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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:
• Hypertension • Heart Failure (HFrEF) • Arrhythmias • Angina • Post-myocardial infarction
★ = Most commonly used / high-yield agents
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
Generations of Beta-Blockers
1st Generation – Nonselective (β1 + β2 Blockade)
Block both β1 and β2 receptors.
• ★ Propranolol • Nadolol • Timolol • Sotalol • Penbutolol • Carteolol
Clinical Notes:
• Avoid in asthma / severe COPD • Sotalol also has Class III antiarrhythmic activity
2nd Generation – Cardioselective (β1 Selective)
Primarily block β1 receptors.
• ★ Metoprolol • ★ Bisoprolol • ★ Atenolol • ★ Esmolol (IV, ultra short-acting) • Nebivolol • Acebutolol • Betaxolol • Celiprolol
Clinical Notes:
• Preferred in reactive airway disease • Selectivity is dose-dependent • Esmolol used in ICU / acute arrhythmias
3rd Generation – Vasodilating Beta-Blockers
Provide additional vasodilation via α1 blockade or nitric oxide release.
Alpha/Beta Blockade:
• ★ Carvedilol • ★ Labetalol
Nitric Oxide–Mediated:
• ★ Nebivolol
Less Common:
Clinical Notes:
• Lower SVR in addition to HR reduction • Carvedilol reduces mortality in HFrEF • Labetalol commonly used in hypertensive emergencies
Beta-Blocker Comparison Table
| Drug | Generation | Beta-1 Selective | Alpha-1 / Vasodilation | Lipophilic vs Hydrophilic | HFrEF Mortality Benefit | Common Uses |
|---|---|---|---|---|---|---|
| ★ Propranolol | 1st | No | No | Lipophilic | No | Migraine, tremor, portal HTN |
| Sotalol | 1st | No | No | Hydrophilic | No | AF, ventricular arrhythmias |
| ★ Metoprolol | 2nd | Yes | No | Lipophilic | Only Succinate | HTN, CAD, AF |
| ★ Bisoprolol | 2nd | Yes | No | Moderate | Yes | HFrEF, HTN |
| ★ Atenolol | 2nd | Yes | No | Hydrophilic | No | HTN (historical) |
| ★ Esmolol | 2nd | Yes | No | Hydrophilic | No | ICU rate control |
| ★ Carvedilol | 3rd | No | Yes (alpha-1) | Lipophilic | Yes | HFrEF, HTN |
| ★ Labetalol | 3rd | No | Yes (alpha-1) | Moderate | No | HTN emergency, pregnancy |
| ★ Nebivolol | 3rd | Yes | NO-mediated | Lipophilic | No | HTN |
Intrinsic Sympathomimetic Activity (ISA)
Partial agonist activity:
• Pindolol • Acebutolol • Penbutolol
Less commonly used in modern practice.
Evidence-Based Heart Failure Agents (Mortality Benefit)
• ★ Carvedilol • ★ Metoprolol Succinate • ★ Bisoprolol
Not all beta-blockers reduce mortality in HFrEF.
Indications by Clinical Context
Hypertension: • Not first-line for uncomplicated HTN • Preferred when CAD, arrhythmia, or HFrEF present
Arrhythmias: • Rate control in atrial fibrillation • SVT suppression
Angina: • Reduce myocardial oxygen demand
Hypertensive Emergency: • ★ Labetalol • ★ Esmolol
Adverse Effects
• Bradycardia • AV block • Hypotension • Fatigue • Depression • Erectile dysfunction • Masked hypoglycemia • Bronchospasm (nonselective agents)
Contraindications
• Severe bradycardia • High-grade AV block (without pacemaker) • Cardiogenic shock • Acute decompensated heart failure
Use caution in:
• Asthma • Severe peripheral vascular disease
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
Related:
→ Hypertension Module → Heart Failure Module → Dysrhythmias Module → Return to Cardiovascular Modules