Antidiarrheals: Nursing pharmacology

Antidiarrheals are a group of medications that are used to treat diarrhea, which is characterized by loose, watery stool, or an increased frequency of bowel movement.

Now, based on their mechanism of action, antidiarrheals can be broadly divided into four main groups: opiates and opiate-related agents, somatostatin analogues, adsorbents, and bulk-forming agents.

Let’s start with opioids like loperamide, diphenoxylate, difenoxin, and paregoric. These are taken orally and work by stimulating the opioid receptors found in the intestinal wall, which decreases peristalsis or bowel movement.

The slowed transient time allows for increased absorption of fluid and electrolytes into the fecal mass.

Next, there are somatostatin analogues, such as octreotide. This can be administered orally, subcutaneously, intramuscularly, or intravenously, and it’s mostly used to treat diarrhea associated with certain tumors or chemotherapy.

The way octreotide works is by binding to somatostatin receptors and mimicking somatostatin’s effects.

These include inhibiting hormone release by the pancreas and gastrointestinal tract, as well as slowing down peristalsis and decreasing the secretion of fluid and electrolytes into the bowel lumen.

Moving on to adsorbents, these include bismuth subsalicylate, and are taken orally. Once in the intestinal lumen, bismuth subsalicylate has protective properties, since it can coat the walls of the intestines, as well as antimicrobial properties, since it can kill causative bacteria.

In addition, bismuth subsalicylate has antisecretory actions, so it helps reduce how much fluid is secreted into the bowel lumen.