Alosetron (Lotronex) effective for IBS?


Topic: Irritable Bowel Syndrome (IBS), June 2000

Dr. Lee:
Is alosetron effective in treating IBS?

Dr. Marks:
Lotronex is the brand name for alosetron, the drug which is specifically for women with irritable bowel syndrome who have diarrhea. It probably will be a model for future drugs in irritable bowel syndrome, and I think it is worthwhile to discuss the way in which it works. The nerves of the bowel, like other nerves, communicate with each other using chemical messengers or neurotransmitters. Nerves manufacture neurotransmitters and release them. They travel and attach to other nearby nerves and change the way the nearby nerves function.

One of the theories for explaining irritable bowel syndrome is that the nerves of the bowel are not functioning correctly. Since the neurotransmitters control nerve function, it is hoped that by augmenting or blocking the appropriate neurotransmitter, normal function will be restored to the nerves. For example, alosetron blocks the attachment of one neurotransmitter, 5 hydroxytryptamine, to nerves.

Dr. Lee:
I have several women patients who experienced dramatic relief of their cramps and diarrhea with low doses of alosetron. These women have had IBS for years and have failed all other treatments. For them this drug is an absolute god-send.

On the other hand, I also have patients whose bloating, diarrhea and cramps did not respond to alosetron. Some of them developed severe and bothersome constipation even with low doses of the drug. Has this been your experience too with this drug?

Dr. Marks:
I think that is true, and that is what the studies have shown so far, but that is not at all surprising because we are dealing with a very complex disorder in which there are many different types of functional problems that might be present. But the origins, that is, what is causing those problems, may result in the same kinds of symptoms, for example, abdominal pain or bloating.

Dr. Lee:
I have also tried using alosetron in men with chronic symptoms of diarrhea and cramps. So far I haven't had much success. Do you use this drug in men?

Dr. Marks:
Well, in the 2 large trials that were done with alosetron, men did not participate because they do not benefit from the treatment. It's use is approved only for women, and only in women with diarrhea.

You don't want to use alosetron on women patients with constipation because the drug's main side effect is constipation. So if a patient has constipation as part of their irritable bowel it could get worse with alosetron. There even are reports of more serious complications from alosetron such as ischemic colitis and rupture of the colon that require surgery.

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