USMLE

Octreotide

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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

Summary

Octreotide is a long-acting somatostatin analog that acts by inhibiting the secretion of various hormones including vasoactive intestinal peptide or VIP, glucagon, growth hormone, and others. This inhibitory action on hormone production makes octreotide useful in the management of various clinical conditions caused by excess hormones production. Notably, octreotide is used to treat acromegaly and gigantism through its inhibitory effects on growth hormone production. It is also used to treat esophageal varices, by way of blocking glucagon production to indirectly cause splanchnic vasoconstriction. Octreotide is also used to treat secretory diarrhea caused by excess hormones such as in VIPoma or carcinoid syndrome. Lastly, octreotide can lead to the side effect of gallstones due to its inhibition of cholecystokinin production.

Key Points

  • Octreotide
    • Mechanism
      • Somatostatin analog
        • Acts like somatostatin but with a longer half-life
        • Decreases release of various splanchnic vasodilatory hormones (VIP, gastrin, glucagon, CCK, GH)
          • Inhibitory effect on α- and β-islet cells in pancreas
          • Inhibits secretin, cholecystokinin, gastrin, insulin, glucagon, VIP secretion in GI tract
          • Inhibits thyroid stimulating hormone (TSH) production
          • Inhibits action of growth hormone (GH)
    • Indications
      • Esophageal varices
        • Inhibits release of vasodilator hormones such as glucagon, indirectly causing splanchnic vasoconstriction and decreased portal inflow.
      • Secretory diarrhea
        • Inhibits hormone release (e.g. serotonin, VIP) causative of secretory diarrhea
        • Carcinoid Syndrome
          • Carcinoid tumors in the GI secrete a variety of substances including serotonin, which can lead to diarrhea, flushing, and other symptoms
        • VIPoma
          • Pancreatic endocrine tumors characterized by overproduction of VIP, causing secretory diarrhea
      • Acromegaly (overproduction of GH)
      • Gastrinoma
      • Glucagonoma
    • Adverse Effects
      • Increased risk of gallstones (cholelithiasis and cholecystitis)
        • inhibits cholecystokinin, which increases bile stasis
      • GI upset (steatorrhea, nausea, cramps)
        •  Mainly caused by inhibition of other GI hormones