Clemastine side effects: what 1,356 FDA adverse event reports show
Drug class
Not stated in label
Label matched
Clemastine Fumarate (Clemastine Fumarate)
Who reports
1,356 reports · 92% serious · 174 with death outcome · 61% female
Used for
Clemastine Fumarate Tablets USP, 2.68 mg are indicated for the relief of symptoms associated with allergic rhinitis such as sneezing, rhinorrhea, pruritus, and lacrimation. Clemastine Fumarate Tablets USP, 2.68 mg are also indicated for the relief of mild, uncomplicated allergic skin manifestations of urticaria and angioedema.
What it is
DESCRIPTION Clemastine belongs to the benzhydryl ether group of antihistaminic compounds.
Boxed warning
None in the current label
Causality screen of the 25 strongest signals
What the badges mean
- 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.
- Lab value / disease marker A laboratory result, investigation or disease-activity marker (antibody positive, CRP abnormal, swollen joint count) not described in the label. These usually mirror the monitored disease or testing protocol rather than a drug effect; not screened further.
- 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. 27 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Toxic epidermal necrolysis (severe skin peeling reaction) | 61 | 62.8 49.2–80.4ROR 65.8 · χ² 3,639 / p <1e-300 | 61.4 EB05 49.6 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious PRR 39.3 | no trial data cached |
| Cytokine release syndrome | 46 | 37.4 28.2–49.8ROR 38.7 · χ² 1,593 / p <1e-300 | 36.8 EB05 28.7 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious PRR 23.7 · 98% clinician | no trial data cached |
| Conjunctivitis | 35 | 29.5 21.3–41.0ROR 30.3 · χ² 935 / p 1e-205 | 29.1 EB05 21.8 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious PRR 34.3 · ♀ 85% (drug 61%) | no trial data cached |
| Cytomegalovirus infection | 25 | 23.3 15.8–34.4ROR 23.7 · χ² 511 / p 2e-113 | 22.9 EB05 16.3 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious PRR 14.8 · ♀ 100% (drug 61%) · 100% clinician | no trial data cached |
| Stevens-johnson syndrome (severe blistering skin reaction) | 28 | 19.5 13.5–28.1ROR 19.9 · χ² 472 / p 5e-105 | 19.2 EB05 13.9 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 12.3 · 100% clinician | no trial data cached |
| Mouth ulceration | 23 | 16.9 11.3–25.4ROR 17.2 · χ² 329 / p 7e-74 | 16.6 EB05 11.4 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 14.1 · ♀ 100% (drug 61%) | no trial data cached |
| Blood lactate dehydrogenase increased | 17 | 16.5 10.3–26.5ROR 16.7 · χ² 232 / p 9e-53 | 15.9 EB05 10.0 · IC025 +2.7 3/3 methods agree | Lab value / disease marker | serious PRR 11.0 | no trial data cached |
| Circulatory collapse | 15 | 13.6 8.2–22.5ROR 13.7 · χ² 162 / p 2e-37 | 12.5 EB05 7.4 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 8.5 | no trial data cached |
| Gamma-glutamyltransferase increased | 19 | 13.3 8.5–20.7ROR 13.4 · χ² 203 / p 2e-46 | 12.5 EB05 7.9 · IC025 +2.6 3/3 methods agree | Lab value / disease marker | serious PRR 8.7 | no trial data cached |
| Leukopenia (low white blood cells) | 41 | 12.7 9.4–17.2ROR 13.1 · χ² 432 / p 3e-96 | 12.4 EB05 9.4 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 8.3 · 98% clinician | no trial data cached |
| Rash maculo-papular | 18 | 12.6 7.9–19.9ROR 12.7 · χ² 181 / p 2e-41 | 11.6 EB05 7.3 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 8.8 | no trial data cached |
| Cardiovascular disorder | 20 | 12.1 7.8–18.7ROR 12.3 · χ² 193 / p 4e-44 | 11.2 EB05 7.2 · IC025 +2.5 3/3 methods agree | Labeled (related wording) related wording | serious PRR 8.2 · ♀ 90% (drug 61%) | no trial data cached |
