Drug information of Alosetron


Drug group:

Alosetron is a 5-HT3 antagonist used only for the management of severe diarrhoea-predominant irritable bowel syndrome (IBS) in women. Alosetron has an antagonist action on the 5-HT3 receptors and thus may modulate serotonin-sensitive gastrointestinal (GI) processes.

Mechanism of effect

Alosetron is a potent and selective 5-HT3 receptor antagonist. 5-HT3 receptors are nonselective cation channels that are extensively distributed on enteric neurons in the human gastrointestinal tract, as well as other peripheral and central locations.

Activation of these channels and the resulting neuronal depolarization affect the regulation of visceral pain, colonic transit and gastrointestinal secretions, processes that relate to the pathophysiology of irritable bowel syndrome (IBS). 5-HT3 receptor antagonists such as alosetron inhibit activation of non-selective cation channels which results in the modulation of serotonin-sensitive GI motor and sensory processes.


Alosetron is a potent and selective antagonist of the serotonin 5-HT3 receptor type. Activation of these receptors and the resulting neuronal depolarization affects the regulation of visceral pain, colonic transit, and GI secretions processes that are related to IBS. By blocking these receptors, alosetron is able to effectively control IBS.


Half-life: 1.5 hr

Peak plasma time: 0.5-1.7 hr

Bioavailability: 50-60%, food decreases absorption

Protein bound: 82%

Vd: 65-95 L

Excretion: Urine (74%); feces (11%)

Metabolites: 6-hydroxyl metabolite, 6-O-glucuronide metabolite, bis-oxidized dicarbonyl metabolite, N-demethylated alosetron [all are inactive]


  • Extensively undergoes first-pass metabolism
  • Metabolized by Cytochrome (CYP) P450  and non-CYP mediated phase I metabolism Clearance
  • Renal: 94 mL/min
  • Total body: 1190 mL/min



Irritable Bowel Syndrome

Indicated only for women with severe diarrhea-predominant IBS who have: chronic IBS symptoms (generally lasting 6 months or longer), had anatomic or biochemical abnormalities of GI tract excluded, and not responded adequately to conventional therapy

Initial 0.5 mg PO q12hr for 4 weeks; if well tolerated, but inadequate control of IBS symptoms, increase up to 1 mg q12hr; discontinue if no improvement after 4 weeks


Not recommended


Infrequent but serious GI adverse reactions (eg, ischemic colitis, serious complications of constipation) reported; some have resulted in hospitalization and, rarely, blood transfusion, surgery, or death

Indicated only for women with severe diarrhea-predominant irritable bowel syndrome that has not responded adequately to conventional therapy

Discontinue immediately in patients who develop constipation or symptoms of ischemic colitis; do not resume in those who develop ischemic colitis

Discontinue if inadequate control after 4 weeks of q12hr dosing

Risk of complications from constipation higher in the elderly

Use with caution in breast-feeding women

Use caution in mild-to-moderate hepatic impairment

Points of recommendation

It may take 1 month to see the full effect.

Take with or without food.

Take alosetron at the same time of day.

Pregnancy level


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