductions in mortality, reinfarction, and sudden cardiac death.
• Metoprolol has favorable pharmacokinetics with predictable metabolism, moderate lipophilicity that balances CNS side effects and efficacy, and is available in both immediate and extended-release formulations for flexible dosing options.
• The AHA/ACC guidelines recommend using beta blockers without intrinsic sympathomimetic activity, and in patients with MI complicated with systolic cardiomyopathy with or without heart failure, one of the three proven beta blockers should be used: carvedilol, sustained-release metoprolol succinate, or bisoprolol 1.
• The choice of beta blocker for an individual patient is based primarily on pharmacokinetic and side effect criteria, as well as on physician familiarity, with metoprolol being a well-established first-line beta blocker for post-MI patients 1.

From the FDA Drug Label

Myocardial Infarction In a large (1,395 patients randomized), double-blind, placebo-controlled clinical study, metoprolol was shown to reduce 3-month mortality by 36% in patients with suspected or definite myocardial infarction The precise mechanism of action of metoprolol in patients with suspected or definite myocardial infarction is not known.

Metoprolol is given post MI compared to other beta blockers because it has been shown to reduce 3-month mortality by 36% in patients with suspected or definite myocardial infarction 2. The precise mechanism of action is not known, but it is thought to be related to its beta 1-selective (cardioselective) adrenergic receptor blocking activity 2. Key points include:

• Reduction in heart rate and cardiac output at rest and upon exercise
• Reduction of systolic blood pressure upon exercise
• Inhibition of isoproterenol-induced tachycardia
• Reduction of reflex orthostatic tachycardia The clinical studies demonstrate that metoprolol is effective in reducing mortality and improving outcomes in patients with myocardial infarction, making it a preferred choice over other beta blockers 2.

From the Research

Rationale for Metoprolol Post MI

• Metoprolol is often prescribed post-myocardial infarction (MI) due to its beta-blocking properties, which help reduce the heart's workload and lower blood pressure 3.
• A study comparing metoprolol and carvedilol in patients with acute MI found that overall survival was similar between the two groups, but carvedilol may be superior in patients with left ventricular ejection fraction ≤40% 3.
• Another study found that beta-blockers, including metoprolol, have become a cornerstone in the treatment of systolic heart failure, reducing all-cause death by 34-5% 4.

Comparison with Other Beta Blockers

• A meta-analysis comparing carvedilol with beta 1 selective beta-blockers (atenolol, bisoprolol, metoprolol, and nebivolol) found that carvedilol significantly reduced all-cause mortality in systolic heart failure patients 5.
• Bisoprolol has been shown to be effective in treating myocardial infarction with cardiac insufficiency, improving cardiac function and reducing serum homocysteine and C-reactive protein levels 6.
• The choice of beta-blocker is important, as benefit is not a class-effect, and some beta-blockers (e.g. xamoterol, bucindolol, nebivolol) may have diminished efficacy due to intrinsic sympathomimetic activity 4.

Key Considerations

• The dosage of metoprolol is important, with patients in the >12.5% to 25% dose category having improved survival compared to other dose categories 3.
• Left ventricular ejection fraction is a key factor in determining the effectiveness of metoprolol versus carvedilol, with carvedilol being superior in patients with left ventricular ejection fraction ≤40% 3.
• Adverse reactions associated with beta-blockers, including metoprolol, are mainly related to beta-2 blockade and alpha-blockade, and can include metabolic disturbance, bronchospasm, and sexual dysfunction 4.