| Leukocytosis | 13 | 11.1 6.5–19.1ROR 11.2 · χ² 110 / p 5e-26 | 9.6 EB05 5.4 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 7.2 | no trial data cached |
| Blood creatinine increased | 47 | 11.1 8.4–14.7ROR 11.5 · χ² 424 / p 2e-94 | 10.8 EB05 8.3 · IC025 +2.8 3/3 methods agree | Lab value / disease marker | serious PRR 8.0 · ♀ 92% (drug 61%) · 98% clinician | no trial data cached |
| Blister | 40 | 11.1 8.1–15.0ROR 11.4 · χ² 357 / p 8e-80 | 10.6 EB05 8.0 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 11.5 | no trial data cached |
| Drug reaction with eosinophilia and systemic symptoms | 18 | 10.9 6.9–17.3ROR 11.0 · χ² 152 / p 3e-35 | 9.8 EB05 6.2 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 6.8 | no trial data cached |
| Infusion related reaction (reaction during infusion) | 45 | 10.5 7.9–14.1ROR 10.9 · χ² 380 / p 5e-85 | 10.1 EB05 7.7 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 8.0 · 93% clinician | no trial data cached |
| Coronary artery disease | 16 | 8.1 5.0–13.2ROR 8.2 · χ² 93 / p 3e-22 | 6.9 EB05 4.4 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 5.2 | no trial data cached |
| Angioedema (deep swelling of face/throat) | 22 | 7.7 5.1–11.7ROR 7.8 · χ² 122 / p 1e-28 | 6.8 EB05 4.7 · IC025 +2.0 3/3 methods agree | Likely indication confounding term in indications | serious PRR 5.1 · 95% clinician | no trial data cached |
| Cardiac failure (heart failure) | 40 | 7.7 5.7–10.5ROR 7.9 · χ² 228 / p 1e-51 | 7.2 EB05 5.5 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 4.9 · ♀ 36% (drug 61%) | no trial data cached |
| Anaphylactic reaction (severe allergic reaction) | 26 | 7.3 5.0–10.7ROR 7.5 · χ² 136 / p 9e-32 | 6.6 EB05 4.7 · IC025 +2.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 4.7 | no trial data cached |
| Anaphylactic shock | 12 | 7.2 4.1–12.7ROR 7.3 · χ² 59 / p 1e-14 | 5.9 EB05 3.5 · IC025 +1.6 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 4.6 | no trial data cached |
| Haematoma | 11 | 6.5 3.6–11.8ROR 6.6 · χ² 46 / p 5e-12 | 5.3 EB05 3.1 · IC025 +1.4 3/3 methods agree | Not in label — unassessed | serious PRR 4.5 | no trial data cached |
| Erythema (skin redness) | 80 | 6.0 4.9–7.5ROR 6.3 · χ² 334 / p 6e-75 | 5.8 EB05 4.8 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 8.1 · ♀ 89% (drug 61%) | no trial data cached |
| Neutropenia (low neutrophils (infection-fighting cells)) | 49 | 5.6 4.3–7.4ROR 5.8 · χ² 182 / p 1e-41 | 5.3 EB05 4.2 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 3.7 | no trial data cached |
Trial evidence (ClinicalTrials.gov)
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 |
|---|---|---|---|---|---|---|
| Erythema (skin redness) | 80 | 6.0 4.9–7.5ROR 6.3 · χ² 334 / p 6e-75 | 5.8 EB05 4.8 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 8.1 · ♀ 89% (drug 61%) | no trial data cached |
| Toxic epidermal necrolysis (severe skin peeling reaction) | 61 | 62.8 49.2–80.4ROR 65.8 · χ² 3,639 / p <1e-300 | 61.4 EB05 49.6 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious PRR 39.3 | no trial data cached |
| Neutropenia (low neutrophils (infection-fighting cells)) | 49 | 5.6 4.3–7.4ROR 5.8 · χ² 182 / p 1e-41 | 5.3 EB05 4.2 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 3.7 | no trial data cached |
| Blood creatinine increased | 47 | 11.1 8.4–14.7ROR 11.5 · χ² 424 / p 2e-94 | 10.8 EB05 8.3 · IC025 +2.8 3/3 methods agree | Lab value / disease marker | serious PRR 8.0 · ♀ 92% (drug 61%) · 98% clinician | no trial data cached |
| Cytokine release syndrome | 46 | 37.4 28.2–49.8ROR 38.7 · χ² 1,593 / p <1e-300 | 36.8 EB05 28.7 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious PRR 23.7 · 98% clinician | no trial data cached |
