Beta-1 Selective Blockers (Atenolol, Esmolol, Metoprolol)

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Summary

Selective Beta-1 blockers are a class of drugs including esmolol, atenolol, and metoprolol. These drugs block signaling from beta-1 receptors, which works at the heart to reduce heart rate and contractility. The net result of this action is reduced cardiac output and reduced workload on the heart. Beta blockers are used for a variety of indications due to this mechanism, including treatment of hypertension, angina, or heart failure. A notable side effect of metoprolol is dyslipidemia, which is relatively unique on top of the general cardiovascular depression caused by beta-1 blockade.

Key Points

  • Beta-1 Selective Blockers
    • Drug Names
      • Atenolol
      • Esmolol
      • Metoprolol
      • Acebutolol
      • Betaxolol
      • Bisoprolol
    • Mechanism
      • Selective Beta-1 Blockade
        • Decreased HR (Chronotropy and Dromotropy) and Stroke Volume (Inotropy) → Decreased Cardiac Output
        • Reduces renin release
    • Clinical use
      • Decreases myocardial oxygen demand
        • Angina Pectoris
        • Myocardial Infarction
      • Decreased Contractility
        • HCM
          • Decreased contractility decreases the Left Ventricular Outflow Obstruction
      • Decreased AV Nodal Conduction
        • Supraventricular Tachycardia
          • Decreased Dromotropy → Ventricle receives signals more slowly → Rate Control
      • Decreased Renin Release
        • Heart Failure
          • Decreased Renin → Less RAAS-mediated fluid retention → Less Congestion in Body
    • Adverse Effects
      • Erectile Dysfunction
      • Cardiovascular (Bradycardia, AV Block, CHF)
        • AV Block caused by decreased dromotropy, will present with elongated PR Interval (will be discussed alongside Decreased AV Nodal Conduction, does not need separate symbol)
      • CNS (seizures, sleep alterations)
      • Dyslipidemia (Metoprolol)
      • Asthma/COPD Exacerbation
        • Asthma/COPD Exacerbation and Hypoglycemia should not be as severe as nonselectives because lack of Beta 2 antagonism
      • Hypoglycemia (Mictlan)