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Diarrhea Medications


About antidiarrheals

Antidiarrheals are medications used to treat persistent diarrhea. Diarrhea is defined as having loose, watery stools more than three times in a single day. It is a symptom of many conditions and infections and sometimes a side effect of certain medications.

In most cases, diarrhea requires no special treatment and will subside on its own after a day or two. Patients merely need to be sure to drink plenty of fluids to avoid dehydration.

However, sometimes diarrhea is persistent, leading patients to seek out medications. Diarrhea that results from viral infection and other sources, such as surgery or chemotherapy treatment for cancer, may be treated with antidiarrheals. Antidiarrheal medications work in one of two ways – they either thicken the stool or slow spasms that occur in the intestines.

The two chief antidiarrheals – bismuth subsalicylate and loperamide – are available without a prescription (although capsules of loperamide are available by prescription only). Bismuth subsalicylate works by balancing the movement of fluid through the bowels. It also kills germs and binds bacterial toxins, making them less harmful. Loperamide works by slowing both the movement of the intestines and the movement of fluid through the bowels.

In other cases, prescription drugs may be used. Drugs such as diphenoxylate increase intestinal transit time. Antispasmodics can relieve diarrhea by decreasing peristalsis, the series of coordinated, rhythmic muscle contractions that move food through the digestive tract. Other drugs that may be prescribed for persistent diarrhea include opioids and codeine.

In addition, medications and supplements usually considered laxatives may sometimes be used. Psyllium and methylcellulose, typically used as bulking agents for chronic constipation, may relieve some cases of chronic diarrhea.

It is important to note that medications such as loperamide or diphenoxylate may be used only for the symptomatic treatment of patients with acute diarrhea in whom fever is absent or low grade and stools do not contain blood.

Antidiarrheals are not recommended for diarrhea caused by infection with bacteria or a parasite. In such cases, medicine is likely to trap the organism in the intestines and actually prolong the diarrhea. Physicians may prescribe certain antibiotics instead of antidiarrheals for such types of diarrhea.

Types of diarrhea treated with antibiotics include traveler's diarrhea, which occurs from ingesting contaminated food or drink, usually while traveling, and those types caused by certain bacteria (e.g., shigellosis, cholera). Antibiotics are also used to treat significant diarrhea in children and elderly people, and in people with illnesses such as cancer, suppressed immune systems or heart disease.

Antibiotics should not be prescribed for certain conditions, such as diarrhea-associated E. coli 0157:H7 as they may predispose the patient to a condition called hemolytic uremic syndrome (HUS), which is associated with kidney failure.

Antidiarrheals are available in liquid, tablet or capsule forms. Persistent diarrhea that lasts longer than a couple of days after treatment or that is accompanied by fever, or blood or mucus in the stools is often the sign of an underlying illness. Patients who experience such chronic diarrhea should seek medical attention.

In addition, patients who have diarrhea are at high risk of dehydration, which can have severe health consequences. For this reason, it is important to drink plenty of fluids while taking antidiarrheals. Infants and children with diarrhea may avoid dehydration by drinking commercially available oral electrolyte solutions. Patients who experience any of the following symptoms of dehydration should notify their physician:

  • Decreased urination
  • Dizziness and lightheadedness
  • Dryness of mouth
  • Increased thirst
  • Newly wrinkled skin

Types and differences of antidiarrheals

The major medications used as antidiarrheals include:

Generic Name Brand Name(s) Type


Kaopectate II
Maalox Anti-Diarrheal
Pepto Diarrhea Control

Nonprescription (capsule form available by prescription only)

bismuth subsalicylate

Pepto Bismol





In some cases, drugs such as opioids and codeine may be prescribed to treat diarrhea.


Conditions of concern

Before taking antidiarrheals, patients should inform their physician if they have a fever or mucus or blood in their stools. In addition, patients with a history of liver or kidney disease may not be good candidates for antidiarrheals.

