Medicine & USMLE


GI Drugs
  1. Ondansetron
  2. Sucralfate
  3. Docusate (Stool Softener)
  4. Bulk Forming Laxatives (Psyllium, Methylcellulose)
  5. Osmotic Laxatives (Lactulose, PEG)
  6. Stimulant Laxatives (Senna, Bisacodyl)
  7. Antidiarrheals (Loperamide, Diphenoxylate-Atropine)
  8. Bismuth Subsalicylate
  9. Antacids
  10. Proton Pump Inhibitors (PPIs)
  11. H2 Blockers
  12. Metoclopramide
  13. Misoprostol
  14. Orlistat
  15. 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