What is Alosetron used for?
Last updated September 7, 2026.
**Alosetron is a prescription medicine used to treat severe diarrhea-predominant irritable bowel syndrome (IBS-D) in women whose symptoms have not improved with other treatments.** It works on serotonin 5-HT3 receptors in the bowel, slowing stool transit so urgency, cramping, and loose stools ease up. Approval is narrow: it is meant for women with severe, chronic IBS-D lasting six months or longer, and it is not approved for men or for IBS with constipation. Because alosetron can cause serious constipation and ischemic colitis, it is prescribed under an FDA safety program, and your prescriber will review the risks with you before you start. Doctors usually begin at the lowest dose and reassess after about four weeks. Track your stool pattern and any abdominal pain each week so you and your clinician can tell whether it is helping.
What to do
- Confirm the diagnosis first: Alosetron is for confirmed severe IBS-D, so ask your clinician to rule out infection, celiac disease, and inflammatory bowel disease before starting.
- Start low: Most people begin at 0.5 mg twice daily, and your prescriber raises the dose only if symptoms are still uncontrolled after four weeks.
- Watch for two warning signs: Stop the drug and call your doctor if you become constipated or see blood in your stool, and do not restart it on your own.
- Skip it if you have bowel history: Tell your clinician about any past ischemic colitis, blocked or perforated bowel, diverticulitis, or Crohn disease, since these rule out alosetron.
- Review your other medicines: Fluvoxamine and some antibiotics such as ciprofloxacin raise alosetron levels, so share your full medication list including supplements.
- Set a stop point: If symptoms are no better after four weeks at the higher dose, alosetron is discontinued rather than continued indefinitely.
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