cardio:beta_blockers:start []

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====== Beta-Blockers ======

Beta-blockers antagonize beta-adrenergic receptors and reduce sympathetic stimulation of the cardiovascular system.

Primary Physiologic Effects:

• ↓ Heart rate  
• ↓ Contractility  
• ↓ Renin release  
• ↓ Cardiac output  
• ↓ Blood pressure  

Used in:

• [[cardio:hypertension:start|Hypertension]]  
• [[cardio:heart_failure:start|Heart Failure (HFrEF)]]  
• [[cardio:arrhythmias:start|Arrhythmias]]  
• [[cardio:angina:start|Angina]]  
• Post-myocardial infarction  

★ = Most commonly used / high-yield agents

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

β1 receptors:
• Heart (↑ HR, ↑ contractility)
• Kidney (↑ renin)

β2 receptors:
• Bronchi (bronchodilation)
• Vascular smooth muscle

Beta-blockers:

• Block β1 (cardiac effects)
• Some also block β2
• Some provide additional vasodilation (α1 or NO-mediated)

Reference: [[autonomics:start|Autonomic Receptors]]

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===== Generations of Beta-Blockers =====

==== 1st Generation – Nonselective (β1 + β2 Blockade) ====

Block both β1 and β2 receptors.

• ★ [[cardio:beta_blockers:propranolol|Propranolol]]
• [[cardio:beta_blockers:nadolol|Nadolol]]
• [[cardio:beta_blockers:timolol|Timolol]]
• [[cardio:beta_blockers:sotalol|Sotalol]]
• [[cardio:beta_blockers:penbutolol|Penbutolol]]
• [[cardio:beta_blockers:carteolol|Carteolol]]

Clinical Notes:

• Avoid in asthma / severe COPD  
• Sotalol also has Class III antiarrhythmic activity  

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==== 2nd Generation – Cardioselective (β1 Selective) ====

Primarily block β1 receptors.

• ★ [[cardio:beta_blockers:metoprolol|Metoprolol]]
• ★ [[cardio:beta_blockers:bisoprolol|Bisoprolol]]
• ★ [[cardio:beta_blockers:atenolol|Atenolol]]
• ★ [[cardio:beta_blockers:esmolol|Esmolol]] (IV, ultra short-acting)
• [[cardio:beta_blockers:nebivolol|Nebivolol]]
• [[cardio:beta_blockers:acebutolol|Acebutolol]]
• [[cardio:beta_blockers:betaxolol|Betaxolol]]
• [[cardio:beta_blockers:celiprolol|Celiprolol]]

Clinical Notes:

• Preferred in reactive airway disease  
• Selectivity is dose-dependent  
• Esmolol used in ICU / acute arrhythmias  

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==== 3rd Generation – Vasodilating Beta-Blockers ====

Provide additional vasodilation via α1 blockade or nitric oxide release.

Alpha/Beta Blockade:

• ★ [[cardio:beta_blockers:carvedilol|Carvedilol]]
• ★ [[cardio:beta_blockers:labetalol|Labetalol]]

Nitric Oxide–Mediated:

• ★ [[cardio:beta_blockers:nebivolol|Nebivolol]]

Less Common:

• [[cardio:beta_blockers:bucindolol|Bucindolol]]

Clinical Notes:

• Lower SVR in addition to HR reduction  
• Carvedilol reduces mortality in HFrEF  
• Labetalol commonly used in hypertensive emergencies  

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===== Beta-Blocker Comparison Table =====

^ Drug ^ Generation ^ Beta-1 Selective ^ Alpha-1 / Vasodilation ^ Lipophilic vs Hydrophilic ^ HFrEF Mortality Benefit ^ Common Uses ^
|[[cardio:beta_blockers:propranolol|Propranolol]] | 1st | No | No | Lipophilic | No | Migraine, tremor, portal HTN |
| [[cardio:beta_blockers:sotalol|Sotalol]] | 1st | No | No | Hydrophilic | No | AF, ventricular arrhythmias |
|[[cardio:beta_blockers:metoprolol|Metoprolol]] | 2nd | Yes | No | Lipophilic | Only Succinate | HTN, CAD, AF |
|[[cardio:beta_blockers:bisoprolol|Bisoprolol]] | 2nd | Yes | No | Moderate | Yes | HFrEF, HTN |
|[[cardio:beta_blockers:atenolol|Atenolol]] | 2nd | Yes | No | Hydrophilic | No | HTN (historical) |
|[[cardio:beta_blockers:esmolol|Esmolol]] | 2nd | Yes | No | Hydrophilic | No | ICU rate control |
|[[cardio:beta_blockers:carvedilol|Carvedilol]] | 3rd | No | Yes (alpha-1) | Lipophilic | Yes | HFrEF, HTN |
|[[cardio:beta_blockers:labetalol|Labetalol]] | 3rd | No | Yes (alpha-1) | Moderate | No | HTN emergency, pregnancy |
|[[cardio:beta_blockers:nebivolol|Nebivolol]] | 3rd | Yes | Nitric Oxide-Mediated | Lipophilic | No | HTN |
===== Intrinsic Sympathomimetic Activity (ISA) =====

Partial agonist activity:

• [[cardio:beta_blockers:pindolol|Pindolol]]
• [[cardio:beta_blockers:acebutolol|Acebutolol]]
• [[cardio:beta_blockers:penbutolol|Penbutolol]]

Less commonly used in modern practice.

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===== Evidence-Based Heart Failure Agents (Mortality Benefit) =====

• ★ [[cardio:beta_blockers:carvedilol|Carvedilol]]
• ★ [[cardio:beta_blockers:metoprolol|Metoprolol Succinate]]
• ★ [[cardio:beta_blockers:bisoprolol|Bisoprolol]]

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

Not all beta-blockers reduce mortality in HFrEF.

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===== Indications by Clinical Context =====

Hypertension:
• Not first-line for uncomplicated HTN  
• Preferred when CAD, arrhythmia, or HFrEF present  

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

Arrhythmias:
• Rate control in atrial fibrillation  
• SVT suppression  

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

Angina:
• Reduce myocardial oxygen demand  

→ [[cardio:angina:start|Anti-Anginal Module]]

Hypertensive Emergency:
• ★ [[cardio:beta_blockers:labetalol|Labetalol]]
• ★ [[cardio:beta_blockers:esmolol|Esmolol]]

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

• Bradycardia  
• AV block  
• Hypotension  
• Fatigue  
• Depression  
• Erectile dysfunction  
• Masked hypoglycemia  
• Bronchospasm (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  
• Severe peripheral vascular disease  

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

✔ Only certain agents reduce mortality in HFrEF  

✔ 1st gen = nonselective  

✔ 2nd gen = β1 selective  

✔ 3rd gen = vasodilating  

✔ Avoid abrupt discontinuation (rebound tachycardia)  

✔ Not first-line for uncomplicated hypertension  

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Related:

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