This page shows what was measured, who it was measured in, and what that does not settle.
What Alosetron does in the body
A tablet for severe diarrhoea-predominant irritable bowel syndrome in women, prescribed only under a special programme
The gut uses serotonin to drive movement, secretion and the sensation of pain. Alosetron blocks one particular serotonin receptor on gut nerves, so transit slows, less fluid is secreted and the gut becomes less sensitive to stretch — which is exactly what someone with severe diarrhoea and cramping needs. The same slowing can go too far, producing severe constipation, and in rare cases the blood supply to a segment of colon becomes inadequate.
What happened in people
Global symptom improvement relative risk 1.60 (95% CI 1.44 to 1.76) across 4,170 patients in eight trials
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
The limit that matters most
That the ischaemic colitis is caused by the constipation; serious constipation complications were not significantly increased while ischaemic colitis was
Where it acts
Enteric nervous system; 5-HT3 receptors on intrinsic and extrinsic afferent neurons of the gastrointestinal tract
Kind of result
Symptoms and quality of life
Supervision
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · 2F5R1A46YW · read 2026-08-29
Its recorded molecular formula is C17H18N4O•HCl, weighing 330.81 g/mol.
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
Where each sentence above came from
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 111 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
Randomisation
Randomisation means chance decides who gets which treatment.
A picture of it, and where the picture fails
It is like a coin toss deciding the groups.
Where that stops being true. A coin toss is fair once. Fairness here comes from doing it for everyone.
What people get wrong. It is thought to make groups identical. It makes them similar on average, including on things nobody measured.
Allocation of participants to arms by a chance process, so that unmeasured factors are balanced in expectation.
Absolute difference
An absolute difference is how many more people in a hundred were affected.
A picture of it, and where the picture fails
It is like counting heads in two rooms of a hundred.
Where that stops being true. Heads are easy to count. Study results carry a margin of error too.
What people get wrong. It is confused with a percentage change, which can look far larger.
The arithmetic difference in event rates between arms.
Confidence interval
A confidence interval is the range the true answer is likely to sit in.
A picture of it, and where the picture fails
It is like a weather forecast giving a range rather than one number.
Where that stops being true. A forecast range covers tomorrow. This one covers what the study could resolve.
What people get wrong. The middle number is read as the answer. A range crossing zero means no change is still possible.
An interval estimate that would contain the true parameter in a stated proportion of repeated studies.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Global improvement in irritable bowel syndrome symptoms, and adequate relief of pain and discomfort
✓ The study showed what it set out to show
Who was studied
Meta-analysis of eight randomised placebo-controlled trials of alosetron
How many people
4170
Study design
Meta-analysis of 12-week multicentre randomised placebo-controlled trials
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
Global improvement relative risk 1.60 (95% CI 1.44 to 1.76), P < 0.001; adequate relief of pain and discomfort 1.31 (1.20 to 1.43), P < 0.001; women 1.34 (1.21 to 1.48), men 1.23 (1.02 to 1.47)
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. The pooled population was 80 per cent female with only 2.6 per cent constipation-predominant disease, so the male and constipation-predominant estimates rest on small subsets. Tolerability differed from placebo, relative risk 1.19 (1.07 to 1.31).
