Final answer:
Docusate sodium acts as a stool softener by lowering the surface tension of the stool, allowing water and fats to lubricate it for easier passage. It does not significantly increase bulk formation or motility, unlike nondigestible carbohydrates like insoluble fiber that promote regularity.
Step-by-step explanation:
The mechanism of action (MOA) of docusate sodium is that it acts as a stool softener, which falls under the category of surfactant laxatives. Primarily, it functions by lowering the surface tension of the stool, which allows water and fats to penetrate and lubricate the material. This process softens the stool, making it easier to pass, but it does not significantly affect bulk formation or motility. In contrast, insoluble fiber, which is a nondigestible carbohydrate, does not dissolve in water and provides bulk, which can stimulate peristalsis in the digestive tract to promote regularity. Insoluble fiber sources include whole wheat, wheat bran, beans, and potatoes. This is distinct from docusate sodium's action, which specifically involves easing the passage of stool through the addition of water and lipids.