Irritable Bowel Syndrome (cont.)
Medical Author:
Jay W. Marks, MD
Jay W. Marks, MDJay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles. Medical Editor:
Bhupinder Anand, MD
Medical Editor:
William C. Shiel Jr., MD, FACP, FACR
William C. Shiel Jr., MD, FACP, FACRDr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology. In this Article
 What is in the future for irritable bowel syndrome (IBS)?The future of IBS depends on our increasing knowledge of the processes (mechanisms) that cause IBS. Acquiring this knowledge, in turn, depends on research funding. Because of the difficulties in conducting research in IBS, this knowledge will not come quickly. Until we have an understanding of the mechanisms of IBS, newer treatments will be based on our developing understanding of the normal control of gastrointestinal function, which is proceeding more rapidly. Specifically, there is intense interest in intestinal neurotransmitters, which are chemicals that the nerves of the intestine use to communicate with each other. The interactions of these neurotransmitters are responsible for adjusting (modulating) the functions of the intestines, such as contraction of muscles and secretion of fluid and mucus. 5-hydroxytriptamine (5-HT or serotonin) is a neurotransmitter that stimulates several different receptors on nerves in the intestine, including one called the 5-HT4 receptor. Stimulation of these receptors by 5-HT increases muscle contractions in the colon. An example of an experimental drug that affects intestinal neurotransmission is tegaserod. This drug mimics the effect of 5-HT on the 5-HT4 receptor. Thus, because it increases intestinal muscle contractions, tegaserod is being tested for effectiveness in treating constipation-predominant IBS as well as constipation in general. Another drug that affects neurotransmission is ondansetron. This drug blocks a different receptor, the 5-HT3 receptor, and thereby reduces colonic contractions. Thus, ondansetron (Zofran) has been effective in treating diarrhea-predominant IBS in initial studies. There are drugs that stimulate another receptor, the 5-HT1 receptor. Examples of this type of drug are sumatriptan (Imitrex) and buspirone (Buspar). These drugs are believed to reduce the responsiveness (sensitivity) of the sensory nerves to what's happening in the intestine. The 5-HT1 receptor stimulators, however, have not yet been tested for effectiveness in IBS. In preliminary studies, fedotozine has been shown to improve functional gastrointestinal symptoms. The mechanism of action of fedotozine is not known, but it also may act by reducing the sensitivity of the sensory nerves. Finally, there is the issue of a relationship between IBS and intestinal bacteria. Over the next few years, much information will accumulate on this potential relationship. REFERENCE: Reviewed by William C. Shiel Jr., MD, FACP, FACR on 9/18/2012 Patient CommentsViewers share their comments
Irritable Bowel Syndrome - Diagnosis
Question: How was the diagnosis of your irritable bowel syndrome established?
Irritable Bowel Syndrome (IBS) - Treatments
Question: What was your treatment for irritable bowel syndrome?
Irritable Bowel Syndrome (IBS) - Symptoms
Question: What symptoms do you have with IBS, and are there certain triggers?
Irritable Bowel Syndrome (IBS) - Diet
Question: What dietary changes have you made to manage your IBS, and what foods seem to make it worse?
Irritable Bowel Syndrome (IBS) - SIBO
Question: Have you been tested for SIBO? If so, was it positive or negative and how was it treated?
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