Prescription medication · 5-HT3 Antagonist (IBS-D)
alosetron
Also sold as Lotronex. Alosetron is used to treat severe diarrhea-predominant irritable bowel syndrome (IBS) in women.
Data updated 2026-05-15
- 73
- FDA reportsRarely reported
- 12
- InteractionsSeveral interactions
- $2.42
- Generic price (NADAC)
What the data shows
alosetron (Lotronex) is a prescription 5-HT3 Antagonist (IBS-D), among the least-reported drugs the FDA tracks (73 FDA reports), with 12 documented drug interactions.
Reporting volume reflects how widely a drug is used and studied, not how dangerous it is, a FAERS report documents a temporal association, never proof of cause.
alosetron (Lotronex) is a prescription 5-HT3 Antagonist (IBS-D). Alosetron is used to treat severe diarrhea-predominant irritable bowel syndrome (IBS) in women.
Alosetron (Lotronex) is a medicine for women with severe diarrhea-predominant irritable bowel syndrome (IBS). It helps to reduce diarrhea and stomach pain.
Verify with FDA → · CMS NADAC pricing →
Drug Pricing (NADAC)
Generic Price
$2.42/unit
Generic Available
Yes (3 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
Alosetron is used to treat severe diarrhea-predominant irritable bowel syndrome (IBS) in women.
Common side effects
Constipation, Abdominal discomfort and pain, Nausea
Key warnings
Alosetron can cause serious gut problems, like ischemic colitis (reduced blood flow to the bowel) and severe constipation.
The sections below are summarized in plain English from alosetron's FDA-approved prescribing information. They describe what the official label says, and are not personal medical advice.
How It Works
Alosetron blocks a substance called serotonin in your gut. Serotonin can speed up bowel movements. By blocking serotonin, alosetron slows down your bowel and reduces diarrhea.
How to Take It
Start with 0.5 mg twice a day. You can take it with or without food. After 4 weeks, if it's working well but not enough, your doctor may increase your dose to 1 mg twice a day. If you still have IBS symptoms after 4 weeks on the higher dose, stop taking alosetron.
This is a plain-language summary of alosetron's FDA labeling, not individualized dosing advice. Ask a pharmacist or prescriber before changing how you take this medication.
Pregnancy & Breastfeeding
It is not known if alosetron can harm your unborn baby. Talk to your doctor if you are pregnant or plan to become pregnant. It is also not known if alosetron passes into breast milk. Talk to your doctor about the best way to feed your baby if you take alosetron.
This is a plain-language summary of alosetron's FDA labeling, not individualized advice. Ask a pharmacist or prescriber about pregnancy or breastfeeding on this medication.
Missed Dose
If you miss a dose, skip that dose and take your next dose at the regular time. Do not take two doses at once.
This is a plain-language summary of alosetron's FDA labeling, not individualized advice. Ask a pharmacist or prescriber what to do about your specific missed dose.
Storage
Store alosetron tablets at room temperature (68-77°F). Keep them protected from light and moisture.
Side Effects (from patient reports)
Based on 73 FDA adverse event reports.
Most-reported reactions
Adverse reactions in FAERS for alosetron, by number of reports
- Diarrhea
Diarrhea
10 reports
- Feeling sick to your stomach
Feeling sick to your stomach
8 reports
- Stomach pain
Stomach pain
6 reports
- Death
Death
6 reports
- Having trouble passing stool
Having trouble passing stool
5 reports
- Feeling tired
Feeling tired
5 reports
- Pain
Pain
5 reports
- Weakness
Weakness
4 reports
- Condition getting worse
Condition getting worse
4 reports
- Sickness
Sickness
4 reports
What this shows Bars show how often each reaction was reported, not how likely it is to happen, a report records a temporal association, never proof that the drug caused it.
Reports over time
Adverse-event reports filed for alosetron each year to the FDA Adverse Event Reporting System (FAERS).
Year-to-year volume tracks usage, prescribing, and scrutiny, not a change in per-patient risk. Source: FDA FAERS.
Where alosetron sits
alosetron has more FDA adverse-event reports than 1% of the drugs FAERS tracks. A high position reflects how widely a drug is used and watched, not how dangerous it is.
Percentile across all drugs PlainMeds tracks by FAERS report volume. The dot is alosetron; the line is the median (50th percentile).
