ALOSETRON HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ALOSETRON HYDROCHLORIDE (ALOSETRON HYDROCHLORIDE).
Alosetron is a selective antagonist of the serotonin 5-HT3 receptor. By blocking 5-HT3 receptors in the gastrointestinal tract and central nervous system, it reduces visceral hypersensitivity, colonic motility, and intestinal secretions, thereby alleviating symptoms of diarrhea-predominant irritable bowel syndrome (IBS-D).
| Metabolism | Primarily metabolized by hepatic cytochrome P450 enzymes, mainly CYP2C9, CYP3A4, and CYP1A2; also undergoes N-demethylation via CYP1A2. |
| Excretion | Renal: ~73% (mostly as metabolites), Fecal: ~24%, Biliary: minor; <1% excreted unchanged in urine. |
| Half-life | Terminal half-life is approximately 1.5–2 hours in healthy volunteers; prolonged in hepatic impairment (up to 2.5 hours) but no significant accumulation with repeated dosing. |
| Protein binding | ~82% bound to plasma proteins, mainly to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Approximately 65 L (0.9 L/kg for a 70 kg adult); indicates extensive tissue distribution. |
| Bioavailability | Oral: ~50–60% (first-pass metabolism); absolute bioavailability is 50–60%. |
| Onset of Action | Oral: Reduction in colonic transit begins within 30–60 minutes; clinical effect on stool consistency and abdominal pain typically within 1–2 days. |
| Duration of Action | Duration of clinical effect: symptom relief persists for the dosing interval (twice daily); colonic transit slowing lasts up to 6–8 hours after a single oral dose. |
1 mg orally twice daily for 4 weeks; if response is inadequate, increase to 1 mg twice daily for an additional 4 weeks.
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment. |
| Liver impairment | Contraindicated in patients with hepatic impairment; not recommended for use. |
| Pediatric use | Safety and efficacy not established; not recommended for use in pediatric patients. |
| Geriatric use | No specific dose adjustment recommended; monitor for adverse effects such as constipation and ischemic colitis. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ALOSETRON HYDROCHLORIDE (ALOSETRON HYDROCHLORIDE).
| Breastfeeding | Alosetron is excreted in rat milk at concentrations similar to maternal plasma; however, no data exist on its excretion in human breast milk. The M/P ratio is unknown. Due to the potential for serious adverse reactions in nursing infants, including gastrointestinal effects and possible hypersensitivity, breast-feeding is not recommended during alosetron therapy. A decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother. |
| Teratogenic Risk | Alosetron hydrochloride is contraindicated in pregnancy. There are no adequate and well-controlled studies in pregnant women. In animal studies, no evidence of teratogenicity was observed at doses up to 48 mg/kg/day in rats and 30 mg/kg/day in rabbits (approximately 200 and 240 times the recommended human dose, respectively). However, because animal reproduction studies are not always predictive of human response, and due to the drug's indication for IBS-D (irritable bowel syndrome with diarrhea) which is itself a contraindication for use in pregnancy, alosetron should not be used during any trimester unless absolutely necessary and only if the potential benefit justifies the potential risk to the fetus. |
■ FDA Black Box Warning
Serious gastrointestinal adverse events, including ischemic colitis and serious complications of constipation (such as obstruction, perforation, impaction, toxic megacolon, secondary ischemic colitis, and death), have been reported. Use only in women with severe IBS-D who have failed conventional therapy and meet the strict prescribing criteria.
| Serious Effects |
History of chronic or severe constipation; complications of constipation; history of ischemic colitis; impaired intestinal circulation; thrombophlebitis; increased risk of ischemic colitis; active diverticulitis; Crohn's disease; ulcerative colitis; bowel obstruction; stricture; toxic megacolon; gastrointestinal perforation; adhesions; and hypersensitivity to alosetron.
| Precautions | Risk of ischemic colitis and serious complications of constipation; discontinue immediately if constipation or rectal bleeding occurs. Use lowest effective dose for shortest duration. Not recommended for men or for patients with mild or moderate IBS-D. Monitor for signs of impaired intestinal function. |
| Food/Dietary |
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| Fetal Monitoring | If alosetron is used inadvertently during pregnancy, no specific monitoring for fetal effects is recommended beyond routine prenatal care. However, due to the risk of serious gastrointestinal adverse events (e.g., ischemic colitis, complications of constipation) in the mother, close monitoring for signs of colitis or severe constipation is warranted. Fetal heart rate monitoring may be considered if maternal complications arise that could compromise fetal well-being. |
| Fertility Effects | No adequate studies on the effects of alosetron on human fertility have been conducted. In animal studies, there were no adverse effects on fertility in rats at oral doses up to 48 mg/kg/day (approximately 200 times the recommended human dose). However, given the drug's serotonergic mechanism and its primary use in IBS-D, the impact on fertility in humans is unknown. Patients experiencing menstrual irregularities or other fertility issues should be evaluated for alternative causes. |
| Take this medication on an empty stomach (at least 1 hour before or 2 hours after a meal). Avoid grapefruit juice as it may increase alosetron levels. No other known food interactions. |
| Clinical Pearls | Alosetron is a 5-HT3 receptor antagonist indicated only for women with severe diarrhea-predominant irritable bowel syndrome (IBS-D) who have failed conventional therapy. Due to risk of ischemic colitis and serious complications of constipation, it is available only through a restricted prescribing program. Prescribe lowest effective dose (0.5 mg twice daily initially) and discontinue immediately if constipation or rectal bleeding occurs. Avoid in patients with history of chronic constipation, bowel obstruction, or ischemic colitis. |
| Patient Advice | Take exactly as prescribed; do not increase dose or frequency. · Stop the medication and contact your doctor immediately if you experience new or worsening constipation, rectal bleeding, or severe abdominal pain. · This medication is only for women with severe IBS-D that has not responded to other treatments. · You must enroll in the restricted access program; your doctor will provide details. · Do not take alosetron if you have a history of constipation, bowel obstruction, or colitis. · Store at room temperature away from moisture and heat. |