Alosetron

About Alosetron

Alosetron blocks serotonin 5-HT3 receptors in the gut, which slows bowel movement and eases pain and urgency. The label approves it only for women with severe diarrhea-predominant IBS: symptoms lasting six months or longer, with other bowel disease ruled out, and an inadequate response to conventional treatment. Severe means diarrhea plus frequent severe abdominal pain, frequent urgency or fecal incontinence, or restriction of daily activities. Its benefit in men has not been adequately shown, and it is not recommended for children. The starting dose is 0.5 mg twice a day. If constipation occurs, the drug is held until it resolves and may be restarted at 0.5 mg once a day; if constipation returns at that dose, it is stopped. After four weeks at a well-tolerated dose with symptoms still not controlled, the dose may be raised to 1 mg twice a day, and the drug is stopped if symptoms are still not controlled after four weeks at that dose.

The boxed warning covers infrequent but serious gastrointestinal reactions, including ischemic colitis and serious complications of constipation (obstruction, ileus, impaction, toxic megacolon and bowel ischemia), which have led to hospitalization and, rarely, blood transfusion, surgery or death. Alosetron is stopped immediately for constipation or for rectal bleeding, bloody diarrhea, or new or worse abdominal pain, and it is never restarted after ischemic colitis. It must not be started by anyone who is constipated, and it is contraindicated with a history of chronic or severe constipation or its complications, intestinal obstruction, stricture, toxic megacolon, perforation or adhesions, ischemic colitis or poor bowel circulation, thrombophlebitis or a clotting tendency, Crohn’s disease or ulcerative colitis, diverticulitis, severe liver impairment, or the antidepressant fluvoxamine. Constipation is the most common side effect, with abdominal discomfort and nausea next, and the risk of serious complications is higher in older or debilitated patients and with other medicines that slow the bowel.

For years alosetron was dispensed under a REMS with elements to assure safe use. In September 2023 the FDA determined that those elements were no longer necessary and that a REMS is no longer required for alosetron, though the boxed warning remains and the label still asks prescribers to counsel patients on the risks before the first prescription. A Medication Guide comes with every fill. Fluvoxamine, a strong CYP1A2 inhibitor, is contraindicated because it raised alosetron exposure several-fold; other CYP1A2 inhibitors such as cimetidine and quinolone antibiotics are avoided unless clinically needed, and ketoconazole and strong CYP3A4 inhibitors are used with caution. Human data in pregnancy are insufficient, and a breastfed infant would be watched for severe constipation. Alosetron is not a controlled substance.

Taking Alosetron

How to take it

Take it by mouth with or without food, at about the same times each day, usually twice a day. Read the Medication Guide that comes with each fill. Alosetron controls IBS but does not cure it, and symptoms may return within a week or two of stopping.

If you miss a dose

Skip the missed dose and take the next one at the regular time. Do not take a double dose.

Storage

In the original tightly closed container at room temperature, protected from light and moisture (not in the bathroom), out of reach of children.

Interactions to know about

Fluvoxamine is contraindicated. Cimetidine and quinolone antibiotics such as ciprofloxacin are avoided unless clinically necessary, and ketoconazole, clarithromycin, itraconazole, voriconazole and HIV protease inhibitors are used with caution. Other medicines that slow the bowel add to the constipation risk; tell the pharmacist about everything you take.

This summarizes the official prescribing information. Your prescriber’s and pharmacist’s instructions, and the leaflet that comes with your medicine, take priority.

Why the cash price for Alosetron differs from pharmacy to pharmacy

Alosetron is a low-volume specialty generic: it is approved for a narrow group of patients, few prescriptions are written, and not every pharmacy keeps it on the shelf, so one may quote from stock while another orders it in. Quotes also depend on whether the prescription is filled with the brand or a generic, and on which generic maker the pharmacy buys from.

The dose runs from one tablet a day to two a day, so the monthly count varies, and the brand and some generics come only in bottles of 30; the quote should match the exact strength and count written, since the 0.5 mg and 1 mg tablets are separate products.

Ways to pay less for Alosetron without insurance

• Ask the prescriber to write alosetron generically and allow substitution; the brand Lotronex costs far more than the generics.
• Ask the pharmacy to quote the exact strength and quantity on your prescription, since a 0.5 mg tablet once a day and a 1 mg tablet twice a day are very different monthly counts.
• Compare more than one pharmacy, and ask whether yours stocks alosetron or needs a day or two to order it.
• Once your dose is settled and well tolerated, ask the prescriber whether a ninety-day supply suits you.
• Upload the prescription to Script Unlock so licensed pharmacies can quote their cash price. You pay the pharmacy directly.

Questions to ask your pharmacist about Alosetron

1. 1.Which symptoms mean I should stop my alosetron right away and call my doctor?
2. 2.Do any of my medicines, such as fluvoxamine, cimetidine or an antibiotic, interact with my alosetron?
3. 3.If I become constipated and my doctor restarts me at a lower dose, do I need a new prescription for the other strength?
4. 4.Can my prescription be filled with a generic, and does the pharmacy keep it in stock?

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