Prescription Medicine for Diarrhea Predominant IBS

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Although limited, there are some prescription medicines for the treatment of diarrhea predominant IBS (IBS-D) and its symptoms of severe abdominal pain and cramping, and frequent, urgent bouts of loose, watery diarrhea.

There is no cure for IBS-D, but a variety of medications may be prescribed to reduce symptoms. Remember that since IBS is a chronic condition, and medications may have side effects, it is essential to explore non-drug strategies (including mind/body treatment options and dietary modifications) in addition to taking medication.

Here is an overview of some of the options that are available to your doctor in helping you to manage your IBS:


Although commonly prescribed for the treatment of depression and anxiety, antidepressants are sometimes prescribed due to their beneficial effects on IBS symptoms. It is not yet known precisely why this positive effect occurs. It may be due to the medication having an effect on neurotransmitters found in both the brain and the gut, it may have something to do with an effect on the communication between the gut and brain in terms of the stress response, or it may have to do with the effect of these medications on the parts of the brain that are involved in stress and/or pain response. Antidepressants used for IBS tend to come from one of two classes, selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs). Learn more about antidepressants for IBS...


This class of medications targets and reduces the neurotransmitter acetylcholine in the nervous system with the result of slowing and reducing contractions of the muscles in the intestinal system. Their benefit for diarrhea predominant IBS comes from the reduction in the secretion of mucus and intestinal spasms.

This anticholinergic effect is the same as seen in the tricyclic antidepressants and thus similar side effects may be experienced. Learn more about antispasmodics for IBS...


Antibiotics are the newest potential weapons in the IBS-D arsenal. Several antibiotics have been studied due to their unique properties - they are not absorbed by the stomach and therefore are able to act on bacteria within the small and large intestine. These antibiotics are recommended for short-term use only as there is no research information yet available regarding the safety of long-term use. To date, no antibiotic has yet been approved of as a treatment for IBS. Learn more about antibiotics for IBS...

Gut-Directed 5-HT3 Medicine

A relatively new approach to understanding and treating IBS involves looking at particular neurotransmitters found in the intestinal system. Neurotransmitters are chemicals that relay information among nerve cells. The gut appears to have its own "brain" and it is this information system that is receiving attention in IBS research.

It is believed that neurotransmitters within this system are responsible for regulating the process of digestion, including muscle contractions, mucus secretion and fluid absorption. Medications that target these neurotransmitters would therefore help the system to function more effectively.

5-HT3 refers to specific receptor sites for certain neurotransmitters found within the gut. Medications in this class appear to prevent serotonin from attaching to the 5-HT3 receptors. The end result is a slowing of intestinal contractions, thereby reducing diarrhea and urgency. Lotronex, Zofran, Kytril, and Remeron are all classified as 5-HT3 medications. Of these, only Lotronex is designed specifically for the treatment of IBS-D. Zofran and Kytril are used to reduce nausea and vomiting associated with cancer treatment and Remeron is an antidepressant.

Due to the risk of serious side effects, there are strict limitations on the prescription of Lotronex. For more information, see "Lotronex for IBS-D".

Bile Acid Binders

For cases of IBS-D in which the diarrhea occurs immediately after eating some doctors are using bile acid binders as an "off label" prescription.  These medications include:


American College of Gastroenterology IBS Task Force "An Evidence-Based Position Statement on the Management of Irritable Bowel Syndrome" American Journal of Gastroenterology 2009:S1-S35.

British Society of Gastroenterology guidelines for the management of the irritable bowel syndrome(2000) Jones, J. Gut 47:ii1-ii19.

Irritable bowel syndrome: diagnosis and management (2006) Agrawal, A. & Whorwell, P.J. British Medical Journal, 332:280-283.


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