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, 0.5 mg twice daily with cautious escalation to 1 mg twice daily
Interval reported. 95% CI 1
Written into the record, not signed off as a reviewed claim.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
PubChem CID 2099 — alosetron structure, formula and molecular weight (https://pubchem.ncbi.nlm.nih.gov/compound/2099) · a recorded source, not a stored snapshot
Adjudicated incidence of ischaemic colitis and serious complications of constipation in alosetron users, in trials and in post-marketing surveillance
✓ The study showed what it set out to show
Who was studied
Blinded expert adjudication of ischaemic colitis and constipation complications
How many people
19
Study design
Systematic review with blinded case adjudication of trial and post-marketing reports
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Trials: ischaemic colitis 0.15 per cent versus 0.0 per cent, P = 0.03; no significant difference in serious complications of constipation. Post-marketing: 1.1 ischaemic colitis and 0.66 serious constipation complications per 1,000 patient-years
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Post-marketing rates depend on an exposure denominator derived from the restricted prescribing programme, and on the adjudication panel's exclusion criteria for cases judged inconsistent or not drug-associated.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, 0.5 mg twice daily with cautious escalation to 1 mg twice daily
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
PubChem CID 2099 — alosetron structure, formula and molecular weight (https://pubchem.ncbi.nlm.nih.gov/compound/2099) · a recorded source, not a stored snapshot
What we know
RNAWiki holds 2 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Alosetron
What a person takes: Oral tablet, 0.5 mg twice daily with cautious escalation to 1 mg twice daily.
The measurement behind this step
Oral alosetron hydrochloride, started at the lowest dose and escalated only after four weeks if symptoms are inadequately controlled and constipation has not occurred. Extensively metabolised by CYP1A2, making fluvoxamine a contraindication and requiring caution with other CYP1A2 inhibitors.
Getting in
An oral tablet, started at the lowest dose
Taken by mouth, beginning at a low dose and increased only if symptoms are not controlled and constipation has not developed.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Oral alosetron hydrochloride, initiated at 0.5 mg twice daily with escalation to 1 mg twice daily only after four weeks if tolerated. Extensively metabolised by CYP1A2, so fluvoxamine is contraindicated and ciprofloxacin requires caution.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
Reaching the cell
Reaches the nerve networks of the gut wall
It reaches the nerve cells embedded in the wall of the intestine and the sensory fibres running from the gut to the spinal cord.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Distributes to enteric neurons of the myenteric and submucosal plexuses and to extrinsic vagal and spinal afferent terminals, where 5-HT3 receptors are expressed.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
What it acts on
Blocks the 5-HT3 ion channel
It plugs a serotonin-operated channel on those nerves, so the serotonin the gut releases can no longer excite them.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Selective antagonism at the 5-HT3 receptor, a ligand-gated cation channel. Blocking it prevents serotonin-evoked depolarisation of enteric and afferent neurons, rather than modulating a second-messenger cascade.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
The change it makes
Transit slows, secretion falls, sensation dulls
The gut moves contents more slowly, secretes less fluid, and reports less discomfort from stretching — all three at once.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Reduced excitatory 5-HT3 signalling slows colonic transit, reduces intestinal secretion and raises the threshold for visceral afferent firing on distension. The three effects are inseparable properties of the same blockade, which is why constipation is not a side effect but the same effect taken further.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
What that does for a person
Symptom relief in most; ischaemic colitis in about one per thousand patient-years
Global symptoms improved in substantially more patients than on placebo. Ischaemic colitis occurred in roughly one patient per thousand treated for a year, and in the trials every case resolved.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Measured: relative risk 1.60 (95% CI 1.44 to 1.76) for global symptom improvement across 4,170 patients. Measured: ischaemic colitis 0.15 per cent versus 0.0 per cent in pooled trials (P = 0.03), post-adjudication rate 1.1 per 1,000 patient-years, all 19 trial cases reversible without long-term sequelae.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
Women with severe diarrhoea-predominant irritable bowel syndrome who have failed conventional therapy, prescribed by clinicians enrolled in the programme. It is not indicated in men or in constipation-predominant disease.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What the label states about particular groups
On pediatric, the label states: “Safety and effectiveness in pediatric patients have not been established.”
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
On older people, the label states: “In some studies in healthy men or women, plasma concentrations were elevated by approximately 40% in individuals 65 years and older compared to young adults [see Warnings and Precautions (5.1) ] .”
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary The available data with alosetron hydrochloride use in pregnant women are insufficient to draw conclusions about any drug-associated risks for major birth defects, miscarriage, or adverse maternal or fetal outcomes.”
