Medically reviewed by Matthew Hamilton, MD

Taking an antidiarrheal medicine, even an over-the-counter one, can be dangerous for people with IBD, so it’s wise to do so only under the supervision of your doctor. In general, antidiarrheals should be taken for a maximum of two weeks. If you have a fever or severe pain in the abdomen, stop taking them immediately.

If you have diarrhea because your colon is moderately or severely inflamed, it’s possible to end up with toxic megacolon, a serious side effect in which the colon swells dramatically and can sometimes rupture. This is particularly a concern for people with ulcerative colitis, though it can occur in people with Crohn’s disease, as well.

Here are five common antidiarrheal medicines and what you need to know about each one.

Loperamide (Imodium®, Diamode®)

Availability: Over-the-counter or as a prescription

How It Works: Slows down the digestive process, allowing your body to better absorb food

Possible Side Effects: Dry mouth, drowsiness, constipation

Diphenoxylate (Lomocot®, Lomotil®)

Availability: Prescription

How It Works: Slows down the digestive process, allowing your body to better absorb food

Possible Side Effects: Bloating, constipation; can be addictive: considered a “controlled substance”

Cholestyramine (Prevalite®, Questran®)

Availability: Prescription, typically only prescribed to Crohn’s patients after ileal resection surgery

How It Works: Binds substances in the bile that may be causing diarrhea

Possible Side Effects: Constipation, can interfere with the absorption of other medications

Codeine Sulfate (Tylenol with Codeine®)

Availability: Prescription, typically only prescribed to Crohn’s patients also experiencing pain

How It Works: Slows down the digestive process and reduces pain

Possible Side Effects: Dry mouth, drowsiness, constipation; can be addictive: considered a “controlled substance”

Bismuth Subsalicylate (Pepto-Bismol®)

Availability: Over-the-counter

How It Works: Coats irritated stomach and intestinal tissue, slows down the digestive process

Possible Side Effects: Constipation, temporary darkening of tongue

A Final Word About Antidiarrheals

Taking an antidiarrheal might seem like an easy solution when you are in a pinch, but in certain situations it can do more harm than help. Before you pop that pill, give your doctor a call to make sure you are not going to inadvertently create a far worse situation.


With more than 4,000 articles to her credit, Tara Baukus Mello’s work has appeared in such publications as Woman’s Day, The New York Times, The Los Angeles Times, and cNet.com, among others.

Medical reviewer and Oshi physician-partner Matthew J. Hamilton, MD is an Assistant Professor of Medicine at Harvard Medical School and a specialist in Gastroenterology, Hepatology, and Endoscopy at Brigham and Women’s Hospital Crohn’s and Colitis Center in Boston. He is a leading member of the research team at the BWH Crohn’s and Colitis Center, and has garnered national recognition for his research into the underlying inflammatory processes of IBD.

Oshi is a tracking tool and content resource. It does not render medical advice or services, and it is not intended to diagnose, treat, cure, or prevent any disease. You should always review this information with your healthcare professionals.