A 40-year-old woman comes to the office with a 4-week history of diarrhea accompanied by occasional abdominal bloating. She has noticed that her stools contain mucus but has not seen any blood. The patient also has intermittent mild heartburn. She has no fevers, chills, or weight loss. The patient has also noticed an unpleasant taste with dairy products and now avoids them. Past medical history is significant for chronic allergic rhinitis. Current medications include only a multivitamin supplement. Vital signs and physical examination are normal. After a basic evaluation, the patient is started on a trial of diphenoxylate therapy. Which of the following is the primary target of this drug?

Question

A 40-year-old woman comes to the office with a 4-week history of diarrhea accompanied by occasional abdominal bloating.  She has noticed that her stools contain mucus but has not seen any blood.  The patient also has intermittent mild heartburn.  She has no fevers, chills, or weight loss.  The patient has also noticed an unpleasant taste with dairy products and now avoids them.  Past medical history is significant for chronic allergic rhinitis.  Current medications include only a multivitamin supplement.  Vital signs and physical examination are normal.  After a basic evaluation, the patient is started on a trial of diphenoxylate therapy.  Which of the following is the primary target of this drug?

Quizplus · Accepted Answer

This patient has uncomplicated diarrhea with benign findings on initial examination and evaluation. Common causes include irritable bowel syndrome and functional diarrhea. In such cases, empiric symptomatic therapy is often considered prior to more complex testing. Diphenoxylate is an opioid anti-diarrheal agent structurally related to meperidine. It binds to mu opiate receptors in the gastrointestinal tract and slows motility. Low doses relieve diarrhea without other significant opiate effects. However, higher doses can produce morphine-like euphoria and physical dependence. To discourage abuse, diphenoxylate is combined with atropine, which produces adverse symptoms (dry mouth, blurry vision, nausea) if taken in high doses. Loperamide is another low-potency opioid agonist used in the symptomatic treatment of diarrhea. Common side effects of these drugs include rebound constipation and mild sedation. They should not be used in diarrhea due to toxin-producing or invasive organisms (eg, Shigella, Salmonella) or Clostridium difficile infections. (Choices A and B) Substances that are poorly digested or absorbed can retain fluid in the intestinal lumen and cause diarrhea. Lactase enzyme supplements are used in patients with lactase deficiency who have diarrhea due to undigested dietary lactose. Patients with exocrine pancreatic deficiency often have diarrhea due to undigested fats; pancreatic enzyme supplements are useful in these individuals. (Choice C) Ulcerative colitis and Crohn disease are inflammatory bowel diseases that commonly present with diarrhea. Inflammation of the gut causes mucous, proteinaceous, and bloody discharge that leads to diarrhea. Treatment involves anti-inflammatory drugs, corticosteroids, and other immunosuppressive agents. This patient lacks inflammatory features. (Choice E) Secretory diarrhea can be due to many different substances (eg, vasoactive intestinal peptide, bacterial toxins) that increase secretions. Agents that target secretory diarrhea include bismuth subsalicylate, octreotide, and possibly some probiotic preparations. Educational objective: Diphenoxylate is an opioid antidiarrheal drug that binds mu opiate receptors in the gut to slow motility. Overuse can lead to euphoria and physical dependence. To discourage abuse, diphenoxylate is combined with atropine, which induces adverse effects if taken in high doses.

A 40-Year-Old Woman Comes to the Office with a 4-Week