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary There are no data regarding the presence of alosetron in human milk, the effects on the breastfed infant, or the effects on milk production.”
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
On people with reduced liver function, the label states: “Due to the extensive hepatic metabolism of alosetron, increased exposure to alosetron and/or its metabolites is likely to occur in patients with hepatic impairment.”
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
On people with reduced kidney function, the label states: “(creatinine clearance 4 mL/min to 56 mL/min) has no effect on the renal elimination of alosetron due to the minor contribution of this pathway to elimination.”
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
Where the result stopped carrying
Approved February 2000 and voluntarily withdrawn in November 2000, nine months later
The original indication covered irritable bowel syndrome in women broadly; the reintroduced one covers severe diarrhoea-predominant disease after conventional therapy has failed
The mechanism of the ischaemic colitis remains unresolved between a direct vascular effect and a consequence of slowed transit
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Prescription only
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Oral tablet, 0.5 mg twice daily with cautious escalation to 1 mg twice daily
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Suppression classes recorded: S6.
No source is stored against this line.
What is in the pack
Oral alosetron hydrochloride, started at the lowest dose and escalated only after four weeks if symptoms are inadequately controlled and constipation has not occurred. Extensively metabolised by CYP1A2, making fluvoxamine a contraindication and requiring caution with other CYP1A2 inhibitors.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold and what that means for what is in the pack.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Constipation is the commonest adverse effect and is the same pharmacology as the therapeutic action taken further. The serious harms are ischaemic colitis — 0.15 per cent against 0.0 per cent on placebo in pooled trials, post-adjudication rate 1.1 per 1,000 patient-years, with all 19 trial cases reversible without long-term sequelae — and serious complications of constipation at 0.66 per 1,000 patient-years, which were not significantly increased over placebo in the trials. The drug is contraindicated in constipation, ischaemic colitis, Crohn's disease, ulcerative colitis, diverticulitis, adhesions and strictures, and must be stopped immediately if constipation or rectal bleeding occurs. Prescribing is restricted to enrolled clinicians.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Drugs@FDA: LOTRONEX (alosetron hydrochloride), NDA 021107 — Prescription (https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&Ap… · a recorded source, not a stored snapshot
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Oral tablet, 0.5 mg twice daily with cautious escalation to 1 mg twice daily
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
Extensively metabolised by CYP1A2, making fluvoxamine a contraindication and requiring caution with other CYP1A2 inhibitors.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
What is recorded as being sold
18 products list this as an active ingredient in the United States drug directory. 18 of them contain it and nothing else.
FDA National Drug Code directory · 73190-035 · read 2026-08-29
They are sold as powder, tablet and tablet, film coated, taken oral.
FDA National Drug Code directory · 73190-035 · read 2026-08-29
The regulator's established pharmacologic class for it is serotonin 3 receptor antagonists [moa] and serotonin-3 receptor antagonist [epc].
FDA National Drug Code directory · 73190-035 · read 2026-08-29
9 published labels name it as an active ingredient. 9 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-29
Alosetron Hydrochloride is oral at 3 DOSAGE FORMS AND STRENGTHS 0.5 mg and 1 mg tablets Alosetron tablets USP, 0.5 mg (0.562 mg alosetron hydrochloride, USP equivalent to 0.5 mg alosetron), are white, oval shaped, film coated tablets debossed with “AN248…, recorded as fda label in effect 2025-09-09 in the United States.
US prescribing information · 3ac203a2-4c55-deac-e063-6394a90aa165 · read 2026-08-30
Recorded price in US: 1.949–3.61824 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 8 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Alosetron studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That the ischaemic colitis is caused by the constipation; serious constipation complications were not significantly increased while ischaemic colitis was
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That the women-only indication reflects absence of efficacy in men — the pooled male estimate is 1.23 (1.02 to 1.47) and significant
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That spontaneous reports alone could have supported a rate; the denominator comes from the restricted prescribing programme
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
How much did people take in the studies?
