Antidiarrheals are drugs used to treat persistent diarrhea. The two chief antidiarrheal medications are bismuth subsalicylate and loperamide. Another medication called diphenoxylate is also commonly used. These agents may be used to treat patients with acute diarrhea in whom fever is absent or low grade and stools are not bloody.

Most cases of diarrhea resolve in a few days without treatment. When diarrhea does not subside on its own in a timely manner, antidiarrheal medications may be used. Most antidiarrheal formulations are available without a prescription. In some cases, however, prescription medications used to treat other digestive disorders may also be used to treat diarrhea.

Antidiarrheal medications are available in liquid, tablet or capsule forms. They work in various ways to thicken the stool or slow spasms that occur in the intestine. For example, bismuth subsalicylate balances how fluid moves through the bowels, kills germs and binds bacterial toxins. The drug loperamide slows both the movement of the intestines and fluid as it moves through the bowels.

Although antidiarrheals may help stop a patient’s diarrhea, they may also mask dehydration, which presents significant health threats. For this reason, patients who take antidiarrheals are also urged to drink plenty of fluids. Patients should seek medical attention when diarrhea is accompanied by fever, blood or mucus in the stools, or lasts more than several days, even with treatment.