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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 the irritable bowel syndrome (IBS). 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 attach to receptors on nearby nerve cells and cause changes in the activity of the nearby 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 are believed to control how pain is felt (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 of or an excessive response to serotonin. This may cause the pain, and diarrhea that is seen in patients with diarrhea-predominant IBS. Alosetron, by blocking 5-HT3 receptors, reduces the actions of serotonin. Other drugs in this class are granisetron (Kytril), ondansetron (Zofran) and dolasetron (Anzemet). Alosetron (Lotronex) was approved for marketing by the FDA in February, 2000, but was withdrawn from the market in November, 2000, because of serious, life-threatening, gastrointestinal side effects.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.

GENERIC AVAILABLE: no

PRESCRIPTION: yes

PREPARATIONS: Tablet: 0.5 and 1 mg.

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

PRESCRIBED FOR: Alosetron is approved for the treatment of diarrhea-predominant IBS in women who have failed conventional therapy for IBS.

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: Alosetron usually is prescribed as a 1 mg tablet, twice daily with or without food.

DRUG INTERACTIONS: While alosetron is being broken down and eliminated by the liver, it may affect several enzymes in the liver that are responsible for the elimination of other drugs, and, therefore, it may increase or decrease the blood levels of these other drugs. Oral contraceptives such as ethinyl estradiol (ESTINYL) and levonorgestrel (NORPLANT) are not affected by alosetron. Neither is theophylline (THEO-DUR) nor cisapride (PROPULSID). Nevertheless, few drugs have been tested and, therefore, there is a possibility that important interactions may occur with other drugs. Drugs whose levels might be affected by alosetron include isoniazid, procainamide (PRONESTYL), monoamine oxidase inhibitors (NARDIL), and hydralazine. Other drugs also may alter the way alosetron is eliminated by the liver and increase or decrease blood levels of alosetron, but the effects of these drugs on alosetron have not been tested.

PREGNANCY: There are no studies of alosetron in pregnant women. Therefore, it should be used cautiously during pregnancy.

NURSING MOTHERS: It is not known if alosetron is excreted in breast milk. Therefore, it should be used cautiously by nursing mothers.

SIDE EFFECTS: 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.

Other less common side effects include nausea, hemorrhoids, and abdominal distension.

A rare side effect that has occurred 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 the deaths of a small number of patients. Therefore, immediate medical attention should be sought if the signs of ischemic colitis (rectal bleeding or a sudden worsening of abdominal pain) occur.

Reference: FDA Prescribing Information

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