There are two types of antidiarrheal drugs, those that thicken the stool and those that slow intestinal spasms.

Thickening mixtures (such as psyllium) absorb water. This helps bulk up the stool and make it more firm.

Antispasmodic antidiarrheal products slow the spasms of the intestine. Loperamide (the active ingredient in products such as Imodium A-D and Pepto Diarrhea Control) is an example of this type of preparation. Some products contain both thickening and antispasmodic ingredients.

Antidiarrheal precautions

• Use antidiarrheals if you have diarrhea for longer than 6 hours. Do not use these medicines if you have bloody diarrhea, a high fever, or other signs of serious illness.
• Read and follow all label directions. Be sure to take the recommended dose.
• Long-term use is not recommended. To avoid constipation, stop taking antidiarrheal medicines as soon as stools thicken.
• If your child or teen gets chickenpox or flu, do not treat the symptoms with over-the-counter medicines that contain bismuth subsalicylate (such as Kaopectate and Pepto-Bismol). If your child has taken this kind of medicine and he or she has changes in behavior with nausea and vomiting, call your doctor. These symptoms could be an early sign of Reye syndrome, a rare but serious illness.
• Ask your doctor if your child younger than 12 should take these medicines.

For more information on diarrhea symptoms and treatment, see the topics Diarrhea, Age 12 and Older and Diarrhea, Age 11 and Younger.