Chapter 34 Review

What are the consequences of chronic and acute diarrhea?

Acute diarrhea is associated with the production of loose stools in otherwise healthy individuals that lasts less than 14 days. Diarrhea that lasts more than 30 days is defined as chronic and is accompanied by weight loss, muscle weakness, and electrolyte imbalance.

How do the adsorbent antidiarrhealsdiffer from the opiates?

Adsorbent antidiarrheals exert a local action by complexing with the irritant so that it is excreted in the feces. Opiate derivatives must be distributed within gastrointestinal tissues for the drug molecules to interact with receptors or smooth muscle fibers and induce antispasmodic action.

Define adsorbents.

Adsorbents are substances that have the ability to attach other substances to their surface.

Differentiate between laxatives and cathartics.

Both laxatives and cathartics stimulate defecation. However, while laxatives produce mild, gentle stimulus, cathartics produce more intense bowel action.

How do voluntary control and the autonomic nervous system affect the process of defecation?

Defecation is under voluntary control to some extent. Individuals may force defecation by increasing abdominal pressure through muscle contraction or may inhibit defecation by voluntarily constricting anal sphincters. Defecation can be enhanced or inhibited by changes in the autonomic nervous system. Parasympathetic stimulation directly increases intestinal motility, whereas sympathetic stimulation decreases motility. Emotional stress can alter bowel activity through the autonomic nervous system.

What is diarrhea? What are the primary causes of diarrhea?

Diarrhea is a symptom of increased intestinal activity, resulting in loose, watery, unformed stools. Acute diarrhea is usually self-limiting when individuals are in good health but have encountered some irritant, infection, or emotional stress that has increased intestinal motility. Chronic diarrhea is usually accompanied by weight loss, muscle weakness, and electrolyte imbalance because continued intestinal stimulation does not permit proper reabsorption of water and essential ions before defecation occurs.

What is the mechanism of action of diphenoxylate?

Diphenoxylate is a narcotic derivative that interacts with cholinergic and opiate receptors in the body to decrease intestinal motility.

What are the various types of laxatives? How do they differ?

Laxatives can be stimulants, swelling agents, osmotic (saline) agents, or emollients. Stimulants directly irritate the intestinal mucosal lining and cause the local release of histamine. Swelling agents are natural fibers that remain in the intestine, soak up water, and distend the intestinal wall to stimulate defecation. Osmotic (saline) agents attract water into the intestine to soften the stool for easier defecation. Emollients permit water to penetrate the stool and facilitate defecation by their oily nature.

Define osmosis.

Osmosis is the process in which water moves across membranes following the movement of sodium ions.

Why are the osmotic laxatives potentially dangerous?

Osmotic laxatives usually contain sodium and magnesium ions that are absorbed and excreted through the kidneys. An increase in the sodium load may be harmful to patients who have impaired renal function, edema, or congestive heart failure. In sensitive patients, magnesium ions may depress CNS and muscle function.

Define peristalsis.

Peristalsis is characteristic intestinal movement in which circular contraction and relaxation propel the contents forward toward the rectum.

What are the primary causes of constipation?

Poorly developed toilet habits, such as ignoring the intestinal stimulus to defecate (rectal distention) or voluntary retention of feces, may result in constipation. Diets low in fiber also contribute to the development of constipation.

What agents are used for the treatment of simple diarrhea?

Simple diarrhea is associated with increased intestinal activity not due to bacterial or protozoal infections that would respond to antimicrobial therapy. Such nonspecific diarrhea is stopped by the use of anticholinergic narcotic derivatives such as diphenoxylate and loperamide or adsorbents (kaolin, pectin, bismuth salts).