Which of the following solutions is an example of a hyperosmotic preparation?

A hyperosmotic preparation is characterized by its ability to draw water into the intestines or a specific area, thereby increasing osmolarity and promoting fluid shifts. Magnesium citrate fits this definition, as it has a high osmotic potential due to its ionic composition. This hyperosmotic solution can effectively attract water into the gastrointestinal tract, which is why it is commonly used as a laxative to relieve constipation or to prepare the bowel for procedures.

In contrast, polyethylene glycol is an isotonic solution often used to clean out the intestines, rather than being hyperosmotic. Sodium bicarbonate does not exert a hyperosmotic effect but rather functions to neutralize acid. Dextrose solution, although a sugar solution, is also not hyperosmotic in the same sense, as it does not significantly draw water into the intestines compared to magnesium citrate. The action of magnesium citrate as a hyperosmotic agent is key to its use in clinical practice.