Patients who have any of the following conditions may not be good candidates for treatment with the antidiarrheal medicine bismuth subsalicylate:

  • Stomach ulcer. Ulcer or open sore in the lining of the stomach.
  • Dysentery. Infection of the colon characterized by severe, bloody diarrhea.
  • Gout. Painful form of arthritis that usually affects single joints, most often in the feet.
  • Hemophilia. Disorder that causes clotting problems or other bleeding problems.

Patients with colitis or dysentery may not be good candidates for treatment with loperamide.

Psyllium and methylcellulose should not be taken by patients experiencing abdominal pain, nausea or vomiting. Patients should also avoid these drugs if they have signs of appendicitis, intestinal obstruction or ulceration, or swallowing difficulties. Diphenoxylate should not be used by patients who have certain types of diarrhea and patients with narcotic dependence or acute ulcerative colitis.

Side effects

Potential side effects

Side effects associated with the antidiarrheal medication bismuth subsalicylate are rare, although some patients may experience a darkish tongue or grayish-black stools until they stop taking the medication. Patients who use bismuth subsalicylate should notify a physician if they experience any of the following:

  • Severe constipation
  • Severe or continuing diarrhea
  • Severe or continuing nausea and vomiting
  • Severe or continuing stomach pain
  • Anxiety
  • Loss of hearing
  • Confusion
  • Difficulty speaking or slurred speech
  • Dizziness or lightheadedness
  • Severe drowsiness
  • Fast or deep breathing
  • Severe or continuing headache
  • Increased sweating
  • Increased thirst
  • Mental depression
  • Muscle spasms, particularly in the face, neck and back
  • Muscle weakness
  • Ringing or buzzing in the ears
  • Trembling
  • Uncontrollable flapping movements of the hands (especially in elderly patients)
  • Other uncontrolled body movements
  • Vision problems

Side effects are also rare in those using loperamide, although patients may experience dryness of mouth, dizziness or drowsiness. However, patients who are taking loperamide should consult a physician if they experience any of the following side effects:

  • Bloating
  • Constipation
  • Severe stomach pain with nausea and vomiting
  • Loss of appetite
  • Skin rash

Other side effects associated with antidiarrheals include:

  • Abdominal cramps
  • Central nervous system (CNS) effects such as drowsiness and headache
  • Rapid heart rate (tachycardia)
  • Prolonged dilation of the pupil (mydriasis)
  • Dry mouth
  • Urine retention
  • Skin itchiness or rash

Drug or other interactions

Patients who are candidates for taking bismuth subsalicylate should inform their physician of any history of unusual or allergic reaction to any salicylates, including aspirin. Patients taking either bismuth subsalicylate or loperamide should report all other allergies, including those to foods, preservatives or dyes, to their physician.

Use of bismuth subsalicylate may cause increased bleeding in patients who use anticoagulants (medications that help prevent the blood from clotting). Patients who take oral antidiabetic medications may find that bismuth subsalicylate causes blood sugar levels to fall too low. Patients who take any pain medicines or anti-inflammatory medicines that contain salicylates may experience increased incidences of side effects associated with those drugs. Bismuth subsalicylate may also hamper the effectiveness of antibiotics such as tetracyclines.

Medicines that may interact poorly with bismuth subsalicylate include the gout medications probenecid and sulfinpyrazone. Other drugs that may interact poorly with bismuth subsalicylate include the following analgesic, anti-inflammatory, anti-arthritic or antipyretic medications:

  • Diclofenac
  • Diflunisal
  • Fenoprofen
  • Flurbiprofen
  • Ibuprofen
  • Indomethacin
  • Ketoprofen
  • Naproxen
  • Piroxicam
  • Sulindac
  • Suprofen

Patients who use loperamide may be at risk for severe constipation if they are also taking narcotic pain medicine. In addition, loperamide can worsen diarrhea caused by taking certain antibiotics such as erythromycins and tetracyclines.

