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cardio:beta_blockers:start [2026/02/12 23:26] – andrew2393cnscardio:beta_blockers:start [2026/02/12 23:47] (current) – [Mechanism of Action] andrew2393cns
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 Beta-blockers antagonize beta-adrenergic receptors and reduce sympathetic stimulation of the cardiovascular system. Beta-blockers antagonize beta-adrenergic receptors and reduce sympathetic stimulation of the cardiovascular system.
  
-Primary Effects:+Primary Physiologic Effects:
  
 • ↓ Heart rate   • ↓ Heart rate  
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 • ↓ Blood pressure   • ↓ Blood pressure  
  
-They are used in:+Used in:
  
 • [[cardio:hypertension:start|Hypertension]]   • [[cardio:hypertension:start|Hypertension]]  
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 • [[cardio:angina:start|Angina]]   • [[cardio:angina:start|Angina]]  
 • Post-myocardial infarction   • Post-myocardial infarction  
 +
 +★ = Most commonly used / high-yield agents
  
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 ===== Mechanism of Action ===== ===== Mechanism of Action =====
  
-Beta receptors:+β1 receptors: 
 +• Heart (↑ HR, ↑ contractility) 
 +• Kidney (↑ renin) 
 + 
 +β2 receptors: 
 +• Bronchi (bronchodilation) 
 +• Vascular smooth muscle
  
-• β1 – Heart & kidney (↑ HR, ↑ contractility, ↑ renin)   +Beta-blockers:
-• β2 – Bronchi & vascular smooth muscle (bronchodilation)  +
  
-Beta-blockers reduce:+• Block β1 (cardiac effects) 
 +• Some also block β2 
 +• Some provide additional vasodilation (α1 or NO-mediated)
  
-• Cardiac output   +Reference: [[autonomics:start|Autonomic Receptors]]
-• Myocardial oxygen demand   +
-• RAAS activation  +
  
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 Block both β1 and β2 receptors. Block both β1 and β2 receptors.
  
-• [[cardio:beta_blockers:propranolol|Propranolol]]   +• ★ [[cardio:beta_blockers:propranolol|Propranolol]] 
-• [[cardio:beta_blockers:nadolol|Nadolol]]   +• [[cardio:beta_blockers:nadolol|Nadolol]] 
-• [[cardio:beta_blockers:timolol|Timolol]]  +• [[cardio:beta_blockers:timolol|Timolol]] 
 +• [[cardio:beta_blockers:sotalol|Sotalol]] 
 +• [[cardio:beta_blockers:penbutolol|Penbutolol]] 
 +• [[cardio:beta_blockers:carteolol|Carteolol]]
  
-Characteristics:+Clinical Notes:
  
-• Higher risk of bronchospasm   +• Avoid in asthma / severe COPD   
-• Avoid in asthma or severe COPD  +• Sotalol also has Class III antiarrhythmic activity  
  
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 Primarily block β1 receptors. Primarily block β1 receptors.
  
-• [[cardio:beta_blockers:metoprolol|Metoprolol]] +• ★ [[cardio:beta_blockers:metoprolol|Metoprolol]] 
-• [[cardio:beta_blockers:atenolol|Atenolol]] +• ★ [[cardio:beta_blockers:bisoprolol|Bisoprolol]] 
-• [[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:nebivolol|Nebivolol]]
 • [[cardio:beta_blockers:acebutolol|Acebutolol]] • [[cardio:beta_blockers:acebutolol|Acebutolol]]
 +• [[cardio:beta_blockers:betaxolol|Betaxolol]]
 +• [[cardio:beta_blockers:celiprolol|Celiprolol]]
  
-Preferred in:+Clinical Notes:
  
-• Reactive airway disease   +• Preferred in reactive airway disease   
-• Diabetes   +• Selectivity is dose-dependent   
- +• Esmolol used in ICU / acute arrhythmias  
-Note: +
-Selectivity is dose-dependent (lost at higher doses).+
  
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 ==== 3rd Generation – Vasodilating Beta-Blockers ==== ==== 3rd Generation – Vasodilating Beta-Blockers ====
  
-Provide additional vasodilation via: +Provide additional vasodilation via α1 blockade or nitric oxide release.
- +
-• α1 blockade   +
-• Nitric oxide release  +
  
 Alpha/Beta Blockade: Alpha/Beta Blockade:
  
-• [[cardio:beta_blockers:labetalol|Labetalol]] +• ★ [[cardio:beta_blockers:carvedilol|Carvedilol]] 
-• [[cardio:beta_blockers:carvedilol|Carvedilol]]+• ★ [[cardio:beta_blockers:labetalol|Labetalol]]
  
