Antidiarrheals

http://evolve.elsevier.com/Edmunds/NP/

Class	Subclass	Generic Name	Trade Name
Antidiarrheals	Opiate and opioid derivatives	diphenoxylate hydrochloride and atropine sulfate	Lomotil, OTC
		loperamide hydrochloride	Imodium, Imodium A-D,OTC
		tincture of opium, paregoric
	Antisecretory	bismuth subsalicylate	Pepto-Bismol, Pink Bismuth, OTC
	Adsorbents	attapulgite	Kaopectate, Rheaban, OTC
Oral rehydration solution (ORS)		electrolyte solution	Pedialyte, Gatorade, OTC

Key drug chosen based on common usage.

INDICATIONS

• Acute nonspecific diarrhea

• Chronic diarrhea

• Loperamide: for management of acute or traveler’s diarrhea

• Attapulgite: mild to moderate diarrhea

• Bismuth: indigestion, nausea, control of traveler’s diarrhea, and as an adjunct to treatment of Helicobacter pylori peptic ulcer disease

• Oral rehydration solution (ORS): diarrhea in all patients, especially children and pregnant women

Antidiarrheal agents are used as temporary adjunct therapy in the management of acute nonspecific diarrhea and functional chronic diarrhea. Acute episodes of diarrhea are usually benign and self-limiting, by definition lasting less than 2 weeks and usually lasting only 1 to 2 days.

Diarrhea in pregnant women and in infants can have serious consequences, and the patient may need to be referred.

If diarrhea persists for longer than 72 hours, or if gross blood is present in the stool, the patient should be evaluated further. Diarrhea should always be evaluated before pharmacologic treatment is begun. Diarrhea is a symptom, so therapy should be targeted at treatment of the underlying cause.

Many antidiarrheal agents are now available OTC and therefore may be overused. Opioid agents may prolong acute infectious diarrhea, leading to potentially serious consequences. Antidiarrheals should never be used for longer than 48 hours without supervision by a health care provider. Short-term use generally is considered safe but should not serve as a substitute for determining the cause of the diarrhea. The American Gastroenterological Association 1999 guidelines form the basis for the recommendations provided in this chapter.

Therapeutic Overview

Anatomy and Physiology

See Chapter 28 for anatomy and physiology of the bowel.

Pathophysiology

Large-volume diarrhea is caused by excessive quantities of water or secretions in the intestines. Small-volume diarrhea is caused by excessive intestinal motility.

Large-volume diarrhea can be caused by osmosis. A nonabsorbable substance (such as lactose or nonabsorbable sugar) in the gut causes fluid to be drawn into the lumen by osmosis. This condition also may be caused by excessive mucosal secretions. Bacterial toxins and neoplasms that produce hormones also stimulate secretions. Large-volume diarrhea also can be caused by excessive motility of the intestine. Conditions that affect autonomic nervous system control of digestion (e.g., diabetic neuropathy) increase transit time, thereby preventing adequate absorption of water and electrolytes from the feces.

Small-volume diarrhea usually is caused by an inflammatory condition that affects the gut mucosa.

Disease Process

Worldwide, diarrhea is a major cause of morbidity and mortality, especially in children. Diarrhea is the second most common illness among families in the United States, with an annual incidence of up to 63% per year; 4% to 20% of chronic diarrhea results from laxative abuse.

Medically, stools are classified as diarrhea if the patient has increased frequency, which usually is defined as more than two or three bowel movements per day, and the stools are liquid, not just “soft.” The emphasis in diagnosis is on consistency, not frequency.

Diarrhea is categorized as acute or chronic. By definition, acute diarrhea persists for less than 2 weeks—usually, a few days to 1 week. It can be subdivided into noninflammatory or inflammatory diarrhea. Noninflammatory diarrhea is watery and nonbloody and usually is caused by a bacterium or a virus that is self-limiting. Inflammatory diarrhea consists of WBCs in the stool; these reflect invasion of the organism or toxin into the wall of the intestine (Table 29-1).

TABLE 29-1

Causes of Acute Infectious Diarrhea

Cause	Noninflammatory	Inflammatory
VIRAL	Norwalk, rotavirus	Cytomegalovirus
PROTOZOAL	Giardia, Cryptosporidium
BACTERIAL Preformed toxin Enterotoxin production Mucosal innervation	Staphylococcus aureus, Bacillus cereus E. coli, Vibrio cholerae	Escherichia coli, Vibrio parahaemolyticus, Clostridium difficile, C. perfringens Shigella, Campylobacter jejuni, Salmonella, enteroinvasive E. coli, Chlamydia, Neisseria, Listeria

Chronic diarrhea has an extensive number of etiologies (Table 29-2). Evaluate the patient carefully for the cause of the diarrhea, and treat the disease, not the symptom. Medications that can cause diarrhea include laxatives, antacids, magnesium-containing products, and antibiotics.

TABLE 29-2

Causes of Chronic Diarrhea

Lactose intolerance

Irritable bowel disease

Fecal impaction

Inflammatory bowel disease

Ulcerative colitis

Crohn disease

Microscopic colitis

Malignancy

Radiation

Malabsorption