5-HT3 receptor antagonists
Alosetron is a selective 5-HT3receptor antagonist used for short-term treatment of women with irritable bowel syndrome (IBS) with severe diarrhea as the main symptom. This drug is available only through a restricted marketing program because of reported serious GI adverse effects. Only prescribers enrolled in the pre-scribing program for alosetron may write a prescription for it.
Alosetron is rapidly absorbed after oral administration and is me-tabolized by the cytochrome P450 pathway.
Alosetron is thought to block serotonin in the GI system, thereby reducing the abdominal cramping and discomfort, urgency, and di-arrhea commonly associated with IBS.
Alosetron is used for the short-term treatment of a woman with IBS whose primary symptom is diarrhea. The drug shouldn’t be taken if the patient is constipated and should be stopped if consti-pation develops.
Alosetron produces a 30% inhibition of N-acetyltransferase and CYP1A2. Although studies haven’t been done, the inhibition of N-acetyltransferase may have clinical significance when alosetronis given with such drugs as isoniazid, procainamide, and hydral-azine. Alosetron given with other drugs that decrease GI motility could cause constipation. (See Adverse reactions to alosetron.)