====== Metoprolol ======

Metoprolol is a 2nd-generation, β1-selective beta-blocker.

It primarily blocks cardiac β1 receptors with minimal β2 activity at usual doses.

Classification:
• 2nd Generation (Cardioselective)
• No intrinsic sympathomimetic activity (ISA)

→ [[cardio:beta_blockers:start|Beta-Blockers Overview]]

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===== Available Formulations =====

Metoprolol exists in TWO forms:

1. Metoprolol Tartrate (Immediate-release)

2. Metoprolol Succinate (Extended-release)

These are NOT interchangeable.

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===== Mechanism of Action =====

Blocks β1 receptors:

• ↓ Heart rate
• ↓ Contractility
• ↓ AV nodal conduction
• ↓ Renin release

Net Effects:

• ↓ Cardiac output
• ↓ Blood pressure
• ↓ Myocardial oxygen demand

Cardioselectivity is dose-dependent.

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===== Indications =====

==== Hypertension ====

• Not first-line for uncomplicated HTN
• Useful when CAD, arrhythmia, or HFrEF present

→ [[cardio:hypertension:start|Hypertension Module]]

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==== Coronary Artery Disease / Post-MI ====

• Reduces mortality post-MI
• Decreases myocardial oxygen demand

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==== Arrhythmias ====

• Rate control in atrial fibrillation
• SVT suppression

→ [[cardio:arrhythmias:start|Dysrhythmias Module]]

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==== Heart Failure (HFrEF) ====

ONLY:
• ★ Metoprolol Succinate

has proven mortality benefit.

→ [[cardio:heart_failure:start|Heart Failure Module]]

Metoprolol tartrate does NOT have established mortality data in HFrEF.

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===== Tartrate vs Succinate =====

Metoprolol Tartrate:
• Immediate-release
• Usually dosed twice daily
• Common in inpatient setting
• Used for acute rate control

Metoprolol Succinate:
• Extended-release
• Once daily dosing
• Mortality benefit in HFrEF
• Preferred outpatient formulation

Exam Pearl:
If question involves heart failure mortality → choose succinate.

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===== Adverse Effects =====

• Bradycardia
• AV block
• Hypotension
• Fatigue
• Depression
• Erectile dysfunction
• Masked hypoglycemia

Less bronchospasm risk than nonselective agents.

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===== Contraindications =====

• Severe bradycardia
• High-grade AV block (without pacemaker)
• Cardiogenic shock
• Acute decompensated heart failure

Use caution in:
• Asthma (though safer than nonselective agents)
• Diabetes

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===== Clinical Pearls =====

✔ Cardioselective (β1 selective)  
✔ Succinate reduces mortality in HFrEF  
✔ Tartrate used more for acute rate control  
✔ Dose-dependent loss of selectivity  
✔ Not first-line for uncomplicated hypertension  

For other HF mortality agents see:

→ [[cardio:beta_blockers:carvedilol|Carvedilol]]
→ [[cardio:beta_blockers:bisoprolol|Bisoprolol]]

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Related:

→ [[cardio:beta_blockers:start|Beta-Blockers Overview]]
→ [[cardio:heart_failure:start|Heart Failure Module]]
→ [[cardio:arrhythmias:start|Dysrhythmias Module]]
→ [[cardio:hypertension:start|Hypertension Module]]
→ [[cardio:intro:start|Return to Cardiovascular Modules]]