Alosetron side effects: what 831 FDA adverse event reports show

Alosetron Hydrochloride · 13 reaction terms · 295 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Who reports

831 reports · 44% serious · 41 with death outcome · 90% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Alosetron tablets are 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.

FDA label, Indications and Usage

What it is

The active ingredient in alosetron tablets USP, is alosetron hydrochloride (HCl) USP, a potent and selective antagonist of the serotonin 5-HT 3 receptor type.

FDA label, Description section

Boxed warning

SERIOUS GASTROINTESTINAL ADVERSE REACTIONS Infrequent but serious gastrointestinal adverse reactions have been reported with the use of alosetron tablets. These events, including ischemic colitis and serious complications of constipation, have resulted in hospitalization, and rarely, blood transfusion, surgery, and death.

FDA label

How to read this page. FAERS is a spontaneous-reporting system: counts are not incidence rates and a signal is not proof of causation. Each reaction below is run through an automated screen — is the term in the FDA label (known), in the indications (the disease being treated), an administrative/coding term, or none of these (unlabeled)? That screen is mechanical text matching, not a causality assessment. The 30 hand-written Bradford Hill assessments are on the causality assessment page. Not medical advice.

Causality screen of the 12 strongest signals

Labeled — boxed warning 3Labeled adverse reaction 1Labeled (related wording) 2Likely indication confounding 2Reporting / coding artifact 1Not in label — unassessed 3

What the badges mean

Labeled — boxed warning The term (or its clinical synonym) appears in the FDA boxed warning: causality is regulator-recognised and considered serious.
Labeled adverse reaction The exact term appears in the label's warnings or adverse-reactions sections: a known, expected effect. The FAERS signal confirms the label rather than discovering anything.
Labeled (related wording) The label describes this effect under different wording (e.g. 'neutropenia' for 'neutrophil count decreased'). Treated as known.
Likely indication confounding The term appears in the label's indications: reports probably describe the disease being treated (or its progression), not a drug effect. Classic confounding by indication.
Reporting / coding artifact An administrative, monitoring or exposure term (product issue, off-label use, 'test normal', overdose...). Not a biological reaction; a high PRR here reflects how reports are coded.
Not in label — unassessed Not found in the label text, not an artifact pattern. This is a genuine candidate for a formal causality assessment (Bradford Hill / WHO-UMC); it has NOT had one here.

Strongest disproportionality signals

Flagged terms (PRR ≥ 2, χ² ≥ 4, n ≥ 10), ranked by PRR; infinite PRRs (no comparator reports) excluded. The EBGM column is a second, shrinkage-based estimate (MGPS) with its 5th percentile EB05 and the BCPNN IC025; a pair flagged by PRR alone is marked PRR-only and should be read as fragile. The strata column recomputes the PRR on serious reports only and flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 1 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.

Show: hide coding/lab/outcome terms hide indication terms unlabeled only hide PRR-only

