Adenosine

Summary

Adenosine is an antiarrhythmic drug that is commonly used to treat SVT. It works by increasing potassium efflux out of cells, causing hyperpolarization, and blocking calcium currents into the cell. This causes slowed conduction at the AV node. Adenosine is very short acting, with a duration of action lasting 15 seconds or less. Notably, the actions of adenosine can be blunted by theophylline or caffeine. Side effects of adenosine include a sense of impending doom, chest pain, bronchospasm, hypotension, and flushing.

Key Points

• Adenosine
  • Mechanism
    • Decreases AV node conduction
      • Uses 2 distinct mechanisms to suppress nodal conduction
      • ↑ Potassium efflux out of cells
        • Binds to adenosine receptors on the heart, activating a Gi-mediated pathway that leads to opening of potassium channels
        • Hyperpolarizes the cell
          • Potassium efflux causes hyperpolarization of nodal cells which suppresses conduction
      • Decreased inward calcium current
        • Inhibition of L-type calcium channels prevents influx of calcium in phase 0 of nodal action potential
    • Very short acting (~15 seconds)
      • Short duration of action is ideal for terminating some types of arrhythmias with minimal long-term side effects
    • Effects blunted by theophylline and caffeine
      • Theophylline and Caffeine are adenosine receptor antagonists, which block the drug from binding to its receptors on the heart
  • Clinical Use
    • Diagnoses/Treats certain forms of SVT
      • Most commonly used to terminate paroxysmal SVT (pSVT)
      • Diagnosis refers to responsiveness to treatment with adenosine; arrhythmias that can be terminated by adenosine belong to a certain class of SVT.
  • Side Effects
    • Sense of Impending Doom
      • This is a salient feature of this drug; patients often report that they feel like something really bad is about to happen during the transient period of the drug’s effects
    • Chest Pain
      • This is largely thought to be caused by bronchospasm below, although other factors are involved
    • Bronchospasm
    • Flushing
    • Hypotension
      • This is usually transient and results from reduced heart rate and AV conduction