alosetron, Lotronex

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GENERIC NAME: alosetron

BRAND NAME: Lotronex

DRUG CLASS AND MECHANISM: Alosetron is used to treat diarrhea and abdominal discomfort that occurs in some women with irritable bowel syndrome (IBS). It works in a similar fashion as granisetron (Kytril), ondansetron (Zofran) and dolasetron (Anzemet) that are used for preventing nausea and vomiting. The discomfort and diarrhea of IBS is believed to be due to abnormal activity of the muscles of the intestines and/or the nerves that control the muscles. One of the chemical messengers which is important in coordinating the activity of intestinal nerves is serotonin. (Chemical messengers are chemicals produced and released by nerve cells that and cause changes in the activity of other nerve cells.) Alosetron belongs to a class of drugs that block one type of serotonin receptor called the 5-HT3 receptor. Serotonin and its receptors in the intestines may control pain sensation, contraction of intestinal muscle, and release of fluid into the intestines. These actions of serotonin can result in pain and diarrhea. The exact cause of IBS is unknown, but it is thought that stimuli such as food, medications, hormonal changes, or stress may trigger an excessive release or excessive response to serotonin. This may cause pain, and diarrhea seen in patients with diarrhea-predominant IBS. Alosetron, by blocking 5-HT3 receptors, reduces the actions of serotonin. Alosetron (Lotronex) was approved for marketing by the FDA in February, 2000 but was withdrawn from the market in November 2000, because of serious, life-threatening, gastrointestinal side effects.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 IBS who have failed to respond to conventional treatment for IBS.



PREPARATIONS: Tablet: 0.5 and 1 mg.

STORAGE: Tablets should be stored at room temperature, 15 C to 30 C (59 F to 86 F).

PRESCRIBED FOR: Alosetron is approved for the treatment of severe diarrhea-predominant IBS among women who have chronic IBS symptoms lasting 6 months or longer and have not adequately responded to conventional IBS treatment.

Only prescribers who have enrolled in the Prometheus prescribing program for alosetron should prescribe alosetron due to safety reasons.

In two, 12-week studies involving over 1,200 women, most of whom suffered from diarrhea-predominant IBS, 40% of the patients (or 40 out of every 100 patients) had adequate relief from abdominal pain and discomfort while taking alosetron. Thirty percent of the patients (or 30 out of every 100 patients) had adequate relief while taking placebo (a dummy pill). In addition, among the alosetron-treated patients there were fewer bowel movements accompanied by a sense of urgency, fewer daily stools, and firmer stools than among the placebo-treated patients.

DOSING: The starting dose is 0.5 mg twice daily. If constipation develops at this dose alosetron should be discontinued until the constipation resolves. It may be restarted at 0.5 mg once daily. If 0.5 mg once daily causes constipation, then alosetron should be discontinued. After 4 weeks, patients whose symptoms are not adequately controlled may receive up to 1 mg twice daily. Patients without adequate control after 4 weeks of treatment with 1 mg twice daily should discontinue alosetron. Alosetron may be taken with or without food.

DRUG INTERACTIONS: Fluvoxamine (Luvox) increases blood levels of alosetron by reducing its breakdown by the liver. Therefore, both drugs should not be combined. Ketoconzole, clarithromycin (Biaxin), itraconazole (Sporanox), and voriconzole (vfend) may also increase blood levels of alosetron.

Medically Reviewed by a Doctor on 3/18/2013

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