Combined Alpha-Beta Blockers (Carvedilol, Labetalol)

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Summary

Carvedilol and labetalol are nonselective alpha and beta blockers that block alpha 1, beta 1 and beta 2 receptors. All together, these effects reduce cardiac output and reduce systemic blood pressure by way of vasodilation. Carvedilol and labetalol are often used for the treatment of hypertension and heart failure, and they may also be used to combat the cardiovascular effects of cocaine use.

Key Points

  • Nonselective Alpha and Beta Blockers
    • Drug Names
      • Carvedilol
      • Labetalol
    • Mechanism of Action
      • Antagonism of Alpha and Beta Receptors
        • Alpha 1 Antagonist
          • Alpha 1 Blockade → Decreased vasoconstriction → Decreased TPR → Decreased BP
        • Beta 1 Antagonist
          • Decreased HR (Chronotropy and Dromotropy) and Stroke Volume (Inotropy) → Decreased Cardiac Output
        • Beta 2 Antagonist
          • Bronchoconstriction, Vasoconstriction
    • Clinical Use
      • Carvedilol: Heart Failure, Variceal bleeding, Class II Antiarrhythmic
      • Labetalol: Hypertension in Pregnancy, Hypertensive emergency, Cocaine Toxicity, Heart Failure
    • Adverse Effects
      • Erectile Dysfunction, Cardiovascular (Bradycardia, AV Block, CHF), CNS (seizures, sleep alterations), Asthma/COPD Exacerbation, Hypoglycemia
        • AV Block caused by decreased dromotropy, will present with elongated PR Interval
        • Asthma/COPD exacerbation caused by bronchoconstriction
        • Hypoglycemia caused by beta 2 antagonism, leading to decreased hepatic glycogenolysis/gluconeogenesis and also masking of autonomic symptoms of hypoglycemia