| Infusion related reaction (reaction during infusion) | 45 | 10.5 7.9–14.1ROR 10.9 · χ² 380 / p 5e-85 | 10.1 EB05 7.7 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 8.0 · 93% clinician | no trial data cached |
| Leukopenia (low white blood cells) | 41 | 12.7 9.4–17.2ROR 13.1 · χ² 432 / p 3e-96 | 12.4 EB05 9.4 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 8.3 · 98% clinician | no trial data cached |
| Cardiac failure (heart failure) | 40 | 7.7 5.7–10.5ROR 7.9 · χ² 228 / p 1e-51 | 7.2 EB05 5.5 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 4.9 · ♀ 36% (drug 61%) | no trial data cached |
| Blister | 40 | 11.1 8.1–15.0ROR 11.4 · χ² 357 / p 8e-80 | 10.6 EB05 8.0 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 11.5 | no trial data cached |
| Conjunctivitis | 35 | 29.5 21.3–41.0ROR 30.3 · χ² 935 / p 1e-205 | 29.1 EB05 21.8 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious PRR 34.3 · ♀ 85% (drug 61%) | no trial data cached |
| Stevens-johnson syndrome (severe blistering skin reaction) | 28 | 19.5 13.5–28.1ROR 19.9 · χ² 472 / p 5e-105 | 19.2 EB05 13.9 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 12.3 · 100% clinician | no trial data cached |
| Anaphylactic reaction (severe allergic reaction) | 26 | 7.3 5.0–10.7ROR 7.5 · χ² 136 / p 9e-32 | 6.6 EB05 4.7 · IC025 +2.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 4.7 | no trial data cached |
| Cytomegalovirus infection | 25 | 23.3 15.8–34.4ROR 23.7 · χ² 511 / p 2e-113 | 22.9 EB05 16.3 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious PRR 14.8 · ♀ 100% (drug 61%) · 100% clinician | no trial data cached |
| Mouth ulceration | 23 | 16.9 11.3–25.4ROR 17.2 · χ² 329 / p 7e-74 | 16.6 EB05 11.4 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 14.1 · ♀ 100% (drug 61%) | no trial data cached |
| Angioedema (deep swelling of face/throat) | 22 | 7.7 5.1–11.7ROR 7.8 · χ² 122 / p 1e-28 | 6.8 EB05 4.7 · IC025 +2.0 3/3 methods agree | Likely indication confounding term in indications | serious PRR 5.1 · 95% clinician | no trial data cached |
Unlabeled candidate signals
These flagged terms were not found in the FDA label text and do not match an artifact pattern. They are the pairs that would merit a structured assessment (temporality, dose-response, biological plausibility, consistency across databases, trial or cohort evidence). The screen has not done that; string-matching misses label wording, and a strong PRR can still be stimulated reporting, co-medication, or the disease itself.
- Toxic epidermal necrolysis — n=61, PRR 62.8
- Cytokine release syndrome — n=46, PRR 37.4
- Conjunctivitis — n=35, PRR 29.5
- Cytomegalovirus infection — n=25, PRR 23.3
- Stevens-johnson syndrome — n=28, PRR 19.5
- Mouth ulceration — n=23, PRR 16.9
- Leukopenia — n=41, PRR 12.7
- Blister — n=40, PRR 11.1
- Infusion related reaction — n=45, PRR 10.5
- Cardiac failure — n=40, PRR 7.7
✓ A hand-written Bradford Hill causality assessment exists for this drug: Tenofovir disoproxil fumarate ↔ Bone loss.
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 Clemastine?
In FDA FAERS, the most frequently co-reported reaction terms for Clemastine are erythema, toxic epidermal necrolysis, neutropenia, blood creatinine increased, cytokine release syndrome, infusion related reaction. 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 Clemastine have an FDA boxed warning?
No. The FDA label retrieved for Clemastine has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Clemastine 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 cf8a3449-8bb3-4d5c-8d0d-557590e49ee5, effective 20250203; matched on
openfda.generic_name.exact:"CLEMASTINE FUMARATE") - 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, fieldpatient.drug.openfda.generic_name.exact, 52 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.