GI Drugs
  1. Ondansetron
  2. Sucralfate
  3. Docusate (Stool Softener)
  4. Bulk Forming Laxatives (Psyllium, Methylcellulose)
  5. Stimulant Laxatives (Senna, Bisacodyl)
  6. Bismuth Subsalicylate
  7. Antidiarrheals (Loperamide, Diphenoxylate-Atropine)
  8. Antacids
  9. Metoclopramide
  10. Misoprostol
  11. Proton Pump Inhibitors (PPIs)
  12. Orlistat
  13. Octreotide


Ondansetron is a medication used to treat nausea and vomiting. As a serotonin receptor blocker, it can cause an abnormality in serotonin signaling known as serotonin syndrome, which is a life-threatening medical emergency that presents with unstable vitals, muscle rigidity, as well as agitation and restlessness.

Key Points

  • Ondansetron (Zofran)
    • Mechanism
      • Serotonin (5-HT3) antagonist
        • Blocks the serotonin receptors in the chemoreceptor trigger zone (CZ)
        • Blocks the afferent vagal neurons in the upper GI tract
    • Clinical Uses
      • Nausea and vomiting
        • Chemotherapy
        • Postoperative recovery
          • Treat n/v side effects of anesthesia and narcotics
          • Prevent dehiscence and evisceration of wounds associated with abdominal strain from vomiting
    • Side Effects and Adverse Reactions
      • Serotonin Syndrome
        • By blocking the serotonin receptors, more serotonin is in the synapses and can lead to serotonin syndrome
        • Muscle rigidity, restlessness, agitation, tachycardia
      • Headache
        • Most common side effect
      • Prolonged QT interval
        • Can lead to torsade de Pointes
        • Monitor heart rhythm in patients with present cardiac disorders
        • If giving IV, give slowly over 2-5 minutes
      • Hypotension
      • Dizziness