Alosetron
Alosetron hydrochloride is a potent and selective serotonin 5-HT<sub>3</sub> receptor antagonist indicated for the management of severe diarrhea-predominant irritable bowel syndrome (IBS-D) in women whose symptoms have not responded adequately to conventional therapies.[1][2] By antagonizing 5-HT<sub>3</sub> receptors in the enteric nervous system, alosetron modulates gastrointestinal motility, secretion, and sensation, thereby reducing diarrhea, urgency, and abdominal pain associated with IBS-D.[3][4] Initially approved by the U.S. Food and Drug Administration in February 2000 under the brand name Lotronex, alosetron was voluntarily withdrawn from the market in November 2000 following reports of serious, potentially life-threatening gastrointestinal adverse events, including ischemic colitis and severe constipation leading to complications such as perforation and obstruction.[5][6] In response to patient advocacy and evidence of clinical benefits outweighing risks under strict prescribing conditions, the FDA permitted its reintroduction in June 2002 with a restricted distribution program emphasizing prescriber education, patient informed consent, and immediate discontinuation protocols for adverse symptoms; this program was later converted to a less stringent Risk Evaluation and Mitigation Strategy (REMS) before its removal in 2023.[5][3][7] Despite its efficacy in alleviating refractory IBS-D symptoms, alosetron's use remains limited to specialist oversight due to the black-box warnings for ischemic colitis and constipation-related risks, highlighting the trade-offs in its therapeutic profile.[8]