Chapter 40: Antidiarrheal Drugs & Laxatives

Diarrhea is defined by the abnormally frequent passage of loose stools, often requiring treatment aimed at decreasing frequency, alleviating cramping, and crucially, replenishing fluids and electrolytes, particularly since fluid replacement is often the sole necessary intervention. Antidiarrheal agents are categorized into three main groups based on their mechanism of action: adsorbents (like bismuth subsalicylate) physically coat the GI walls and bind toxins for elimination; antimotility drugs (which include anticholinergics and opiates like loperamide and diphenoxylate) reduce GI motility, increase intestinal transit time, and enhance water and nutrient absorption; and probiotics (such as Lactobacillus) re-establish the normal intestinal flora often destroyed by antibiotics. Conversely, constipation, the infrequent and difficult passage of feces, is addressed using laxatives, which promote bowel evacuation and are classified into five groups. Bulk-forming laxatives (e.g., psyllium) absorb water to increase fecal mass, simulating natural fiber; emollient laxatives (e.g., docusate sodium, mineral oil) soften the stool or lubricate the intestinal walls; hyperosmotic laxatives (e.g., polyethylene glycol, lactulose) increase water content in the feces via osmotic pressure; saline laxatives (e.g., magnesium hydroxide) increase osmotic pressure in the small intestine, drawing water into the lumen; and stimulant laxatives (e.g., senna, bisacodyl) increase peristalsis by stimulating intestinal nerves. Throughout treatment, the nursing process emphasizes careful assessment for fluid and electrolyte imbalances, particularly in vulnerable populations, recognizing that antidiarrheal drugs are contraindicated if an infectious pathogen is present, and being vigilant for laxative misuse, dependency, and the risk of Reye’s syndrome when administering bismuth subsalicylate to children recovering from viral illness.