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Alosetron is used to treat certain women who have severe diarrhea-predominant irritable bowel syndrome (IBS-D). Alosetron works by blocking signals in the gut that affect pain, digestion, and how food moves through the colon. This helps reduce irritable bowel symptoms such as pain and diarrhea. Common side effects include constipation, stomach or gut discomfort or pain, and nausea. Stop this medicine and call your health care provider right away if you become constipated or get new or worsening stomach pain, bloody diarrhea, or blood in your stool (poop).

Uses

What is alosetron used for?

Alosetron is commonly used to treat certain women who have severe diarrhea-predominant irritable bowel syndrome (IBS-D).

Alosetron may also be used for other conditions as determined by your health care provider.

How does alosetron work (mechanism of action)?

Alosetron works by blocking signals in the gut that affect pain, digestion, and how food moves through the colon. This helps reduce irritable bowel symptoms such as pain and diarrhea.

How is alosetron supplied (dosage forms)?

Brands and other names

  • Lotronex

Dosage forms and strengths

  • 0.5 mg oral tablets
  • 1 mg oral tablets

How should I store alosetron?

Alosetron should be stored at room temperature, between 68 F and 77 F (20 C and 25 C). It can be exposed to temperatures between 59 F and 86 F (15 C and 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. Protect from light. 

Side Effects

What are the most common side effects of alosetron?

The most common side effects of alosetron are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Constipation (see below)
  • Stomach or gut discomfort or pain
  • Nausea 

There may be other side effects of alosetron that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of alosetron?

While less common, the most serious side effects of alosetron are described below, along with what to do if they happen.

Severe Allergic Reactions. Alosetron may cause allergic reactions, which can be serious. Stop taking alosetron and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Constipation. Alosetron can cause constipation, and in some cases it can lead to severe constipation. Some people have needed to go to the hospital to get blood transfusions, surgery, or other treatments. Stop taking alosetron and get help right away if you have constipation or get new or worsening stomach pain, bloody diarrhea, or blood in your stool (poop). 

Ischemic Colitis. Alosetron may cause ischemic colitis, which is a condition where your colon (large intestine) becomes inflamed or damaged due to a reduction in blood flow. Stop taking alosetron and get help right away if you have symptoms of ischemic colitis.

  • New or worsening stomach or gut pain
  • Blood in your stool (poop)
  • Bloody diarrhea 
  • Low fever, less than 100 F
  • Nausea or vomiting
  • Swollen belly 

Warnings & Precautions

Who should not use alosetron?

Allergies to Ingredients. People who are allergic to any of the following should not take alosetron.

  • Alosetron
  • Lotronex
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific alosetron products they stock.

Constipation. Alosetron should not be used if you have constipation. Alosetron can make this condition worse. 

Gut Blockage or Tear. Alosetron should not be used if you have or have a history of a blockage or tear in your gut (bowel obstruction or gastrointestinal perforation) or narrowing of the intestines. Alosetron can make these conditions worse. 

Toxic Megacolon. Alosetron should not be used if you have or have a history of toxic megacolon, which is a rare and serious condition that can cause your colon to swell, weaken, and stop working properly. Alosetron can make this condition worse. 

Ischemic Colitis. Alosetron should not be used if you have or had ischemic colitis or other blood flow problems to the bowel. Alosetron can make these conditions worse.

Blood clots. Alosetron should not be used if you have or have a history of blood clots, thrombophlebitis, or a condition where your blood is more likely to form clots than normal. Alosetron can make these worse. 

Crohn’s Disease. Alosetron should not be used if you have or have a history of Crohn’s disease, which is an inflammatory bowel disease that causes swelling and inflammation in your digestive tract. Alosetron can make this condition worse. 

Ulcerative Colitis. Alosetron should not be used if you have or have a history of ulcerative colitis, which is an inflammatory bowel disease that causes irritation, inflammation and ulcers in the colon (large intestine). Alosetron can make this condition worse. 

Diverticulitis. Alosetron should not be used if you have or have a history of diverticulitis, which is a condition where pouches in your intestines become inflamed or infected. Alosetron can make this condition worse. 

Liver Problems. Alosetron should not be used if your liver is not working as well as it should be. If there is a concern about the health of your liver, your health care provider may do tests to determine if it is working well enough to take this medicine.

Drug Interactions. Alosetron should not be taken while you are using certain other medicines. Before taking alosetron, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

What should I know about alosetron before using it?

Do not take alosetron unless it has been prescribed to you by a health care provider. Take it as prescribed.

Do not share alosetron with other people, even if they have the same condition as you. It may harm them.

Keep alosetron out of the reach of children.

People who are 65 or older or who are weak from illness can be at greater risk for some side effects from alosetron. Talk to your health care provider about your risks if you are in one of these groups.

Talk to your health care provider if you still have irritable bowel symptoms after taking alosetron for four weeks. They may adjust your dose or switch you to a different medicine.

If this medicine is stopped because of constipation, tell your health care provider if the constipation does not go away. Do not start taking alosetron again unless your constipation has gone away and your health care provider tells you to restart the medicine.

What should I tell my health care provider before using alosetron?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if alosetron is right for you.

In particular, make sure that you discuss if you have any gut or stomach problems.

Pregnancy. It is not known if or how alosetron could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if alosetron passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does alosetron interact with foods or drinks?

There are no known interactions between alosetron and foods or drinks.

It is unknown if drinking alcohol will affect alosetron.

Does alosetron interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking alosetron.

  • Fluvoxamine (Luvox), which is a medicine commonly used for obsessive-compulsive disorder (OCD)
  • Ketoconazole, which is a medicine used for fungal infections

Many other medicines may alter the blood levels of alosetron. Tell your health care provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with alosetron. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much alosetron?

If you or someone else has used too much alosetron, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of alosetron?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.