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 Donnatal or 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.