The sources RNAWiki checked hold nothing for this field.
Why it matters. A result belongs to an amount. Without the amount the result floats free.
What would answer it
A stored source that records it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Alosetron are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
Ischaemic colitis in 0.15 per cent against 0.0 per cent on placebo
In plain words
In pooled trials, ischaemic colitis occurred in about 1.5 patients per thousand on alosetron and in none on placebo. Every one of the 19 cases resolved without lasting damage.
What was measured
Adjudicated incidence of ischaemic colitis and serious complications of constipation, alosetron versus placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A blinded expert adjudication reviewed clinical trial report forms and FDA MedWatch forms for every reported case of ischaemic colitis or serious complication of constipation, with the panel unaware of treatment assignment, rating diagnostic accuracy and likelihood of medication association against pre-specified criteria; cases inconsistent with the reported diagnosis or not possibly drug-associated were excluded from the incidence calculation. Pooled trial data showed ischaemic colitis in 0.15 per cent on alosetron against 0.0 per cent on placebo (P = 0.03), with no significant difference in serious complications of constipation. All 19 alosetron-treated patients with ischaemic colitis had reversible colitis without long-term sequelae.
Written into the record, not signed off as a reviewed claim
1.1 ischaemic colitis cases per 1,000 patient-years after adjudication
In plain words
From post-marketing data, about one patient in a thousand treated for a year developed ischaemic colitis, and about two-thirds of one in a thousand had a serious complication of constipation.
What was measured
Post-adjudication rate of ischaemic colitis and serious complications of constipation per 1,000 patient-years
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Post-marketing surveillance data, subjected to the same blinded adjudication, gave a post-adjudication rate of 1.1 cases of ischaemic colitis per 1,000 patient-years of alosetron use and 0.66 serious complications of constipation per 1,000 patient-years. The authors conclude that the incidence of both is very low and rarely associated with long-term sequelae or serious morbidity. This is what a restricted-access programme buys: an exposure denominator that spontaneous reporting cannot supply, so a numerator of case reports becomes a rate that a patient and a clinician can weigh against a symptom burden.
Written into the record, not signed off as a reviewed claim
Relative risk 1.60 for global symptom improvement across 4,170 patients
In plain words
Pooling eight trials, patients on alosetron were about 60 per cent more likely to report global improvement and about 30 per cent more likely to get adequate relief of pain.
What was measured
Pooled relative risk for global symptom improvement and for adequate relief of pain and discomfort
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A meta-analysis of eight multicentre randomised placebo-controlled 12-week trials including 4,170 patients with irritable bowel syndrome (80 per cent female, all meeting Rome criteria, only 2.6 per cent constipation-predominant) found alosetron significantly more effective than placebo for global improvement in symptoms across the three trials reporting it, relative risk 1.60 (95% CI 1.44 to 1.76, P < 0.001). Across the six trials reporting adequate relief of pain and discomfort the relative risk was 1.31 (95% CI 1.20 to 1.43, P < 0.001), and by sex 1.34 (1.21 to 1.48) in women and 1.23 (1.02 to 1.47) in men. Tolerability differed from placebo, relative risk 1.19 (1.07 to 1.31, P < 0.001).
Written into the record, not signed off as a reviewed claim
Nine months on the market, then eighteen months off, then back with conditions
In plain words
Approved February 2000, withdrawn November 2000, returned June 2002 with prescribing restricted to enrolled clinicians and a narrow patient group.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Alosetron was approved in February 2000 for irritable bowel syndrome in women, voluntarily withdrawn in November 2000 after reports of ischaemic colitis and serious complications of constipation, and reintroduced in 2002 under a restricted prescribing programme requiring prescriber enrolment, a patient-physician agreement and a narrowed indication: severe diarrhoea-predominant disease in women who have failed conventional therapy. Drugs@FDA records NDA 021107 for LOTRONEX in Prescription marketing status, with several generic applications also approved. What changed between 2000 and 2002 was not the drug or the risk but the size and definition of the exposed population, and the existence of a system that counts it.
