Tegaserod (Zelnorm)...New Drug for IBS (cont.)
What is IBS?
IBS is a common gastrointestinal condition. Patients with IBS typically
complain of recurrent abdominal pain, bloating, and alteration in bowel habit.
Some IBS patients are prone to constipation, some are prone to diarrhea, and
some have periods of constipation alternating with periods of diarrhea. IBS is a
chronic condition; symptoms can come and go over months, years or even decades.
IBS is a functional disorder of the intestines and its nerves; it may be
caused by either abnormal motility (abnormal contractions) of the intestinal
muscles or abnormally sensitive nerves in the intestines (visceral
hyper-sensitivity). IBS is more difficult to diagnose than diseases with
structural abnormalities. (Structural abnormalities are abnormalities that can
be "seen" by examinations such as x-ray or endoscopy such as ulcers,
infections, colitis, and cancers.)
While IBS is not life-threatening, symptoms of IBS can have a significant
impact on a person's quality of life and can even be debilitating. For example, a
patient with frequent diarrhea and an urgent need to have a bowel movement after
meals may avoid eating out; and patients who develop bloating and abdominal pain
after meals may develop a fear of eating.
What causes IBS?
The cause of abnormal intestinal motility and visceral hypersensitivity in
IBS is not precisely known. Most scientists believe that a chemical called
serotonin (also known as 5-hydroxytryptamine or 5-HT) plays an important role in
stimulating muscle contractions in the intestines and increasing the sensitivity
of the intestines to pain. For a serotonin molecule to exert these influences,
it must first attach to it's receptor. These
receptors are called 5-HT receptors, and there are several subtypes of the 5-HT
receptor, referred to as 5-HT1, 5-HT2, 5-HT3, and 5-HT4. In IBS, it is believed
that there may be either abnormal amounts of serotonin or 5-HT receptors or
abnormal binding of serotonin to the 5-HT receptors and that these abnormalities
cause most of the symptoms.
What is the traditional treatment of IBS?
Traditional treatment of IBS is directed at the symptoms, and not at the
underlying molecular or cellular abnormalities that may be responsible for IBS.
For example, constipation has been treated with fiber supplements, stool
softeners, and laxatives; diarrhea has been treated with anti-diarrhea agents
such as loperamide (Imodium) or cholestyramine powder (Questran). Abdominal pain
and cramps have been treated with anti-spasmodic agents such as
Librax, or anti-depressants in low doses
to decrease the sensitivity of the
intestines to pain. Unfortunately, most of these traditional treatments usually
are ineffective or only partially or temporarily effective in treating the
symptoms of IBS.