Cardiovascular

Beta Blockers

Cardiovascular

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Examples

metoprololatenololpropranolol

Prefix / Suffix: -lol

Physiology

Beta receptors respond to sympathetic stimulation. β1 receptors (heart) increase heart rate, contractility, and conduction. β2 receptors (lungs, vessels) cause bronchodilation and vasodilation. Beta blockers reduce this stimulation, affecting the heart and sometimes the lungs depending on selectivity.

Mechanism of Action

They block beta-adrenergic receptors. Selective (β1 blockers) mainly act on the heart → ↓ heart rate, ↓ contractility. Non-selective (β1 + β2 blockers) act on heart and lungs → ↓ heart activity + bronchoconstriction.

Indications

  • Hypertension
  • Angina
  • Heart failure
  • Myocardial infarction
  • Arrhythmias

Side Effects / Adverse Effects

  • Bradycardia (due to reduced heart rate)
  • Hypotension (due to reduced cardiac output)
  • Fatigue (due to decreased cardiac output)
  • Bronchospasm (non-selective blockers affect β2 receptors in lungs)
  • Masking hypoglycemia (blocks adrenergic warning signs like tachycardia)

Contraindications

  • Severe bradycardia
  • Heart block
  • Cardiogenic shock
  • Asthma (especially non-selective beta blockers)

Nursing Considerations

  • Check heart rate before giving (hold if HR < 60 bpm due to risk of severe bradycardia)
  • Monitor blood pressure (risk of hypotension)
  • Do not stop abruptly (can cause rebound hypertension and tachycardia)
  • Prefer β1-selective drugs in asthma patients (reduces risk of bronchospasm compared to non-selective)
  • Monitor respiratory status (non-selective drugs can cause bronchoconstriction)
  • Monitor blood glucose in diabetics (can mask hypoglycemia symptoms)
  • Assess for fatigue and dizziness (due to reduced cardiac output)

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