CH 84 Antidiarrheals

Question 1

Drug: Loperamide (Imodium)

Answer 1

Class: Opioid antidiarrheal
MOA: Slows intestinal motility via gut opioid receptors.
Note: Low CNS penetration; very effective with minimal abuse potential.

Question 2

Drug: diphenoxylate + atropine (Lomotil)

Answer 2

Class:
* Diphenoxylate: Opioid antidiarrheal
* Atropine: Anticholinergic (added to discourage abuse)

MOA:
Diphenoxylate:
* Structurally related to meperidine (an opioid)
* Slows GI motility by activating mu-opioid receptors in the intestines
* Increases transit time and absorption of water/electrolytes

Atropine (low dose):
* Added not for therapeutic effect, but to produce unpleasant side effects (e.g., dry mouth, tachycardia) if taken in high doses
* Discourages misuse/abuse of diphenoxylate for euphoria

Schedule V drug

Question 3

Management of Traveler’s Diarrhea

Answer 3

Cause: Often bacterial (e.g., E. coli), sometimes viral or parasitic

Management:
Mild cases: Hydration and dietary rest

Moderate to severe:
* ciprofloxacin (Cipro)
* norfloxacin (Noroxin)
* azithromycin (Zithromax) - preferred for children & pregnant women
* rifaximin (Xifaxan)

Question 4

Management of Clostridium Difficile

Answer 4

Cause: Overgrowth of C. difficile after antibiotic use

Management:
* Stop the causative antibiotic, if possible
* First-line treatment:
– Vancomycin - oral
– Fidaxomicin - oral
* Alternative (non-severe cases):
– metronidazole (Flagyl) - oral

Avoid antimotility agents (e.g., loperamide) due to risk of toxic megacolon