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Diarrhoea haemorrhagic	10	26.9 14.5–49.9ROR 27.3 · χ² 224 / p 5e-51	25.6 EB05 14.6 · IC025 +2.5 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 38.2	no trial data cached
Irritable bowel syndrome	20	23.6 15.3–36.4ROR 24.2 · χ² 411 / p 1e-91	23.1 EB05 15.7 · IC025 +3.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 25.8	no trial data cached
Rectal haemorrhage	35	20.5 14.8–28.3ROR 21.3 · χ² 630 / p 3e-139	20.2 EB05 15.2 · IC025 +3.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 21.5 · 71% consumer	no trial data cached
Small intestinal obstruction	8	16.4 8.2–32.8ROR 16.6 · χ² 101 / p 4e-24	14.2 EB05 6.3 · IC025 +1.9 3/3 methods agree	Labeled (related wording) related wording	serious PRR 21.9	no trial data cached
Gastrointestinal pain	7	16.1 7.7–33.7ROR 16.2 · χ² 85 / p 2e-20	13.3 EB05 5.4 · IC025 +1.7 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 4.6	no trial data cached
Haemorrhoids	12	15.5 8.8–27.2ROR 15.7 · χ² 148 / p 2e-34	14.3 EB05 7.8 · IC025 +2.3 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 23.3	no trial data cached
Constipation	128	14.9 12.7–17.5ROR 17.4 · χ² 1,664 / p <1e-300	14.9 EB05 12.8 · IC025 +3.5 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 15.8 · 75% consumer	no trial data cached
Intestinal perforation	6	13.5 6.1–29.9ROR 13.6 · χ² 57 / p 2e-14	9.8 EB05 3.9 · IC025 +1.4 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 17.9	no trial data cached
Adverse event	43	11.8 8.8–15.7ROR 12.4 · χ² 414 / p 2e-92	11.4 EB05 8.7 · IC025 +2.9 3/3 methods agree	Reporting / coding artifact	serious PRR 4.1	no trial data cached
Hernia	8	10.5 5.3–20.9ROR 10.6 · χ² 59 / p 6e-15	7.9 EB05 3.9 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 9.7	no trial data cached
Anorexia	5	9.6 4.0–23.1ROR 9.7 · χ² 31 / p 2e-8	6.1 EB05 2.6 · IC025 +0.9 3/3 methods agree	Not in label — unassessed	serious PRR 10.1	no trial data cached
Pharmaceutical product complaint	10	9.6 5.2–17.7ROR 9.7 · χ² 68 / p 6e-17	7.5 EB05 4.1 · IC025 +1.7 3/3 methods agree	Not in label — unassessed	–	no trial data cached

Trial evidence (ClinicalTrials.gov)

Trial cross-check not yet run for this drug (ClinicalTrials.gov pull covers the 800 most-reported drugs first).

Most frequently reported reactions

By raw co-report count, regardless of disproportionality. Common terms here are often the illness itself or generic outcomes.

Reaction	Reports	PRR 95% CI · ROR · χ²/p	EBGM EB05 · IC025	Label screen	Serious-only & strata	Trial cross-check
Constipation	128	14.9 12.7–17.5ROR 17.4 · χ² 1,664 / p <1e-300	14.9 EB05 12.8 · IC025 +3.5 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 15.8 · 75% consumer	no trial data cached
Adverse event	43	11.8 8.8–15.7ROR 12.4 · χ² 414 / p 2e-92	11.4 EB05 8.7 · IC025 +2.9 3/3 methods agree	Reporting / coding artifact	serious PRR 4.1	no trial data cached
Rectal haemorrhage	35	20.5 14.8–28.3ROR 21.3 · χ² 630 / p 3e-139	20.2 EB05 15.2 · IC025 +3.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 21.5 · 71% consumer	no trial data cached
Irritable bowel syndrome	20	23.6 15.3–36.4ROR 24.2 · χ² 411 / p 1e-91	23.1 EB05 15.7 · IC025 +3.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 25.8	no trial data cached
Haemorrhoids	12	15.5 8.8–27.2ROR 15.7 · χ² 148 / p 2e-34	14.3 EB05 7.8 · IC025 +2.3 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 23.3	no trial data cached
Pharmaceutical product complaint	10	9.6 5.2–17.7ROR 9.7 · χ² 68 / p 6e-17	7.5 EB05 4.1 · IC025 +1.7 3/3 methods agree	Not in label — unassessed	–	no trial data cached
Diarrhoea haemorrhagic	10	26.9 14.5–49.9ROR 27.3 · χ² 224 / p 5e-51	25.6 EB05 14.6 · IC025 +2.5 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 38.2	no trial data cached
Hernia	8	10.5 5.3–20.9ROR 10.6 · χ² 59 / p 6e-15	7.9 EB05 3.9 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 9.7	no trial data cached
Small intestinal obstruction	8	16.4 8.2–32.8ROR 16.6 · χ² 101 / p 4e-24	14.2 EB05 6.3 · IC025 +1.9 3/3 methods agree	Labeled (related wording) related wording	serious PRR 21.9	no trial data cached
Gastrointestinal pain	7	16.1 7.7–33.7ROR 16.2 · χ² 85 / p 2e-20	13.3 EB05 5.4 · IC025 +1.7 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 4.6	no trial data cached
Intestinal perforation	6	13.5 6.1–29.9ROR 13.6 · χ² 57 / p 2e-14	9.8 EB05 3.9 · IC025 +1.4 3/3 methods agree	Labeled — boxed warning synonym match	serious PRR 17.9	no trial data cached
Anorexia	5	9.6 4.0–23.1ROR 9.7 · χ² 31 / p 2e-8	6.1 EB05 2.6 · IC025 +0.9 3/3 methods agree	Not in label — unassessed	serious PRR 10.1	no trial data cached
Coeliac disease	3	7.7 2.5–23.8ROR 7.7 · χ² 11 / p 4e-4	4.2 EB05 1.6 · IC025 -0.1 PRR-only: not supported by EBGM or IC	Not in label — unassessed	serious PRR 8.5	no trial data cached

