Classifications: serotonin 5-ht3 receptor antagonist;
Therapeutic:serotonin receptor antagonist
; gi antimotility
Pregnancy Category: B


1 mg tablets


Potent and selective serotonin (5-HT3) receptor antagonist. Serotonin 5-HT3 receptors are extensively located on enteric neurons of the GI tract. Activation of these receptors affects amount of visceral pain experienced, transit time in the colon, and GI secretions.

Therapeutic Effect

Blockage of the serotonin 5-HT3 receptors by alosetron results in significant control of GI pain, and severe diarrhea related to irritable bowel syndrome.


Treatment of severe irritable bowel syndrome (IBS) in women whose predominant symptom is diarrhea and whose symptoms have lasted >6 mo and have failed to respond to conventional therapy.


Constipation, ischemic colitis, development of ischemic bowel symptoms such as sudden onset of rectal bleeding, bloody diarrhea, new or sudden worsening of abdominal pain; history of chronic or severe constipation, intestinal obstruction, toxic megacolon, GI adhesions, GI perforation, active diverticulitis, history of, or current Crohn's disease or ulcerative colitis; hypersensitivity to alosetron; thrombophlebitis, hypercoagulable state, inability to comply with Patient–Physician Agreement.

Cautious Use

Hepatic insufficiency, renal impairment; elderly; pregnancy (category B), lactation. Safety and efficacy in children are not established.

Route & Dosage

Irritable Bowel Syndrome
Adult: PO Start with 1 mg q.d. for 4 wk, may increase to 1 mg b.i.d. if tolerated


  • Ensure that the patient has signed the Patient–Physician Agreement prior to administering alosetron.
  • Do not give this drug if the patient has constipation.
  • Review the contraindications for this drug and ensure that the patient has none of the conditions for which the drug is contraindicated.
  • Store at 25° C (77° F).

Adverse Effects (≥1%)

Body as a Whole: Malaise, fatigue, cramps, pain. CNS: Anxiety. CV: Tachyarrhythmias. GI: Constipation, abdominal pain, nausea, distention, reflux, hemorrhoids, hyposalivation, dyspepsia, ischemic colitis. Skin: Sweating, urticaria. Urogenital: Urinary frequency.


Drug: Fluvoxamine increases alosetron serum level.


Absorption: Rapidly absorbed, average bioavailability of 50–60%. Peak: 1 h. Distribution: 82% protein bound. Metabolism: Extensively in liver by CYP2C9. Elimination: 73% in urine, 24% in feces. Half-Life: 1.5 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor for and report immediately signs of ischemic colitis such as new or worsening abdominal pain, bloody diarrhea, or blood in the stool.
  • Withhold drug and notify physician if patient has not had adequate control of IBS symptoms after 4 weeks of treatment with 1 mg twice a day.
  • Monitor carefully patients who have decreased GI motility (e.g., older adults, persons receiving other drugs which may decrease GI motility) as they may be at greater risk of serious complications of constipation.
  • Monitor carefully patients with any degree of hepatic insufficiency as they may be more susceptible to adverse drug effects.
  • Monitor periodically for cardiac arrhythmias, especially with preexisting cardiovascular disease.

Patient & Family Education

  • Read the Medication Guide before starting alosetron and each time you refill your prescription.
  • Do not start taking alosetron if you are constipated.
  • Discontinue alosetron immediately and contact your physician if you experience any of the following: constipation, new or worsening abdominal pain, bloody diarrhea, or blood in the stool.
  • Contact your physician immediately if constipation does not resolve after discontinuation of alosetron. Resume alosetron again only if constipation has resolved and your physician directs you to begin taking the medication again.
  • Stop taking alosetron and contact your physician if IBS symptoms are not adequately controlled after 4 wk of taking 1 tablet twice a day.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2023 Last Updated On: 01/19/2023 (0)
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