Difenoksylan

Difenoksylan is a synthetic opioid that is primarily used as an antidiarrheal medication. It acts by slowing down the motility of the intestines, which reduces the frequency of bowel movements. Difenoksylan is often combined with atropine sulfate in a single medication to deter abuse, as atropine can cause unpleasant side effects like blurred vision, dry mouth, and rapid heart rate if taken in excessive amounts. This combination is available by prescription only.

The mechanism of action of difenoksylan involves binding to opioid receptors in the myenteric plexus of the large intestine. This interaction inhibits the release of acetylcholine and prostaglandins, which are neurotransmitters and signaling molecules that stimulate intestinal contractions and secretions. By reducing these effects, difenoksylan effectively decreases peristalsis and slows the transit of intestinal contents, allowing for more water absorption and firmer stools.

While effective for treating diarrhea, difenoksylan carries a risk of dependence and abuse due to its opioid properties. In therapeutic doses, central nervous system effects are minimal, but overdose can lead to respiratory depression, sedation, and coma. Due to these risks, it is classified as a Schedule V controlled substance in the United States. It is not recommended for use in children under a certain age due to the increased risk of severe adverse effects.