USMLE

Antidiarrheals (Loperamide, Diphenoxylate-Atropine)

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

Summary

Antidiarrheals, including the drugs loperamide and diphenoxylate-atropine, are used to reduce frequency and liquidity of stool.

Key Points

  • Antidiarrheals
    • Key Drugs
      • Loperamide (Imodium)
        • Synthetic analog of the opioid meperidine
      • Diphenoxylate-atropine (Lomotil)
        • An opiate combination drug with anticholinergic properties
    • Mechanism
      • Slows intestinal motility by binding to the opiate receptor in the wall of the GI tract
      • Increased absorption of fluids and electrolytes in the intestinal tract
    • Clinical Use
      • Treats Diarrhea
        • Provide symptomatic relief (decrease in frequency and liquidity of stool)
        • Does not treat the underlying cause (e.g. bacterial infection would also need antibiotics)
    • Side Effects and Adverse Reactions
      • Central Nervous System Effects (Diphenoxylate)
        • If given in high doses; generally not seen when given in a low dose
        • Euphoria, CNS depression, dizziness, fatigue
        • The atropine addition in diphenoxylate-atropine discourages abuse because patients will receive anticholinergic side effects in addition to opioid side effects