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Alosetron Dosage

Medically reviewed by Last updated on May 1, 2023.

Applies to the following strengths: 0.5 mg; 1 mg

Usual Adult Dose for Irritable Bowel Syndrome

Initial dose: 0.5 mg orally twice a day
Maintenance dose: 0.5 mg orally once or twice a day; may be increased up to 1 mg orally twice a day after 4 weeks of treatment.
Maximum dose: 2 mg/day

Comment: Due to the serious gastrointestinal adverse reactions associated with this drug, treatment should be restricted to female patients for whom the benefit-to-risk balance is most favorable.

Use: Women with severe diarrhea-predominant irritable bowel syndrome (IBS) who have chronic IBS symptoms (generally lasting 6 months or longer), had anatomic or biochemical abnormalities of the gastrointestinal tract excluded, and have not responded adequately to conventional therapy

Renal Dose Adjustments

No adjustment recommended.

Liver Dose Adjustments

Mild or moderate liver dysfunction (Child-Pugh score 9 or less): Use with caution.
Severe liver dysfunction (Child-Pugh score greater than 9): Contraindicated.

Dose Adjustments

Elderly or debilitated, and/or patients taking additional drugs that decrease gastrointestinal motility: Appropriate caution and follow-up should be considered.

Reduce frequency of dose to 0.5 mg orally once a day if constipation occurs with initial dose level; immediately discontinue if constipation recurs at this lower dose.

After 4 weeks of treatment: May increase dose up to 1 mg orally twice a day if current dosage well tolerated but IBS symptoms not adequately controlled; discontinue if IBS symptoms not controlled after 4 weeks of treatment at 1 mg orally twice a day.

Signs/symptoms of ischemic colitis or constipation: Discontinue treatment immediately; treatment should not be restarted in patients who develop ischemic colitis.


US REMS: The US FDA requires a Risk Evaluation and Mitigation Strategy (REMS) for this drug. It includes elements to assure safe use. For additional information:


  • Infrequent but serious gastrointestinal adverse reactions have been reported with the use of this drug. These events, including ischemic colitis and serious complications of constipations, have resulted in hospitalization and, rarely, blood transfusion, surgery, and death.
  • This drug is indicated only for women with severe diarrhea-predominant irritable bowel syndrome (IBS) who have not responded adequately to conventional therapy.
  • This drug should be discontinued immediately in patients who develop constipation or symptoms of ischemic colitis. Patients should immediately report constipation of symptoms of ischemic colitis to their prescriber. This drug should not be resumed in patients who develop ischemic colitis. Patients who have constipation should immediately contact their prescriber if the constipation does not resolve after this drug is discontinued. Patients with resolved constipation should resume this drug only on the advice of their treating prescriber.

Safety and efficacy have not been established in patients younger than 18 years. Use is not recommended in the pediatric population based upon the serious complications or constipation and ischemic colitis in adults.

Consult WARNINGS section for additional precautions.


Data not available

Other Comments

Administration advice: Take with or without food.

Storage requirements: Protect from light and moisture.


  • To prescribe this drug, physicians must be enrolled in the REMS program. The Prescriber Enrollment Form can be found at
  • This drug may be dispensed only if the prescription has a sticker for the REMS program attached; no telephone, facsimile, or computerized prescriptions are permitted with this drug.
  • Inhibition of the metabolic elimination and reduced first pass of other drugs might occur with overdoses of this drug.
  • This drug is for women only; there has not been enough testing done to confirm that this drug works in men and children under age 18.

  • Gastrointestinal: Signs/symptoms of constipation, serious complications of constipation, and ischemic colitis

Patient advice:
  • Patients should be told to avoid drinking alcohol while taking this drug.
  • Patients should be advised to immediately report signs/symptoms of constipation and/or ischemic colitis.
  • Advise patients to speak to their health care provider if they are pregnant, intend to become pregnant, or are breastfeeding.
  • Patients should be instructed to read the medication guide prior to starting treatment and each time they refill their prescription.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.