Drug Treatment in IBS - The Lesson of Alosteron (Lotronex)

Alosetron (Lotronex) was approved for marketing by the FDA in February, 2000, but was withdrawn from the market in November, 2000, because of serious, life-threatening, gastrointestinal side effects.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. Use of alosetron is allowed only among women with severe, diarrhea-predominant, irritable bowel syndrome (IBS) who have failed to respond to conventional treatment for IBS.

This article was written at the time alosteron was withdrawn by the FDA.

--Medical Editors, MedicineNet.com


The use of any drug, be it prescription, over-the-counter (OTC), or herbal, requires thought. The most important considerations are the benefits and the risks of taking the drug. If the potential benefit doesn't outweigh the potential risk, then the drug should not be taken. With respect to ethical drugs (prescription and OTC drugs), benefit is easier to determine than risk because drug studies are required in order for the drugs to be approved by the Federal Drug Administration (FDA) for marketing. These studies tell us how often the drug works and how well it works. The same studies usually tell us how often side effects (risk) occur. Unfortunately, unless many thousands of patients participate in the studies (which is almost never the case), uncommon side effects will not be recognized until the drug is approved and marketed to thousands of patients.

The case of alosetron provides an example of the difficulties of weighing potential risk against potential benefit of a new drug. Alosetron is a drug that was approved for treating women with irritable bowel syndrome (IBS) , who had diarrhea. Approval was based on studies of several hundreds of patients showing alosetron to be effective and with few important side effects. After approval and wide-spread use of alosetron, however, infrequent but very serious side effects (including death) were found to be associated with it's use. Ultimately, the FDA and the manufacturer removed alosetron from the market.

Prior to the removal of alosetron from the market, reports of the serious side effects began to appear, but it was not yet clear how common the serious side effects were or, in fact, whether they were due to alosetron. At that time, how was a patient to decide whether to use, or not to use alosetron? Here's where the weighing of risks versus benefits was important.

The studies that led up to FDA approval of alosetron clearly showed that it was beneficial. It had a substantial effect in reducing diarrhea in some patients, but the numbers of patients that were helped may have been small. The placebo worked in 40% of patients, alosetron in 50%. Because of the infrequency with which alosetron worked, for a patient with minimally-troublesome diarrhea, it might not have been reasonable to use alosetron until the frequency of the serious side effects were more clear. However, there are some patients with IBS and diarrhea so severe that they are house-bound for at least part of the day. For these patients, taking the drug may have been worth the potential serious side effects.

The situation with alosetron is not unique. We will see new drugs for IBS entering the market in the next few years. Each drug will face a situation similar to alosetron, and each patient and physician will have to make decisions about using the new drug. The degree of effectiveness will be known, as will the common side effects. The infrequent but serious side effects will not. We can only hope that the physician and patient's decision to use or not use the new drug will be based on carefully weighing the benefits versus the known and potential (unknown) risks, taking into account the seriousness of the illness that is being treated.

Medical Author: Jay W. Marks, M.D.


Last Editorial Review: 3/25/2002




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