Which mechanism can cause diarrhea in patients on enteral nutrition due to drugs?

• A. Hyperosmolarity (such as magnesium or sorbitol in formulas)
• B. Direct laxative effect (such as kayexalate)
• C. Antibiotics (which may cause diarrhea without C. difficile overgrowth)
• D. All of the above

Answer: (D)

Drug-related diarrhea in patients receiving enteral nutrition can arise from several mechanisms, any of which may contribute when a patient is exposed to osmotic agents, stimulant effects, or antibiotics.

Hyperosmolarity occurs when the intestinal lumen is loaded with osmoles from the formula or additives, such as magnesium-containing components or sorbitol. This osmotic load draws water into the gut, increasing stool water content and accelerating transit, which leads to diarrhea.

A direct laxative effect is another route. Some medications or resin treatments used with enteral nutrition can stimulate gut motility or soften stools independently of osmotic load—for example, kayexalate can have a laxative-type effect that results in diarrhea.

Antibiotics disrupt the normal gut microbiota, which can cause diarrhea by altering microbial balance and function. This can occur with or without overgrowth of Clostridioides difficile; antibiotic-associated diarrhea is a recognized mechanism in EN patients.

Because all three pathways are possible, diarrhea in patients on enteral nutrition can result from any of these drug-related mechanisms, and multiple mechanisms may coexist.