Written into the record, not signed off as a reviewed claim
Whether the ischaemia is a vascular effect or a constipation effect is unresolved
In plain words
Nobody has established whether alosetron restricts blood flow to the colon directly, or whether the severe constipation it causes is what starves the tissue.
What was measured
That alosetron-associated ischaemic colitis is caused by the constipation the drug produces
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Two mechanisms are compatible with the data. Alosetron slows colonic transit, and severe constipation can raise intraluminal pressure enough to compromise mucosal perfusion — which would make ischaemic colitis a downstream consequence of the intended pharmacology rather than a separate action. Alternatively, 5-HT3 receptors are present on enteric neurons regulating vasomotor tone, so a direct effect on splanchnic perfusion is possible. The adjudicated analysis found ischaemic colitis significantly increased while serious complications of constipation were not significantly different between arms, which sits awkwardly with a purely constipation-mediated account. The two are not distinguished by the clinical data, and the distinction matters for whether the risk is dose-limitable.
Written into the record, not signed off as a reviewed claim
It works in men too, and the label does not cover them
In plain words
The pooled trials show a significant benefit in men as well as women. The indication is restricted to women, which is a risk decision rather than an efficacy finding.
What was measured
That the women-only indication reflects a lack of efficacy in men
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The meta-analysis reported adequate relief of pain and discomfort in both sexes: relative risk 1.34 (95% CI 1.21 to 1.48) in women and 1.23 (1.02 to 1.47) in men, both significant. The trials were 80 per cent female, so the male estimate is less precise, but it is not null. The restriction of the indication to women therefore reflects the composition of the safety data and the population in which the benefit-risk case was made, not a demonstrated absence of efficacy in men. Recording it as "alosetron does not work in men" would misstate the evidence; recording it as "the benefit-risk case was only made in women" is accurate.
Written into the record, not signed off as a reviewed claim
Blinded re-adjudication cut the case count before any rate was computed
In plain words
An expert panel that did not know who was on the drug reviewed each reported case and discarded those that were not really ischaemic colitis or not plausibly drug-related.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The adjudication panel comprised experts in epidemiology and functional bowel disorders, reviewed the primary trial report forms and MedWatch forms for each case, was blinded to whether the patient received alosetron or placebo, and applied pre-specified criteria to rate both diagnostic accuracy and the plausibility of a drug association. Cases inconsistent with the reported diagnosis or not possibly drug-associated were removed before the incidence rates were computed. That procedure is what separates the resulting figure — 1.1 per 1,000 patient-years — from a raw count of spontaneous reports. It is the same instrument that reversed the tegaserod decision on the same page of this file, applied here in the same direction rather than the opposite one.
This order is fixed in code and does not count clicks or time on the page.
What is not here
7 questions this page could not answer
These sections were prepared and left out because there was nothing to put in them. They are listed rather than hidden, so the gaps in this record are visible.
What was measured, goal by goal — found nothing in the sources checked.
How close this is to real life — found nothing in the sources checked.
Felt, measured, or meaningful — found nothing in the sources checked.
How long anything takes — found nothing in the sources checked.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
The record as stored
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
A 5-HT3 antagonist withdrawn nine months after approval over ischaemic colitis and complications of constipation, and returned in 2002 under restricted prescribing once the harms were quantified — a post-adjudication rate of 1.1 cases of ischaemic colitis per 1,000 patient-years, all 19 trial cases reversible without long-term sequelae, against a relative risk of 1.60 for global symptom improvement.
Recorded evidence blocks (8)
Q2
On the Alosetron label: indicated for what?