-Nitric Oxide–Mediated Vasodilation:+Nitric Oxide–Mediated:
  
-• [[cardio:beta_blockers:nebivolol|Nebivolol]]+• ★ [[cardio:beta_blockers:nebivolol|Nebivolol]]
  
-Effects:+Less Common:
  
-• ↓ Heart rate   +• [[cardio:beta_blockers:bucindolol|Bucindolol]]
-• ↓ Contractility   +
-• ↓ SVR  +
  
-Often better tolerated metabolically.+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 ^
 +|[[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) ===== ===== Intrinsic Sympathomimetic Activity (ISA) =====
  
-Some beta-blockers partially stimulate β receptors while blocking them.+Partial agonist activity:
  
 • [[cardio:beta_blockers:pindolol|Pindolol]] • [[cardio:beta_blockers:pindolol|Pindolol]]
 • [[cardio:beta_blockers:acebutolol|Acebutolol]] • [[cardio:beta_blockers:acebutolol|Acebutolol]]
 +• [[cardio:beta_blockers:penbutolol|Penbutolol]]
  
 Less commonly used in modern practice. Less commonly used in modern practice.
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 -------------------------------------------------------------------- --------------------------------------------------------------------
  
-===== Indications =====+===== Evidence-Based Heart Failure Agents (Mortality Benefit) =====
  
-==== Heart Failure (HFrEF) – Mortality Reduction ====+• ★ [[cardio:beta_blockers:carvedilol|Carvedilol]] 
 +• ★ [[cardio:beta_blockers:metoprolol|Metoprolol Succinate]] 
 +• ★ [[cardio:beta_blockers:bisoprolol|Bisoprolol]]
  
-Evidence-based agents:+→ [[cardio:heart_failure:start|Heart Failure Module]]
  
-• [[cardio:beta_blockers:carvedilol|Carvedilol]] +Not all beta-blockers reduce mortality in HFrEF.
-• [[cardio:beta_blockers:metoprolol_succinate|Metoprolol Succinate]] +
-• [[cardio:beta_blockers:bisoprolol|Bisoprolol]]+
  
-→ [[cardio:heart_failure:start|Heart Failure Module]]+--------------------------------------------------------------------
  
-----+===== Indications by Clinical Context =====
  
-==== Hypertension ==== +Hypertension: 
- +• Not first-line for uncomplicated HTN   
-• Not first-line in uncomplicated HTN   +• Preferred when CAD, arrhythmia, or HFrEF present  
-• Preferred in CAD, arrhythmia, or HFrEF  +
  
 → [[cardio:hypertension:start|Hypertension Module]] → [[cardio:hypertension:start|Hypertension Module]]
  
----- +Arrhythmias:
- +
-==== Arrhythmias ==== +
 • Rate control in atrial fibrillation   • Rate control in atrial fibrillation  
-• Suppress supraventricular tachycardia  +• SVT suppression  
  
 → [[cardio:arrhythmias:start|Dysrhythmias Module]] → [[cardio:arrhythmias:start|Dysrhythmias Module]]
  
----- +Angina:
- +
-==== Angina ==== +
 • Reduce myocardial oxygen demand   • Reduce myocardial oxygen demand  
  
 → [[cardio:angina:start|Anti-Anginal Module]] → [[cardio:angina:start|Anti-Anginal Module]]
 +
 +Hypertensive Emergency:
 +• ★ [[cardio:beta_blockers:labetalol|Labetalol]]
 +• ★ [[cardio:beta_blockers:esmolol|Esmolol]]
  
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 • Depression   • Depression  
 • Erectile dysfunction   • Erectile dysfunction  
-• Mask hypoglycemia   +• Masked hypoglycemia   
-• Bronchospasm (1st generation agents)+• Bronchospasm (nonselective agents)
  
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 ✔ Only certain agents reduce mortality in HFrEF   ✔ Only certain agents reduce mortality in HFrEF  
-✔ 2nd generation agents are β1 selective   + 
-✔ 3rd generation agents provide vasodilation  +✔ 1st gen = nonselective   
 + 
 +✔ 2nd gen = β1 selective   
 + 
 +✔ 3rd gen = vasodilating   
 ✔ Avoid abrupt discontinuation (rebound tachycardia)   ✔ Avoid abrupt discontinuation (rebound tachycardia)  
 +
 ✔ Not first-line for uncomplicated hypertension   ✔ Not first-line for uncomplicated hypertension  
  
cardio/beta_blockers/start.1770938798.txt.gz · Last modified: by andrew2393cns