Nitroprusside

Summary

Nitroprusside is a medication used primarily to treat hypertensive emergencies by lowering blood pressure. Nitroprusside works in the body to increase cyclic GMP through the release of nitric oxide in blood vessels, which eventually causes vasodilation. Notably, nitroprusside causes nearly equal dilation of both arteries and veins. The drug is short acting with effects on the body usually lasting less than 10 minutes. At high doses, nitroprusside can cause the side effect of cyanide toxicity.

Key Points

• Nitroprusside
  • Clinical Use
    • Treats Hypertensive emergency
      • Used due to its quick onset and short duration of action
    • Treats Hypertension
    • Acute decompensated heart failure
      • Helps to reduce afterload (and preload), reducing the work on the heart
  • Mechanism
    • Potent vasodilator
      • Direct release of NO → Increases cGMP
        • Does not depend on intracellular metabolism into NO (I like to think that this is why it affects arteries equally)
        • relaxes vascular smooth muscle
      • Dilates arteries = veins (balanced)
        • Contrast vs. nitrates, which primarily target veins
        • Nitroprusside targets both preload and afterload
    • Short Duration of Action <10 Min
  • Side Effects
    • Cyanide toxicity
      • Metabolized into cyanide and thiocyanate, which limits dosing
    • Hypotension (obvious)
    • May cause increased intracranial pressure
      • Via vasodilation of cerebral arteries