ANTIDIARRHEALS
Diarrhea refers to increased water content in the stool compared with an individual’s usual patterns. The frequency and volume of unformed stool are also increased. Food is propelled through the digestive tract by peristalsis, rhythmic contractions of muscles surrounding the digestive system. An increase in the overall rate of peristalsis along the digestive tube (called rapid gastrointestinal transit) can result in diarrhea, as there is insufficient time for water extraction from fecal material within the large intestine. Diarrhea may also be caused by osmotic attraction of water into the lumen of the gut (osmotic diarrhea), secretion of excess fluid into the gut (or decreased absorption; secretory diarrhea), and/or the exudation of fluid from an inflamed intestinal mucosal surface (exudative diarrhea).
Acute (short-term) diarrhea refers to a sudden change of bowel movements such that there is a frequent (three or more times per day) passage of voluminous loose stool for a period of less than several weeks. Some- times associated with fever, malaise, dehydration, and/or abdominal cramping or pain, acute diarrhea usually lasts for a period of several days. Bacterial, parasitic, and/or viral infections are the most common cause of acute diarrhea and are sometimes manifested after the drinking or eating of toxin-contaminated water and/or food (“food poisoning”). Diarrhea often affects individuals who travel to developing countries (“traveler’s diarrhea”), sometimes as a result of inadequate sanitation and contaminated food and water. The ingestion of numerous medications (e.g., antacids, antibiotics, antihypertensive medications, laxatives, magnesium supplements, potassium supplements, various cardiac medications) or of malabsorbed sugar found in many “sugarless” foods and drinks (e.g., fructose, lactose, mannitol, sorbitol) may also cause acute diarrhea. Chronic diarrhea refers to the physiological effects of acute diarrhea persisting for more than four weeks. Causes of chronic (long-term) diarrhea may in- clude abdominal surgery, abdominal radiation treatments, chronic use of acute diarrhea-causing medications, various endocrine diseases, circula- tory problems, neurological disease, chronic bacterial and/or parasitic infections, bowel disease, cancer of the digestive system, systemic chemo- therapy cancer treatment, food allergy syndromes, and food maldigestion or malabsorption. Overall, diarrhea may lead to overall dehydration and loss of vital electrolytes, and prompt treatment is recommended to avoid serious health problems.
Treatment of various types of diarrhea may include the use of oral over-the-counter liquid, tablet, caplet, or chewable tablet antidiarrhea agents. These generally include constipating agents, absorbents, and anti- secretory agents (e.g., bismuth salts). Constipating agents, such as opiates, affect the circular and longitudinal muscles of the intestine, increasing muscle tone while slowing the passage of stool through the intestine. This allows for increased water and salt reabsorption time, along with in- creased fecal consolidation and dehydration. Opiates may also elicit effects through central nervous system (brain and spinal cord) opioid re- ceptors or by decreasing intestinal fluid secretion. These agents include diphenoxylate and loperamide, both structurally related to 4-phenylpiperidine opioid analgesics (pain relievers), but have negligible opiate effects and a low abuse potential.
Absorbents, such as kaolin (a hydrated aluminum silicate clay mineral), pectin (a complex carbohydrate often extracted from fruits), and atta- pulgite (a hydrated magnesium aluminum silicate clay mineral), form a thickening powder that absorbs excess fluid and any bacterial toxins present (action of kaolin and attapulgite) and increases the consistency of the stool by forming a viscous colloidal solution (action of pectin). How- ever, these agents may also absorb essential body enzymes and nutrients.
Many types of bismuth mineral salts (e.g., bismuth subsalicylate) are generally multipurpose intestinal medicinal agents. As an antisecretory agent, bismuth subsalicylate coats and protects irritated and inflamed intestinal lumen tissue (antiulcer actions), decreases the secretion of fluid into the intestine, absorbs or neutralizes bacterial toxins, inhibits any bacterial activity (antidiarrhea actions), and also increases alkaline secretion to counteract any acid production (antacid action). Thus, this agent controls the frequent voluminous loss of watery stools while relieving intestinal cramping and irritation.
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