7.4: Antidiarrheal Medications and Laxatives

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Ernstmeyer & Christman (Eds.)
Chippewa Valley Technical College via OpenRN

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The digestive system is continually at work, but unless something goes amiss, you don’t notice your digestive system working. This section will focus on bowel disorders that occur in the lower intestine during the final step of digestion called defecation, when undigested materials are removed from the body as feces. During this final step, the large intestine absorbs water and changes the waste from liquid into stool; then peristalsis helps move the stool into the rectum. Diarrhea and constipation occur when conditions occur that affect this final step of defection.

The process of defecation begins when mass movements force feces from the colon into the rectum, stretching the rectal wall and provoking the defecation reflex, which eliminates feces from the rectum. This parasympathetic reflex is mediated by the spinal cord. It contracts the sigmoid colon and rectum, relaxes the internal anal sphincter, and initially contracts the external anal sphincter. Figure 7.9^{^[1]} reviews the anatomy of the rectum and its external and internal sphincters. The presence of feces in the anal canal sends a signal to the brain, which gives the person the choice of voluntarily opening the external anal sphincter (defecating) or keeping it temporarily closed. If defecation is delayed until a more convenient time, it takes a few seconds for the reflex contractions to stop and the rectal walls to relax. The next mass movement will trigger additional defecation reflexes until defecate occurs.^{^[2]}

Illustration of anorectum with labels — Figure 7.9 Anatomy of the Rectum

If defecation is delayed for an extended time, additional water is absorbed, making the feces firmer and potentially leading to constipation. Alternatively, if the waste matter moves too quickly through the intestines, not enough water is absorbed, and diarrhea can result. Figure 7.10^{^[3]} demonstrates the Bristol Stool Chart that is used to assess stool characteristics ranging from very constipated to diarrhea.

Image showing Bristol Stool Chart — Figure 7.10 Bristol Stool Chart

You can further review how the digestive system works at the following links:

Digestive System Processes and Regulation
Your Digestive System and How it Works ^{^[4]}
Video on Digesting Food ^{^[5]}

7.4a Antidiarrheals

Pathophysiology

Diarrhea is defined as the passage of three or more loose or liquid stools per day (or more frequent passage than is normal for the individual). Frequent passing of formed stools is not considered diarrhea. Diarrhea has multiple causes such as bacteria from contaminated food or water; viruses such as influenza, norovirus, or rotavirus; parasites found in contaminated food or water; medicines such as antibiotics, cancer drugs, and antacids that contain magnesium; food intolerances and sensitivities; and diseases that affect the colon, such as Crohn’s disease or irritable bowel syndrome.^{^[6]} The most severe threat posed by diarrhea is dehydration caused by the loss of water and electrolytes. Diarrheal disease is a leading cause of child mortality and morbidity throughout the world due to dehydration; frail elderly are also at risk. When severe diarrhea occurs, assessment for dehydration and electrolyte imbalances receive top priority and rehydration with oral rehydration solutions or IV fluids may be required.^{^[7]} Common medications used to manage the symptoms of diarrhea are discussed below.

Nursing Considerations

Assessment

When administering antidiarrheals, the nurse should document an abdominal assessment, frequency of bowel movements and stool characteristics, and if there is skin breakdown in the anal area. Dehydration is a serious risk in patients with severe diarrhea, so priority assessments and documentation relate to monitoring for dehydration, especially in vulnerable populations of infants, children, and elderly. If signs of dehydration occur, the provider should be immediately notified and treatment initiated for dehydration.

Implementation

Teach the patient to not exceed dosages of OTC medications because life-threatening adverse effects may occur. Probiotics have been found to be likely safe in all populations, and the nurse can advocate for the use of probiotics in patients with diarrhea or those at risk for diarrhea because of other medications prescribed. In addition to teaching about medication therapy, nurses can also teach patients with diarrhea other nonpharmacological interventions, such as replacing fluid and electrolytes by drinking water, sports drinks, or sodas without caffeine; and eating soft, bland food like bananas, rice, and toast. Children with severe diarrhea may also require oral rehydration solutions to replace lost fluids and electrolytes. The nurse should also keep in mind that antidiarrheals should be used very cautiously with children because some categories are contraindicated.

Evaluation

Because antidiarrheals treat the symptoms of diarrhea but do not eliminate the cause of it, if symptoms do not resolve within 48 hours, the provider should be notified and other potential causes of diarrhea investigated. Monitor for serious adverse effects such as increased bleeding in patients taking salicylates and for abnormal heart rhythms in patients taking loperamide and notify the provider immediately. Evaluation for dehydration should continuously occur until the condition resolves.

Antidiarrheal Medication Classes

There are three common mechanisms of action of antidiarrheal medications: adsorbents, which help eliminate the toxin or bacteria from the GI tract; antimotility agents, which slow peristalsis; and probiotics, which help to restore the normal bacteria found in the lower intestine. Oral rehydration agents may also be used in patients with diarrhea to replace fluid and electrolyte loss, but they do not treat the diarrhea. Antibacterial agents may also be used to treat diarrhea caused by specific infections, such as campylobacter or giardia, but they are not routinely needed.^{^[8]}

Adsorbents

Adsorption is the adhesion of molecules to a surface. This process differs from absorption, where a substance is dissolved or penetrates into a surface. Bismuth subsalicylate (brand name Pepto Bismol) is an example of an adsorbent (see Figure 7.11^{^[9]}).

