Which drug is used to treat diarrhea and is a Class V controlled substance?

• A. Loperamide
• B. Morphine
• C. Diphenoxylate
• D. Hydrocodone

Answer: (C)

Diphenoxylate is an opioid that acts in the gut to slow intestinal motility, giving more time for water absorption and producing firmer stools, which helps treat diarrhea. It’s often given with atropine to deter abuse; the atropine adds a counteractive effect at higher doses, making misuse less appealing. This combination is why it’s classified as a Schedule V (Class V) controlled substance.

Other options either aren’t controlled substances or aren’t the standard diarrhea treatment: loperamide is also used for diarrhea but is not a controlled substance, while morphine and hydrocodone are stronger opioids used for pain, with higher abuse potential and not used as first-line antidiarrheal therapies.