Irritable Bowel Syndrome (cont.)

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Diarrhea medications

The most widely studied drug for the treatment of diarrhea in IBS is loperamide (Imodium). Loperamide appears to work by inhibiting (slowing down) the contractions of the muscles of the small intestine and colon. Loperamide is approximately 30% more effective than a placebo in improving symptoms in patients who have diarrhea as the predominant manifestation of their IBS. It is not clear if loperamide reduces abdominal pain. Loperamide can cause constipation. Therefore, the dose must be carefully adjusted and individualized for each patient. Alosetron (Lotronex) is used to treat diarrhea and abdominal discomfort that occurs in women with severe IBS that does not respond to other simpler treatments.

Alosetron, like tegaserod, affects the serotonin receptors. (See the discussion above of tegaserod.) Alosetron blocks the 5-HT3 receptor, a receptor that causes contractions when serotonin binds to it. Alosetron, by blocking 5-HT3 receptors, prevents serotonin from binding and thereby prevents contractions.

Alosetron was approved by the FDA in February 2000, but was withdrawn from the market in November, 2000, because of serious, life-threatening, gastrointestinal side effects. In June 2002, it was approved again by the FDA for marketing but in a restricted manner as part of a drug company-sponsored program for managing the risks associated with treatment. The use of alosetron is allowed only in women with severe, diarrhea-predominant, IBS who have failed to respond to conventional treatment for IBS.

The most common side effect with alosetron is constipation. One-quarter to one-third of patients may develop this side effect, but in only 10% (10 out of every 100 patients) will the drug need to be stopped temporarily or permanently.

A rare side effect with alosetron is severe intestinal inflammation caused by poor circulation of blood (ischemic colitis). This complication is life-threatening, may require surgery, and has even caused death in a small number of patients. Therefore, immediate medical attention should be sought if signs of ischemic colitis (rectal bleeding or a sudden worsening of abdominal pain) occur.

Medically Reviewed by a Doctor on 10/15/2014

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