Photo of Pepto Bismol bottle — Figure 7.11 Bismuth Subsalicylate

Mechanism of Action Adsorbent medications work by coating the walls of the GI tract and binding the causative bacteria or toxin for elimination from the GI tract through the stool.^{^[10]}Bismuth subsalicylate also decreases the flow of fluids and electrolytes into the bowel, reducing inflammation within the intestine.^{^[11]}

Specific Administration Considerations Bismuth subsalicylate contains salicylate. It should be avoided if the patient has an allergy to salicylates (including aspirin) or if the patient is taking other salicylate products such as aspirin. It should not be used if the patient has an ulcer, a bleeding problem, or bloody or black stool. Children and teenagers who have or are recovering from chicken pox or flu-like symptoms should not use this product. When using this product, if changes in behavior with nausea and vomiting occur, consult a doctor because these symptoms could be an early sign of Reye’s syndrome, a rare but serious illness. Liquid products should be shaken well before use. Tablets should be swallowed whole and not chewed unless they are a chewable tablet. Medication can cause a black or darkened tongue. If symptoms worsen, a fever, or ringing in the ears occurs, or if diarrhea lasts longer than 48 hours, contact the provider. ^{^[12],^[13]}

Patient Teaching & Education

Patients should be advised to take medication as directed. They should be aware of potential color changes to stool that may occur and that the medication contains aspirin. They should discontinue the medication if tinnitus occurs.^{^[14]}

Antimotility

Antimotility medications help to treat diarrhea by slowing peristalsis. There are two categories of antimotility medication: anticholinergics and opiate-like medication.

Anticholinergics

Mechanism of Action Hyoscyamine is an anticholinergic that works on the smooth muscle of the GI tract to inhibit propulsive motility and decreases gastric acid secretion.

Specific Administration Considerations Read drug label information for all contraindications, including but not limited to, glaucoma, myasthenia gravis, and paralytic ileus. Diarrhea may be an early symptom of incomplete intestinal obstruction, and the use of this drug would be inappropriate and possibly harmful. CNS symptoms and other adverse effects may occur that are common with anticholinergic medications.^{^[15],^[16]}

Patient Teaching & Education

Patients should receive instruction that these medications may cause dizziness and drowsiness. If patients experience dry mouth, frequent oral hygiene may alleviate discomfort.^{^[17]}

Opioid-like medication

Mechanism of Action Loperamide has an opioid-like chemical structure but causes fewer CNS effects. It works by decreasing the flow of fluids and electrolytes into the bowel and by slowing down the movement of the bowel to decrease the number of bowel movements (see Figure 7.12^{^[18]}).

Photo of Loperamide Hydrochloride Tablets — Figure 7.12 Loperamide

Specific Administration Considerations Loperamide should not be given to a child younger than two years of age because of the risk of serious breathing and heart problems. Taking more than the prescribed dose can cause a serious abnormal heart rhythm that can lead to death. Read the drug label carefully for information about interaction with other medications, especially antidysrhythmics and antipsychotics.^{^[19],^[20]}

Patient Teaching & Education

Patients should take medications as directed. They should also avoid alcohol and other CNS depressants. The medications may cause drowsiness.^{^[21]}

Probiotics

Probiotics are used for the prevention and treatment of diarrhea. They are often used concomitantly with antibiotics to prevent the common associated side effects of diarrhea (see Figure 7.13^{^[22]}). An example of a probiotic is lactobacillus.

Photo of probiotic yogurt in container. — Figure 7.13 Probiotics come in several forms

Mechanism of Action Probiotics help replenish normal bacterial flora in the gastrointestinal tract.

Specific Administration Considerations/ Patient Teaching& Education Side effects of probiotics are mild such as gas and bloating. Probiotics are safe for use in children.^{^[23],^[24]}

Now let’s take a closer look at medication grids comparing medications used to treat diarrhea. (See Table 7.4a^{^[25],^[26]}.)

Medication grids are intended to assist students to learn key points about each medication. Because information about medication is constantly changing, nurses should always consult evidence-based resources to review current recommendations before administering specific medication. Basic information related to each class of medication is outlined below. Detailed information on a specific medication can be found for free at Daily Med. On the home page, enter the drug name in the search bar to read more about the medication. Prototype/generic medications listed in the grids below are also hyperlinked directly to a Daily Med page.

Table 7.4a Comparison of Medications Used to Treat Diarrhea
Class	Prototype/Generic	Administration Considerations	Therapeutic Effects	Adverse/Side Effects
Adsorbents	bismuth subsalicylate (Pepto Bismol)	Avoid if taking other salicylates Do not use in children or teenagers recovering from chicken pox or flu-like symptoms as may cause Reye’s syndrome Do not use if patient has an ulcer, bleeding problem, or bloody or black stool	Decreased diarrhea symptoms	May cause black or darkened tongue Contact provider if symptoms worsen, a fever, or ringing in the ears occurs, or if diarrhea lasts longer than 48 hours
Anticholinergic	hyoscyamine	Contraindicated in glaucoma, myasthenia gravis, or paralytic ileus	Decreased diarrhea symptoms	May cause CNS and other adverse effects associated with anticholinergic medication
Opiate-like medication	loperamide (lmodium)	Contraindicated in children younger than 2 and with several other medications; read drug label information before administering	Decreased diarrhea symptoms	Black Box Warning: May cause abnormal heart rhythm
Probiotics	lactobacillus	Pediatric dosing is age based and varies by product	Prevention of diarrhea or decreased symptoms of diarrhea	Mild such as gas and bloating

Critical Thinking Activity 7.4a

A patient has been prescribed loperamide for diarrhea associated with gastroenteritis. The patient begins to complain of “heart palpitations.” What is the nurse’s next best response?
A child, aged 6, has diarrhea. The mother asks the nurse what OTC medications she can provide to her child to help resolve the diarrhea. What is the nurse’s best response?

Note: Answers to the Critical Thinking activities can be found in the “Answer Key” sections at the end of the book.