## Drug of Choice: Metoprolol for Post-MI Secondary Prevention ### Mechanism & Evidence Base Metoprolol is a selective β₁-adrenergic antagonist with proven mortality reduction in post-MI patients. Multiple landmark trials (COMMIT, CASIS) have demonstrated its efficacy in reducing reinfarction and sudden cardiac death when initiated early after acute MI. ### Key Advantages of Metoprolol in This Setting **Key Point:** Metoprolol has the strongest evidence base for mortality reduction in acute MI and post-MI management, particularly in patients with preserved ejection fraction. **High-Yield:** The COMMIT trial (2005) enrolled >45,000 acute MI patients and showed metoprolol reduced reinfarction and ventricular fibrillation. This trial is frequently referenced in NEET PG for post-MI beta-blocker selection. **Clinical Pearl:** Metoprolol's cardioselectivity (β₁ > β₂) at lower doses makes it safer in patients with mild COPD or asthma compared to non-selective agents. ### Comparison with Other Beta-Blockers | Agent | Selectivity | Post-MI Evidence | Special Feature | Preferred Use | | --- | --- | --- | --- | --- | | **Metoprolol** | β₁-selective | Strong (COMMIT, CASIS) | Rapid onset, short half-life | Post-MI, hypertension | | **Atenolol** | β₁-selective | Moderate | Long half-life, renal excretion | Stable angina, hypertension | | **Labetalol** | Mixed (α + β) | Weak | Vasodilatory, IV available | Hypertensive emergency | | **Carvedilol** | Non-selective + α | Moderate (HF-focused) | Antioxidant, HF indication | Heart failure, not first-line post-MI | **Warning:** Carvedilol, while excellent for heart failure with reduced ejection fraction, is NOT the first-line choice for post-MI secondary prevention in patients with normal ejection fraction. Its evidence base is stronger in systolic dysfunction. ### Dosing in Post-MI Metoprolol is typically initiated at 25–50 mg twice daily (oral) or 5 mg IV boluses (acute phase) and titrated to target heart rate of 50–60 bpm and systolic BP ≥90 mmHg. [cite:KD Tripathi 8e Ch 12]
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