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pronounced as (al oh' se tron)


Alosetron may cause serious gastrointestinal (GI; affecting the stomach or intestines) side effects including ischemic colitis (decreased blood flow to the bowels) and severe constipation that may need to be treated in a hospital and may rarely cause death. Tell your doctor if you are constipated now, if you often have constipation, or if you have had problems resulting from constipation. Also tell your doctor if you have a blockage in your bowels, ischemic colitis, blood clots, or any disease that causes inflammation of the bowels such as Crohn's disease (swelling of the lining of the digestive tract), ulcerative colitis (a condition which causes swelling and sores in the lining of the colon [large intestine] and rectum), diverticulitis (small pouches in the lining of the large intestine that can become inflamed) or liver disease. Your doctor will probably tell you not to take alosetron.

Tell your doctor and pharmacist what other prescription and nonprescription medications you are taking or plan to take . Taking certain medications during your treatment with alosetron increases the risk of serious gastrointestinal side effects. Stop taking alosetron and call your doctor right away if you experience any of the following symptoms: constipation, new or worse pain in the abdomen (stomach area), or blood in your bowel movements. Call your doctor again if your constipation does not get better after you stop taking alosetron. Once you have stopped taking alosetron because of these symptoms, do not start taking it again unless your doctor tells you that you should.

Your doctor or pharmacist will give you the manufacturer's patient information sheet (Medication Guide) before you begin treatment with alosetron and each time you refill your prescription. Read the information carefully and ask your doctor or pharmacist if you have any questions. You also can obtain the Medication Guide from the Food and Drug Administration (FDA) website ( or the manufacturer's website.

Talk to your doctor about the risks of taking alosetron.

Why is this medication prescribed?

Alosetron is used to treat diarrhea, pain, cramps, and the feeling of an urgent need to have bowel movements caused by irritable bowel syndrome (IBS; a condition that causes stomach pain, bloating, constipation, and diarrhea) in women who have diarrhea as their main symptom and have not been helped by other treatments. Alosetron is in a class of medications called 5-HT3 receptor antagonists. Alosetron works by slowing the movement of stool (bowel movements) through the intestines.

How should this medicine be used?

Alosetron comes as a tablet to take by mouth. It is usually taken twice a day with or without food. Take alosetron at around the same times every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take alosetron exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

Your doctor will probably start you on a low dose of alosetron. Your doctor will want to talk to you after you have taken the low dose for 4 weeks. If your symptoms are not controlled but you are not experiencing serious side effects of alosetron, your doctor may increase your dose. If you take the increased dose for 4 weeks and your symptoms are still not controlled, alosetron is not likely to help you. Stop taking alosetron and call your doctor.

Alosetron may control IBS but will not cure it. If alosetron helps you and you stop taking it, your IBS symptoms may return within 1 or 2 weeks.

Other uses for this medicine

Alosetron should not be prescribed for other uses; ask your doctor or pharmacist for more information.

What special precautions should I follow?

Before taking alosetron,

  • tell your doctor and pharmacist if you are allergic to alosetron, any other medications, or any of the ingredients in alosetron tablets. Ask your pharmacist for a list of the ingredients..
  • Some medications should not be taken with alosetron. Other medications may cause dosing changes or extra monitoring when taken with alosetron. Make sure you have discussed any medications you are currently taking or plan to take before starting alosetron with your doctor and pharmacist. Before starting, stopping, or changing any medications while taking alosetron, please get the advice of your doctor or pharmacist .
  • The following nonprescription or herbal products may interact with alosetron: cimetidine (Tagamet HB). Be sure to let your doctor and pharmacist know that you are taking this medication before you start taking alosetron. Do not start this medication while taking alosetron without discussing with your healthcare provider.
  • tell your doctor if you have or have ever had the conditions listed in the IMPORTANT WARNING section or any other medical problems.
  • tell your doctor if you are pregnant or plan to become pregnant. If you become pregnant while taking alosetron, call your doctor.
  • tell your doctor if you are breastfeeding. If you breastfeed while taking alosetron, monitor the breastfed infant carefully for constipation or bloody stools,

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do if I forget a dose?

Do not take a missed dose when you remember it. Skip the missed dose and take the next dose at the regularly scheduled time. Do not take a double dose to make up for a missed one.

What side effects can this medication cause?

Alosetron may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • upset stomach
  • nausea
  • gas
  • swelling in the stomach area
  • hemorrhoids

Some side effects can be serious. If you experience any of the symptoms listed in the IMPORTANT WARNING section, stop taking alosetron and call your doctor immediately.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( or by phone (1-800-332-1088).

What should I know about storage and disposal of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from light, excess heat and moisture (not in the bathroom).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website ( for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach.

In case of emergency/overdose

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

What other information should I know?

Keep all appointments with your doctor.

Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

Brand names

  • Lotronex®
Last Revised - 11/15/2023