Patients taking diphenoxylate should avoid using central nervous system (CNS) depressants (including alcohol and tranquilizers) and antidepressants such as MAO inhibitors. Both psyllium and methylcellulose can absorb other medications that are taken by the patient, blunting the effectiveness of these drugs.

How to use

Pregnancy use issues

Women who are pregnant, thinking of becoming pregnant or breastfeeding should not use antidiarrheals without first consulting a physician. Salicylates such as bismuth subsalicylate have not been shown to cause birth defects in humans, but are known to cause birth defects in animals. In addition, studies have shown that use of salicylates late in pregnancy may have undesirable effects on a newborn infant’s heart or blood flow. Use of salicylates during the final two weeks of pregnancy may cause bleeding problems in the fetus before or during delivery, whereas excessive use of salicylates during the last three months of pregnancy may result in a variety of problems for the mother. These include extended pregnancy, prolonged labor and severe bleeding before, during or following delivery.

It is not known how loperamide might affect pregnant women and their babies, although animal studies have not shown the drug to cause birth defects.

Salicylates pass into breast milk, although they do not appear to cause problems in nursing babies when taken by the mother in modest amounts. It is not known whether or not loperamide passes into breast milk.

Child use issues

Children younger than age 12 who have significant diarrhea should not use bismuth subsalicylate, and children under age 6 should not use loperamide. Instead, children under these ages who experience persistent diarrhea should be taken to a physician for medical care. Children with viral infections such as chickenpox or influenza should not take bismuth subsalicylate because of an increased risk of developing Reye syndrome, a condition in children associated with the use of aspirin and other salicylates that results in brain and liver damage.

Fluid loss caused by diarrhea can present serious health risks in children, and antidiarrheals can sometimes mask this dehydration. Fluids, including oral electrolyte solutions, can prevent dehydration. Older children with diarrhea may use antidiarrheals, but it is important that they also receive sufficient fluids to prevent dehydration.

Children who take antidiarrheals may be more sensitive to side effects than adults, especially if they have a fever or have lost large amounts of body fluid through vomiting, diarrhea or perspiration. The bismuth that is present in bismuth subsalicylate may also cause constipation in children.

Elderly use issues

Elderly patients should not take antidiarrheals without first consulting a physician because fluid loss associated with diarrhea may result in severe health problems. As with children, it is vital that elderly patients maintain a proper fluid level to avoid dehydration.

Elderly patients are more likely to suffer side effects associated with antidiarrheals than younger adults. The bismuth in bismuth subsalicylate may cause constipation in older individuals.

Symptoms of medication overdose

Symptoms of overdose will vary depending upon the type of antidiarrheal being used, but may include:

  • Central nervous system (CNS) effects such as ringing in the ears (tinnitus) and fever
  • Drowsiness
  • Low blood pressure (hypotension)
  • Seizures
  • Cessation of breathing (apnea)
  • Blurred vision
  • Excessive contraction of the eye pupils (miosis)
  • Skin flushing
  • Dryness of mouth and mucous membranes
  • Psychotic episodes
  • Constipation

Patients experiencing any of these symptoms should seek immediate medical assistance.

Questions for your doctor

Patients may wish to ask their doctor the following antidiarrheal-related questions:
  1. What are the major types of antidiarrheals? Which do you recommend for me?
  2. How will antidiarrheals work to prevent my diarrhea?
  3. Can antidiarrheals prevent all forms of diarrhea?
  4. Should I take antidiarrheal medication or just wait for my diarrhea to end?
  5. Will I experience any side effects from the antidiarrheals?
  6. Is it true that I need to be extra careful to remain hydrated when taking antidiarrheals?
  7. Given my medical history, are antidiarrheals safe for me to use?
  8. Will antidiarrheals interact with any prescription medications I’m currently taking?
  9. Are there any over-the-counter drugs I should avoid while taking antidiarrheals?
  10. For how long can I continue to safely use antidiarrheals?


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