Review Question - QID 101064

The patient described in the question has a lactase deficiency (aka lactose intolerance) in which undigested lactose acts as an osmotic agent to pull water into the lumen, resulting in osmotic diarrhea. Magnesium hydroxide is an osmotic laxative.

Osmotic diarrhea presents with the loss of large volumes of diarrhea without inflammation of the enterocytes. It is caused by the presence of osmotically active substance drawing hypotonic solution into the lumen, most commonly seen with giardiasis, laxative use (e.g. Mg-containing products), and disaccharidase deficiency (e.g. lactase deficiency).

Incorrect Answers:
Answer 1: Omeprazole is a proton pump inhibitor (PPI) and plays no role in the pathogenesis of osmotic diarrhea.
Answer 2: Bismuth provides physical protection to an ulcer base as well as other functions. It plays no role in the pathogenesis of osmotic diarrhea.
Answer 3: Ranitidine is an H2 blocker and plays no role in the pathogenesis of osmotic diarrhea.
Answer 4: Octreotide is a somatostatin analog and plays no role in the pathogenesis of osmotic diarrhea.