"LOTRONEX is indicated only for women with severe diarrhea-predominant irritable bowel syndrome (IBS) who have: chronic IBS symptoms (generally lasting 6 months or longer), had anatomic or biochemical abnormalities of the gastrointestinal tract excluded, and not responded adequately to conventional therapy.…": indications and usage on Alosetron's label. DailyMed label · 35cbb9d5-639b-207a-e054-00144ff88e88 · 2026-06-30
Q3
3 registered trials of Alosetron — at which phases?
1.5 hours; The terminal elimination half-life of alosetron is approximately 1.5 hours (plasma clearance is approximately 600 mL/min).
tmaxpharmacokinetics
1 hour; Following oral administration of a 1 mg alosetron dose to young men, a peak plasma concentration of approximately 5 ng/mL occurred at 1 hour.
bioavailabilitypharmacokinetics
50 %; Absorption: Alosetron was rapidly absorbed after oral administration with a mean absolute bioavailability of approximately 50% to 60% (approximate range, 30% to >90%).
metabolismpharmacokinetics
Metabolism and Elimination: Plasma concentrations of alosetron increase proportionately with increasing single oral doses up to 8 mg and more than proportionately at a single oral dose of 16 mg.
recorded 2026-06-30 · last checked 2026-09-04
Q5
Which 2 trials of Alosetron posted no result?
Posted no result
2 of 2 completed trials
Registrations
NCT00067561 and NCT00067457
Completion dates
oldest 2005-01; newest 2005-12
Show the evidence
Trial
NCT00067561
2005-01
NCT00067457
2005-12
Q6
At the median, Alosetron's trials enrolled 700 people — anything larger?
Median enrolment
700
Largest enrolment
702
Registered trials counted
3
Q7
What do 19 spontaneous reports say about Alosetron — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Alosetron appears in spontaneous reports to regulators. Across the 8 most-reported reaction terms, 19 reaction mentions were counted: nausea 4; abdominal pain 3; colitis ischaemic 3; constipation 3. FAERS via Open Targets · CHEMBL1110 · 2026-06-24
Show the evidence
nausea
4
abdominal pain
3
colitis ischaemic
3
constipation
3
haemorrhoids
2
intestinal obstruction
2
2 more recorded rows
faecal occult blood positive
1
mean platelet volume decreased
1
recorded 2026-06-24 · last checked 2026-09-04
Q8
Which 8 reactions does Alosetron's label not list?
In vivo data suggest that alosetron is primarily metabolized by cytochrome P450 (CYP) 1A2, with minor contributions from CYP3A4 and CYP2C9.
drug_interactions
CYP1A2 inhibitors: Avoid concomitant uses because of increased exposure and half-life of alosetron.
drug_interactions
( 4.3 , 7.1 ) CYP3A4 inhibitors: Use with caution in combination due to increased exposure of alosetron.
drug_interactions
( 7.2 ) 7.1 CYP1A2 Inhibitors Fluvoxamine is a known strong inhibitor of CYP1A2 and also inhibits CYP3A4, CYP2C9, and CYP2C19.
drug_interactions
Concomitant administration of alosetron and moderate CYP1A2 inhibitors, including quinolone antibiotics and cimetidine, has not been evaluated, but should be avoided unless clinically necessary because of similar potential drug interactions.
drug_interactions
7.2 CYP3A4 Inhibitors Ketoconazole is a known strong inhibitor of CYP3A4.
2 more recorded rows
Interaction statementdrug_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.
Interaction statementdrug_interactions
In an in vivo metabolic probe study, alosetron did not inhibit CYP2E1 but did produce 30% inhibition of both CYP1A2 and N-acetyltransferase.
ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 5 source rows
✓ no critical contamination: no quarantine open
✓ canonical metadata passed: slug and display name present
✓ no raw internal fields: enforced by the copy-contract test over the rendered page
This is a record of evidence. It is not medical advice, and it does not say this substance suits you. Nothing here says any substance on RNAWiki is appropriate for a child.