Beta Blockers

Summary

Beta blockers are a class of medications that commonly end in a -lol ending, including propranolol, atenolol, carvedilol, and metoprolol.  These drugs are commonly used to treat hypertension and chronic heart failure. Beta-blockers work by blocking beta-adrenergic receptors on the heart, preventing catecholamines like epinephrine and norepinephrine from inducing a "fight or flight response". This reduces contractility of the heart and slows down the heart rate. These drugs can cause bradycardia, so make sure to check your patient’s pulse before administration. Other important adverse effects to watch out for with beta-blockers include bronchospasm and the masking of hypoglycemia in diabetics.

Key Points

• Beta Blockers
  • Key Drugs (-lol endings)
    • Atenolol
    • Metoprolol
    • Carvedilol
    • Propranolol
  • Mechanism
    • Block beta-adrenergic receptors so that catecholamines (e.g. norepinephrine and epinephrine) cannot bind to them to elicit a sympathetic (fight-or-flight) nervous response
      • Reduce heart rate and contractility (cardiac output)
    • Selective beta blockers
      • Selective to only beta-1 receptors
        • Beta-1 receptors are located mainly in the heart and kidneys
        • Includes atenolol and metoprolol
    • Non-selective beta blockers
      • Block both beta-1 and beta-2 receptors
        • Beta-2 receptors are located in the lungs, GI tract, vascular smooth muscle, and skeletal muscle
        • These drugs have more side effects
        • Includes carvedilol and propranolol
  • Clinical Use
    • Hypertension
      • Due to decreased cardiac output
    • Chronic heart failure
      • Reduced contractility and heart rate reduce work of heart, improving long-term survival
    • Stable angina
      • May reduce symptoms and work of heart, but does not improve survival
    • Dysrhythmias
      • Beta-blockers are used as a Class II antiarrhythmic
  • Side Effects and Adverse Reactions
    • Bradycardia
      • Do not give if pulse <60
      • Due to beta-blocker suppression of activity at the SA/AV node]
      • May also cause varying degree of Heart (AV) Block
        • Inhibition of sympathetic signalling at AV node can lead to heart block and cardiac arrest
    • Bronchospasm/Wheezing
      • Contraindicated in patients with asthma and COPD
      • Occurs as a result of non-selective beta-blockers blocking the beta- 2 receptors in the lungs, causing bronchoconstriction
    • Masks hypoglycemic symptoms
      • Closely monitor blood glucose levels in diabetic patients
      • Patient will not experience tachycardia due to the effects of the beta-blocker
    • Hypotension
      • Common side effect of all antihypertensive drugs
    • Rebound hypertension and angina
      • Do not stop abruptly; taper over 2-3 weeks
    • Other non-selective side effects include peripheral vasoconstriction, hyperglycemia, and decreased intraocular pressure
      • Avoid in patients with peripheral vascular disease
      • May cause cold extremities and erectile dysfunction