Description and Brand Names

Drug information provided by: Merative, Micromedex®

US Brand Name

  1. Lotronex


Alosetron is used to treat irritable bowel syndrome (IBS) in women who have diarrhea as their main symptom. This medicine is only used in severe cases of IBS that have not responded to other therapy. IBS is also known as irritable colon or spastic colon. IBS may be caused by a chemical called serotonin, which causes your intestinal system to be overactive. Alosetron works by blocking the action of serotonin on the intestine. This reduces the cramping abdominal pain, abdominal discomfort, urgency (sudden need for a bowel movement), and diarrhea caused by IBS. Alosetron does not cure IBS and may not help every person who takes it.

Alosetron is available through a restricted marketing program. Only doctors enrolled in the prescribing program can write a prescription for alosetron.

This product is available in the following dosage forms:

  • Tablet

Before Using

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:


Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Appropriate studies have not been performed on the relationship of age to the effects of alosetron in the pediatric population. Safety and efficacy have not been established. Because of alosetron's risk of serious side effects, use in children is not recommended.


Appropriate studies performed to date have demonstrated that older adults may have an increased risk of serious side effects (e.g., constipation) with alosetron compared to younger adults. Alosetron should be used with caution in the elderly.


There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Drug Interactions

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

  • Apomorphine
  • Fluvoxamine
  • Viloxazine

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Capmatinib
  • Cimetidine
  • Ciprofloxacin
  • Codeine
  • Gatifloxacin
  • Givosiran
  • Norfloxacin
  • Ofloxacin
  • Oxycodone
  • Pacritinib
  • Ritlecitinib
  • Tocilizumab

Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Ketoconazole

Other Interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other Medical Problems

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Blood clotting problems, severe, history of or
  • Constipation, severe, history of or
  • Diverticulitis (abnormal pouches in bowel that become inflamed), history of or
  • Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis), history of or
  • Intestinal adhesion or stricture (bowel blockage), history of or
  • Intestinal blood circulation problem, history of or
  • Intestinal obstruction (bowel blockage), history of or
  • Intestinal perforation (holes in bowel), history of or
  • Ischemic colitis (poor blood flow to bowel), history of or
  • Liver problems, severe or
  • Thrombophlebitis (inflamed blood vessel caused by blood clot), history of or
  • Toxic megacolon (very enlarged bowel), history of—Should not use in patients with these conditions.
  • Liver problems, mild or moderate—Use with caution. May have an increased risk of serious side effects.

Proper Use

Read the Medication Guide before starting alosetron for the first time and each time you refill your alosetron prescription.

Your doctor will ask you to sign a Patient-Physician Agreement after you have read the Medication Guide for the first time. Signing the agreement means that you understand the risks and benefits of alosetron therapy and that you have read and understand the Medication Guide.

Your doctor will tell you how much of this medicine to use and how often. Do not start taking alosetron if you are constipated. Do not use more medicine or use it more often than your doctor tells you to.

This medicine may be taken with or without food.


The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For irritable bowel syndrome (IBS):
      • Adults—At first, 0.5 milligram (mg) twice a day for 4 weeks. Your doctor may increase your dose to 1 mg twice a day for another 4 weeks.
      • Children—Use and dose must be determined by your doctor.

Missed Dose

If you miss a dose of this medicine, skip the missed dose and go back to your regular dosing schedule. Do not double doses.


Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Keep out of the reach of children.

Do not keep outdated medicine or medicine no longer needed.

Ask your healthcare professional how you should dispose of any medicine you do not use.


It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly and to decide if you should continue to take it.

Stop taking alosetron and check with your doctor right away if you become constipated or have symptoms of poor blood flow to your bowels (ischemic colitis). Some symptoms of poor blood flow are: new or worsening abdominal pain, bloody diarrhea, or blood in the stool.

Do not start taking alosetron again unless your doctor tells you to do so.

Do not take this medicine if you are also using fluvoxamine (Luvox®).

Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

  1. Constipation


  1. Bloody diarrhea
  2. new or worsening stomach pain or discomfort
  3. rectal bleeding

Incidence not known

  1. Abdominal or stomach pain, cramping, or burning
  2. black, tarry stools
  3. diarrhea
  4. fever
  5. heartburn
  6. indigestion
  7. nausea
  8. vomiting with or without blood or material that looks like coffee grounds

Get emergency help immediately if any of the following symptoms of overdose occur:

Symptoms of overdose

  1. Clumsiness, unsteadiness, trembling, or other problems with muscle control or coordination
  2. convulsions (seizures)
  3. difficulty breathing
  4. shakiness and unsteady walk
  5. withdrawn or socially detached behavior

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

  1. Bleeding after bowel movement
  2. full or bloated feeling
  3. pressure in the stomach
  4. swelling of abdominal or stomach area
  5. uncomfortable swelling around rectal area

Incidence not known

  1. Headache
  2. skin rash

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.