Felbamate side effects: what 1,751 FDA adverse event reports show
Who reports
1,751 reports · 71% serious · 89 with death outcome · 52% female
Used for
Felbamate oral suspension, USP is not indicated as a first line antiepileptic treatment (see Warnings ). Felbamate oral suspension is recommended for use only in those patients who respond inadequately to alternative treatments and whose epilepsy is so severe that a substantial risk of aplastic anemia and/or liver failure is deemed acceptable in light of the benefits conferred by its use.
What it is
DESCRIPTION Felbamate oral suspension, USP is an antiepileptic available as 600 mg/5 mL suspension for oral administration.
Boxed warning
1. APLASTIC ANEMIA THE USE OF FELBAMATE ORAL SUSPENSION, USP IS ASSOCIATED WITH A MARKED INCREASE IN THE INCIDENCE OF APLASTIC ANEMIA. ACCORDINGLY, FELBAMATE ORAL SUSPENSION SHOULD ONLY BE USED IN PATIENTS WHOSE EPILEPSY IS SO SEVERE THAT THE RISK OF APLASTIC ANEMIA IS DEEMED ACCEPTABLE IN LIGHT OF THE BENEFITS CONFERRED BY ITS USE (SEE INDICATIONS ).
Causality screen of the 34 strongest signals
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. 21 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 |
|---|---|---|---|---|---|---|
| Generalised tonic-clonic seizure | 66 | 48.5 38.3–61.5ROR 50.4 · χ² 3,013 / p <1e-300 | 47.7 EB05 38.8 · IC025 +4.7 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 36.6 | no trial data cached |
| Seizure | 352 | 36.8 33.6–40.5ROR 45.9 · χ² 12,267 / p <1e-300 | 36.7 EB05 33.6 · IC025 +5.0 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 27.1 | no trial data cached |
| Status epilepticus | 31 | 32.9 23.2–46.6ROR 33.5 · χ² 925 / p 2e-203 | 32.2 EB05 23.8 · IC025 +3.8 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 26.6 · 90% clinician | no trial data cached |
| Convulsion (seizure) | 124 | 25.7 21.6–30.4ROR 27.5 · χ² 2,915 / p <1e-300 | 25.5 EB05 22.0 · IC025 +4.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 20.5 | no trial data cached |
| Epilepsy | 49 | 19.3 14.6–25.4ROR 19.8 · χ² 830 / p 9e-183 | 19.1 EB05 15.0 · IC025 +3.5 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 15.7 | no trial data cached |
| Grand mal convulsion | 15 | 19.2 11.6–31.8ROR 19.4 · χ² 241 / p 1e-54 | 18.5 EB05 11.6 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 15.8 | no trial data cached |
| Ventricular extrasystoles | 14 | 16.1 9.6–27.2ROR 16.3 · χ² 184 / p 4e-42 | 15.2 EB05 8.9 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 14.5 | no trial data cached |
| Sinus bradycardia | 13 | 16.1 9.4–27.7ROR 16.2 · χ² 169 / p 6e-39 | 15.1 EB05 8.6 · IC025 +2.4 3/3 methods agree | Labeled (related wording) related wording | serious PRR 13.4 | no trial data cached |
| Mitral valve incompetence | 15 | 15.9 9.6–26.3ROR 16.0 · χ² 195 / p 2e-44 | 15.1 EB05 9.0 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 12.9 | no trial data cached |
| Drug level decreased | 13 | 15.2 8.9–26.2ROR 15.3 · χ² 159 / p 1e-36 | 14.1 EB05 8.0 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious PRR 10.5 | no trial data cached |
| Hypotonia | 10 | 12.0 6.4–22.2ROR 12.0 · χ² 90 / p 1e-21 | 9.9 EB05 5.0 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 11.1 | no trial data cached |
| Drug reaction with eosinophilia and systemic symptoms | 24 | 11.3 7.6–16.8ROR 11.4 · χ² 214 / p 8e-49 | 10.5 EB05 7.1 · IC025 +2.5 3/3 methods agree | Labeled (related wording) related wording | serious PRR 9.1 · ♀ 100% (drug 52%) · 96% clinician | no trial data cached |
