Norepinephrine

Summary

Norepinephrine is an adrenergic agonist. This means that it stimulates the sympathetic nervous system. In other words, it activates the fight or flight response.

Norepinephrine is most commonly used to treat hypotension and shock.

It does this by activating the beta-1 receptors, which causes positive inotropy and increases cardiac output. It also activates alpha-1 receptors, which causes vasoconstriction and increases the blood pressure. Norepinephrine also activates alpha-2 receptors.

Norepinephrine can cause hypertension as a side effect, and the blood pressure must be closely monitored during treatment. Extravasation of the drug can cause tissue necrosis. If this occurs, you can expect to treat extravasation with phentolamine. Norepinephrine can also cause arrhythmias.

Key Points

• Norepinephrine
  • Mechanism
    • Adrenergic Agonist
      • Activates Alpha 1 Receptors
        • Vasoconstriction
          • Increases Blood Pressure
          • Alpha-1 receptors can be found on vascular smooth muscle cells
      • Activates Beta 1 Receptors
        • Increases Myocardial Contractility (Positive Inotrope)
        • Increases Cardiac Output
        • Increases heart rate
    • Stimulates Sympathetic Nervous System
      • “Fight or flight”
      • Also called a sympathomimetic
  • Clinical Use
    • Hypotension
      • Through the activation of alpha-1 receptors, norepinephrine increases blood pressure to treat hypotension
    • Shock
      • Shock happens when the body isn’t getting enough blood flow
      • Norepinephrine increases the blood flow through the body through activation of alpha-1 and beta-1 receptors
  • Side Effects
    • Arrhythmias
    • Hypertension
    • Tissue necrosis around IV site
      • Extravasation (leakage from the vein into surrounding tissue) of norepinephrine can cause death of the surrounding tissue due to its vasoconstrictive effects
      • If this occurs, treat with phentolamine