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

The thickening mixtures (such as psyllium) contain clay or fruit pectin and absorb the bacteria and toxins in the intestine. They are safe because they do not go into the blood, but these products also absorb the bacteria needed for digestion. Long-term use is not advised.

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

Antidiarrheal precautions

• Diarrhea helps rid your body of an infection, so try to avoid using antidiarrheal medications for the first 24 hours. After that, use them only if cramping and pain continue and there are no other signs of illness, such as fever.
• Be sure to take a large enough dose. Take antidiarrheal preparations until your stools thicken, then stop immediately to avoid constipation.
• Replace lost body fluids. Dehydration can develop when someone, especially an infant, child, or older adult, has diarrhea. To help avoid dehydration, you can make a rehydration drink at home.
• 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 Pepto-Bismol and Kaopectate). 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's syndrome, a rare but serious illness. Ask your doctor if your child younger than 12 should take these medicines.