Gastrointestinal Pharm
  1. H2 Blockers (Cimetidine, Ranitidine, Famotidine)
  2. Proton Pump Inhibitors (PPIs)
  3. Misoprostol
  4. Orlistat
  5. Antacids
  6. Bismuth & Sucralfate
  7. Octreotide
  8. Diphenoxylate vs. Loperamide
  9. Ondansetron
  10. Metoclopramide
  11. Bulk-forming Laxatives
  12. Senna
  13. Docusate
  14. Aprepitant


Ondansetron is a 5-HT3 Serotonin receptor antagonist, used to treat nausea and vomiting. As a drug modulating serotonin, serotonin syndrome is a potential adverse effect. Another important side effect is QT prolongation, which can result in Torsades de Pointes.

Key Points

  • Ondansetron
    • Mechanism
      • Serotonin (5-HT3) antagonist
        • Acts in area postrema of medulla (vomiting centers)
          • Central-acting antiemetic
        • Also acts at peripheral and enteric nerves
          • Decrease vagal stimulation to GI tract
    • Clinical Use
      • Antiemetic
        • Especially in setting of GI-injury (e.g. postoperative, infection) or chemotherapy
    • Adverse Effects
      • Serotonin syndrome
        • Any drug that modulates serotonin signaling may lead to serotonin syndrome
      • QT interval prolongation
        • Risk for Torsades de Pointes
      • Headache
      • Constipation