What medications are used to treat diarrhea?
Absorbents are compounds that absorb water. Absorbents that are taken orally bind water in the small intestine and colon and make diarrheal stools less watery. They also may bind toxic chemicals produced by bacteria that cause the small intestine to secrete fluid; however, the importance of toxin binding in reducing diarrhea is unclear.
The two main absorbents are attapulgite (a naturally occurring complex mineral) and polycarbophil (a fiber) both available without prescriptions. Psyllium, another absorbent has been used for mild diarrhea, but is primarily used for constipation.
Examples of products containing attapulgite are:
- Kaopectate Advanced Formula,
- Parepectolin, and
Examples of products containing polycarbophil are:
- Konsyl Daily Fiber Therapy,
- Mitrolan, and
Products containing polycarbophil have been used to treat both diarrhea and constipation. Attapulgite and polycarbophil remain in the intestine and, therefore, have no side effects outside of the gastrointestinal tract. They may occasionally cause constipation and bloating. One concern is that absorbents also can bind medications and interfere with their absorption into the body. For this reason, it often is recommended that medications and absorbents be taken several hours apart so that they are physically separated within the intestines.
Anti-motility medications are drugs that relax the muscles of the small intestine and/or the colon. Relaxation results in slower flow of intestinal contents. Slower flow allows more time for water to be absorbed from the intestine and colon and reduces the water content of stool. Cramps, due to spasm of the intestinal muscles, also are relieved by the muscular relaxation.
The two main anti-motility medications are loperamide (Imodium), which is available without a prescription, and diphenoxylate (Lomotil), which requires a prescription. Both medications are related to opiates (for example, codeine) but neither has the pain-relieving effects of opiates.
Loperamide (Imodium), though related to opiates, does not cause addiction.
Diphenoxylate is a man-made medication that at high doses can be addictive because of its opiate-like, euphoric (mood-elevating) effects. In order to prevent abuse of diphenoxylate and addiction, a second medication, atropine, is added to loperamide in Lomotil. If too much Lomotil is ingested, unpleasant side effects from too much atropine will occur.
Loperamide and diphenoxylate are safe and well-tolerated. There are some precautions, however, that should be observed.
- Anti-motility medications should not be used without a doctor's guidance to treat diarrhea caused by moderate or severe ulcerative colitis, C. difficile colitis, and intestinal infections by bacteria that invade the intestine (for example, Shigella). Their use may lead to more serious inflammation and prolong the infections.
- Diphenoxylate can cause drowsiness or dizziness, and caution should be used if driving or if tasks that require alertness and coordination are required.
- Anti-motility medications should not be used in children younger than two years of age.
- Most unimportant, acute diarrhea should improve within 72 hours. If symptoms do not improve or if they worsen, a doctor should be consulted before continuing treatment with anti-motility medications.
Many bismuth-containing preparations are available around the world. Bismuth subsalicylate (Pepto-Bismol) is available in the US. It contains two potentially active ingredients, bismuth and salicylate (aspirin). It is not clear how effective bismuth compounds are, except in traveler's diarrhea and the treatment of H. pylori infection of the stomach where they have been shown to be effective. It also is not clear how bismuth subsalicylate might work. It is thought to have some antibiotic-like properties that affect bacteria that cause diarrhea. The salicylate is anti-inflammatory and could reduce secretion of water by reducing inflammation. Bismuth also might directly reduce the secretion of water by the intestine.
Pepto-Bismol is well-tolerated. Minor side effects include darkening of the stool and tongue. There are several precautions that should be observed when using Pepto-Bismol.
- Since it contains salicylate, a chemical related to aspirin (acetyl salicylate), patients who are allergic to aspirin should not take Pepto-Bismol.
- Pepto-Bismol should not be used with other aspirin-containing medications since too much aspirin may be ingested and lead to aspirin toxicity, the most common manifestation of which is ringing in the ears.
- The salicylate in Pepto-Bismol, similar to aspirin, can accentuate the effects of anticoagulants, particularly warfarin (Coumadin), and lead to excessive bleeding. It also may cause abnormal bleeding in people who have a tendency to bleed because of genetic disorders or underlying diseases, for example, cirrhosis that also may cause abnormal bleeding.
- The salicylate in Pepto-Bismol can aggravate stomach and duodenal ulcer disease like asiprin.
- Pepto-Bismol and salicylate-containing products should not be given to children and teenagers with chickenpox, influenza, and other viral infections because they may cause Reye's syndrome. Reye's syndrome is a serious illness affecting primarily the liver and brain that can lead to liver failure and coma, with a mortality rate of at least 20%.
- Pepto-Bismol should not be given to infants and children younger than two years of age.