Antidiarrheal medications primarily function by:

Antidiarrheal medications primarily function by decreasing intestinal motility. When diarrhea occurs, it is often due to increased peristalsis in the gastrointestinal tract, which accelerates the transit time of stool through the intestines. This rapid movement can prevent adequate absorption of nutrients and fluids, leading to the characteristic symptoms of diarrhea.

By decreasing intestinal motility, antidiarrheal medications allow more time for the intestines to absorb water and electrolytes from the stool, thereby leading to firmer stools and reducing the frequency of bowel movements. Medications such as loperamide and diphenoxylate act specifically by binding to opioid receptors in the gut, which slows down the movement of the intestines.

Given this mechanism, the reduction of motility not only helps in managing the symptoms of diarrhea but also aids in restoring the normal function of the intestinal tract. Therefore, the primary function of antidiarrheal medications is to decrease intestinal motility to alleviate diarrhea and its accompanying symptoms.