FDA Adverse Event Report Analysis
Detailed analysis of 73 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
73
Reports Mentioning Death
8
11.0% of reports — not proof of cause
Hospitalization Reports
18
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 2 | DIARRHOEA | 10 |
| 3 | NAUSEA | 8 |
| 5 | ABDOMINAL PAIN | 6 |
| 6 | DEATH | 6 |
| 7 | CONSTIPATION | 5 |
| 8 | FATIGUE | 5 |
| 9 | PAIN | 5 |
| 10 | ASTHENIA | 4 |
| 11 | CONDITION AGGRAVATED | 4 |
| 12 | ILLNESS | 4 |
| 13 | MUSCLE SPASMS | 4 |
| 15 | VOMITING | 4 |
| 16 | COLITIS ISCHAEMIC | 3 |
| 17 | COVID-19 | 3 |
| 18 | DECREASED APPETITE | 3 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
Alosetron can cause serious gut problems, like ischemic colitis (reduced blood flow to the bowel) and severe constipation. These problems can lead to hospitalization, surgery, or even death. Stop taking alosetron right away if you get constipated or have symptoms of ischemic colitis, like bloody diarrhea or bad stomach pain. Call your doctor immediately.
Known Drug Interactions
Coadministration of alosetron and strong CYP3A4 inhibitors such as clarithromycin, telithromycin, protease inhibitors, voriconazole, and itraconazole has not been evaluated but should be undertaken with caution because of similar potential drug interactions.
Mechanism: Clarithromycin blocks the enzymes that break down alosetron, which could lead to higher levels of alosetron in your body.
What to do: Use this combination with caution and tell your doctor if you notice any new side effects.
Coadministration of alosetron and strong CYP3A4 inhibitors such as clarithromycin, telithromycin, protease inhibitors, voriconazole, and itraconazole has not been evaluated but should be undertaken with caution because of similar potential drug interactions.
Mechanism: Itraconazole may block the liver enzymes that break down alosetron, which could lead to higher levels of the drug in your body.
What to do: Use this combination with caution and talk to your doctor about any new or worsening side effects.
Coadministration of alosetron and strong CYP3A4 inhibitors such as clarithromycin, telithromycin, protease inhibitors, voriconazole, and itraconazole has not been evaluated but should be undertaken with caution because of similar potential drug interactions.
Mechanism: Voriconazole can slow down how your body processes alosetron, potentially causing the medication to build up in your system.
What to do: Be careful when taking these drugs together and report any unusual symptoms to your healthcare provider.
Another study showed that alosetron had no clinically significant effect on plasma concentrations of the oral contraceptive agents ethinyl estradiol and levonorgestrel (CYP3A4 substrates).
Mechanism: Alosetron does not seem to change the amount of estradiol in your blood.
What to do: You can typically take these medications together without needing to change your dose.
Although not studied with alosetron, inhibition of N-acetyltransferase may have clinically relevant consequences for drugs such as isoniazid, procainamide, and hydralazine.
Mechanism: Alosetron may interfere with the way your body processes hydralazine, potentially leading to higher drug levels.
What to do: Talk to your doctor about monitoring your blood pressure and watching for any new symptoms.
This is a plain-language summary of interactions documented in FDA labeling, not individualized advice. Ask a pharmacist or prescriber before combining medications.
Common Questions
Can men take alosetron?
What should I do if I get constipated while taking alosetron?
Can I take alosetron if I have liver problems?
Can I take alosetron with other medicines?
How long does it take for alosetron to start working?
What are the symptoms of ischemic colitis?
What should I do if my constipation does not resolve after stopping alosetron?
Can I drive or operate machinery while taking alosetron?
What do the alosetron tablets look like?
How should I dispose of unused alosetron tablets?
What are the common side effects of alosetron?
Does alosetron interact with other medications?
What drug class is alosetron?
Is alosetron safe during pregnancy?
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What the FDA Data Shows for alosetron
The FDA label for alosetron (sold under brand names such as Lotronex) classifies it as a prescription-only medication in the 5-HT3 Antagonist (IBS-D) class. Alosetron is used to treat severe diarrhea-predominant irritable bowel syndrome (IBS) in women. Official labeling lists 4 commonly reported side effects, including Constipation, Abdominal discomfort and pain, Nausea.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 73 voluntary reports. The database also lists 12 documented drug interactions derived from FDA labeling, with the top-flagged interaction rated moderate severity. NADAC pricing from CMS shows a generic unit cost of $2.42.
Report counts do not establish causation, a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice, always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: October 1, 2025
Read our methodology - how this data is sourced, computed, and verified.
Data currency: FDA FAERS adverse-event reports through 2025, CMS NADAC acquisition-cost pricing effective December 2024, compiled and last refreshed May 2026. See our methodology for per-source dates and refresh cadence. Spot a figure that looks wrong? Report a correction.
All federal data sources used on this page
- FDA Orange Book - approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed - NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) - post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm - standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files - federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database - current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages