Irritable Bowel Syndrome (IBS)
Medical Author:
Jay Marks, MD
Medical Editor:
Leslie J. Schoenfield, MD, PhD
Medical Revising Editor:
Dennis Lee, MD
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Zelnorm Back on the Market: Under Limited Use
Medical Author: Jay W. Marks, M.D.
On March 30, 2007, the FDA notified healthcare professionals and patients that Novartis had agreed to discontinue marketing tegaserod (Zelnorm) for the short–term treatment of women with irritable bowel syndrome with constipation and for patients younger than 65 years of age with chronic constipation. FDA analysis of safety data pooled from 29 clinical trials involving over 18,000 patients showed an excess number of serious cardiovascular adverse events, including angina, heart attacks, and stroke, in patients taking tegaserod (Zelnorm) compared to patients taking placebo.
Update on July 27, 2007, the FDA approved restricted use of tegaserod (Zelnorm) for patients for whom other treatment options were considered unsafe or ineffective. Use is now limited by strict criteria to patients without heart disease. Each individual patient is evaluated by Novartis under FDA supervision to ensure that he or she meets the criteria for treatment. In addition, patients who receive tegaserod (Zelnorm) are fully informed of the potential risks and benefits of using tegaserod (Zelnorm).
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What is irritable bowel syndrome (IBS)?
Irritable bowel syndrome (IBS) is one of the most common ailments of the
bowel (intestines) and affects an estimated 15% of persons in the US. The term,
irritable bowel, is not a particularly good one since it implies that the bowel
is responding irritably to normal stimuli, and this may or may not be the case.
The several names for IBS, including spastic colon, spastic colitis, and mucous
colitis, attest to the difficulty of getting a descriptive handle on the
ailment. Moreover, each of the other names is itself as problematic as the term
IBS.
IBS is best described as a functional disease. The concept of functional
disease is particularly useful when discussing diseases of the gastrointestinal
tract. The concept applies to the muscular organs of the gastrointestinal tract;
the esophagus, stomach, small intestine, gallbladder, and colon. What is meant
by the term, functional, is that either the muscles of the organs or the nerves
that control the organs are not working normally, and, as a result, the organs
do not function normally. The nerves that control the organs include not only
the nerves that lie within the muscles of the organs but also the nerves of the
spinal cord and brain.
Some gastrointestinal diseases can be seen and diagnosed with the naked eye,
such as ulcers of the stomach. Thus, ulcers can be seen at surgery, on x-rays,
and at endoscopies. Other diseases cannot be seen with the naked eye but can be
seen and diagnosed with the microscope. For example, celiac disease and
collagenous colitis are diagnosed by microscopic examination of biopsies of the
small bowel and colon, respectively. In contrast, gastrointestinal functional
diseases cannot be seen with the naked eye or with the microscope. In some
instances, the abnormal function can be demonstrated by tests, for example,
gastric emptying studies or antro-duodenal motility studies. However, these
tests often are complex, are not widely available, and do not reliably detect
the functional abnormalities. Accordingly, by default, functional
gastrointestinal diseases are those involving the abnormal function of
gastrointestinal organs in which abnormalities cannot be seen in the organs with
either the naked eye or the microscope.
Occasionally, diseases that are thought to be functional are ultimately found
to be associated with abnormalities that can be seen. Then, the disease moves
out of the functional category. An example of this would be
Helicobacter pylori infection
of the stomach. Many patients with mild upper intestinal symptoms who were
thought to have abnormal function of the stomach or intestines have been found
to have an infection of the stomach with Helicobacter pylori. This infection can
be diagnosed by seeing the bacterium and the inflammation (gastritis) it causes
under the microscope . When the patients are treated with antibiotics, the
Helicobacter, gastritis, and symptoms disappear. Thus, recognition of
Helicobacter pylori infection removed some patients' diseases from the
functional category.
The distinction between functional disease and non-functional disease may, in
fact, be blurry. Thus, even functional diseases probably have associated
biochemical or molecular abnormalities that ultimately will be able to be
measured. For example, functional diseases of the stomach and intestines may be
shown ultimately to be caused by reduced levels of normal chemicals within the
gastrointestinal organs, the spinal cord, or the brain. Should a disease that is
demonstrated to be due to a reduced chemical still be considered a functional
disease? I think not. In this theoretical situation, we can't see the
abnormality with the naked eye or the microscope, but we can measure it. If we
can measure an associated or causative abnormality, the disease probably should
no longer be considered functional.
Despite the shortcomings of the term, functional, the concept of a functional
abnormality is useful for approaching many of the symptoms originating from the
muscular organs of the gastrointestinal tract. This concept applies particularly
to those symptoms for which there are no associated abnormalities that can be
seen with the naked eye or the microscope.
While IBS is a major functional disease, it is important to mention a second
major functional disease referred to as dyspepsia, or functional dyspepsia. The
symptoms of dyspepsia are thought to originate from the upper gastrointestinal
tract; the esophagus, stomach, and the first part of the small intestine. The
symptoms include upper abdominal discomfort, bloating (the subjective sense of
abdominal fullness without objective distension), or objective distension
(swelling, or enlargement). The symptoms may or may not be related to meals.
There may be nausea with or without vomiting and early satiety (a sense of
fullness after eating only a small amount of food).
The study of functional disorders of the gastrointestinal tract often is
categorized by the organ of involvement. Thus, there are functional disorders of
the esophagus, stomach, small intestine, colon, and gallbladder. The amount of
research on functional disorders has been focused mostly on the esophagus and
stomach (such as dyspepsia), perhaps because these organs are easiest to reach
and study. Research into functional disorders affecting the small intestine and
colon (for example, IBS) is more difficult to conduct and there is less
agreement among the research studies. This probably is a reflection of the
complexity of the activities of the small intestine and colon and the difficulty
in studying these activities. Functional diseases of the gallbladder, like those
of the small intestine and colon, also are more difficult to study.
Next: What causes IBS? »
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