Unlabeled candidate signals

Every screened signal with n ≥ 20 was either labeled, an indication term, or an artifact pattern — no unlabeled candidate stood out in the top signals.

Want to assess one of these properly? The runbook describes the Bradford Hill / trial-evidence workflow used on the assessment page, and handoff_top1000_signals.csv lists the strongest unassessed pairs across all drugs.

Common questions

What are the most reported side effects of Alosetron?

In FDA FAERS, the most frequently co-reported reaction terms for Alosetron are constipation, rectal haemorrhage, irritable bowel syndrome, haemorrhoids, pharmaceutical product complaint, diarrhoea haemorrhagic. These are report counts, not rates: FAERS has no denominator, reporting is voluntary and uneven, and a term can be reported because of the illness being treated rather than the drug.

Does Alosetron have an FDA boxed warning?

Yes. The current FDA label carries a boxed warning: SERIOUS GASTROINTESTINAL ADVERSE REACTIONS Infrequent but serious gastrointestinal adverse reactions have been reported with the use of alosetron tablets. These events, including ischemic colitis and serious complications of constipation, have resulted in hospitalization, and rarely, blood transfusion, surgery, and death.

Do FAERS signals prove that Alosetron causes these side effects?

No. A disproportionality signal (PRR, ROR) means a reaction is reported more often with this drug than with others in the database. That can reflect a real effect, but also the disease being treated, stimulated reporting after news or litigation, co-medications, or how reports are coded. Causality needs temporality, dose-response, biological plausibility, consistency across data sources and, ideally, trial or cohort evidence. This page screens each term against the FDA label and ClinicalTrials.gov results; it does not establish causation.

Sources & methods

FDA label via openFDA (set ID 2846a244-7540-442b-81bc-638e641497ce, effective 20251001; matched on openfda.generic_name.exact:"ALOSETRON")
Bayesian shrinkage measures computed offline over all 1,317,300 cached pairs: BCPNN information component (IC, with Norén closed-form IC025) and MGPS empirical-Bayes geometric mean (EBGM, EB05) with a two-component gamma prior fitted by maximum marginal likelihood (α₁=0.57, β₁=0.02, α₂=1.42, β₂=0.70, w=0.17); unstratified
FAERS pair statistics from the OpenPV build of 2026-09-14 (openFDA count= aggregation, field patient.drug.openfda.generic_name.exact, 13 reaction terms, min 3 co-reports); PRR/ROR with 95% CI, chi-square with Yates correction
Serious-only and stratified counts (serious:1, patient.patientsex, primarysource.qualification) from openFDA count queries; serious-only PRR uses the drug serious report total and the term global serious total (N_serious=11,882,979); strata shown only when n ≥ 20
Seriousness and sex counts from openFDA count=serious, patient.patientsex, seriousnessdeath

Page generated 2026-10-08. Label and PubChem text are retrieved automatically and may lag the current label; always check the current prescribing information. OpenPV is a beta research tool of the Open Source Medicine Foundation.