| Circulatory collapse | 16 | 11.2 6.9–18.3ROR 11.3 · χ² 139 / p 2e-32 | 10.0 EB05 6.0 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 9.1 | no trial data cached |
| Myoclonus | 11 | 11.1 6.1–19.9ROR 11.1 · χ² 91 / p 8e-22 | 9.2 EB05 4.9 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 7.7 | no trial data cached |
| Sedation | 24 | 11.0 7.4–16.4ROR 11.2 · χ² 209 / p 1e-47 | 10.2 EB05 6.9 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 8.7 | no trial data cached |
| Pneumonia aspiration | 19 | 9.1 5.8–14.3ROR 9.2 · χ² 130 / p 2e-30 | 8.0 EB05 5.2 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 7.4 | no trial data cached |
| Lethargy | 41 | 8.5 6.3–11.6ROR 8.7 · χ² 266 / p 4e-60 | 8.0 EB05 6.1 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 8.2 | no trial data cached |
| Hypersomnia | 20 | 8.4 5.4–12.9ROR 8.5 · χ² 123 / p 8e-29 | 7.4 EB05 4.9 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious PRR 6.2 | no trial data cached |
| Drug level increased | 11 | 8.0 4.4–14.3ROR 8.0 · χ² 60 / p 4e-15 | 6.3 EB05 3.7 · IC025 +1.6 3/3 methods agree | Reporting / coding artifact | serious PRR 5.2 | no trial data cached |
| Nephrolithiasis (kidney stones) | 30 | 7.9 5.5–11.2ROR 8.0 · χ² 173 / p 8e-40 | 7.2 EB05 5.2 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 6.5 · ♀ 21% (drug 52%) | no trial data cached |
| Aggression | 32 | 7.6 5.4–10.8ROR 7.8 · χ² 179 / p 5e-41 | 7.0 EB05 5.2 · IC025 +2.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 4.3 · ♀ 30% (drug 52%) | no trial data cached |
| Diplopia (double vision) | 16 | 7.4 4.5–12.0ROR 7.4 · χ² 82 / p 7e-20 | 6.3 EB05 4.0 · IC025 +1.8 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 6.1 | no trial data cached |
| Abnormal behaviour | 24 | 7.2 4.8–10.7ROR 7.3 · χ² 122 / p 9e-29 | 6.5 EB05 4.5 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 6.0 | no trial data cached |
| Aphasia (loss of speech) | 18 | 7.1 4.5–11.3ROR 7.2 · χ² 89 / p 2e-21 | 6.2 EB05 4.1 · IC025 +1.8 3/3 methods agree | Not in label — unassessed | serious PRR 5.0 | no trial data cached |
| Joint injury | 12 | 6.7 3.8–11.8ROR 6.8 · χ² 53 / p 2e-13 | 5.5 EB05 3.3 · IC025 +1.5 3/3 methods agree | Not in label — unassessed | serious PRR 7.1 | no trial data cached |
| Somnolence (drowsiness) | 110 | 6.6 5.5–7.9ROR 6.9 · χ² 517 / p 9e-115 | 6.4 EB05 5.4 · IC025 +2.4 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 6.4 | no trial data cached |
| Prescribed overdose | 10 | 6.2 3.3–11.5ROR 6.2 · χ² 38 / p 3e-10 | 5.0 EB05 2.9 · IC025 +1.2 3/3 methods agree | Not in label — unassessed | serious PRR 2.6 | no trial data cached |
| Product substitution issue | 29 | 6.0 4.2–8.7ROR 6.1 · χ² 117 / p 1e-27 | 5.5 EB05 4.0 · IC025 +1.9 3/3 methods agree | Reporting / coding artifact | serious PRR 9.3 · ♀ 29% (drug 52%) | no trial data cached |
| Treatment failure | 41 | 6.0 4.4–8.1ROR 6.1 · χ² 166 / p 3e-38 | 5.6 EB05 4.3 · IC025 +2.0 3/3 methods agree | Reporting / coding artifact | serious PRR 7.9 · 90% clinician | no trial data cached |
| Drug ineffective for unapproved indication | 27 | 5.8 4.0–8.4ROR 5.9 · χ² 103 / p 2e-24 | 5.3 EB05 3.8 · IC025 +1.8 3/3 methods agree | Reporting / coding artifact | serious PRR 7.0 · ♀ 73% (drug 52%) | no trial data cached |
| Depressed level of consciousness | 19 | 5.8 3.7–9.0ROR 5.8 · χ² 70 / p 3e-17 | 5.1 EB05 3.5 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 4.8 | no trial data cached |
| Irritability | 27 | 5.4 3.7–7.8ROR 5.4 · χ² 92 / p 4e-22 | 4.9 EB05 3.6 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 4.0 | no trial data cached |
| Toxicity to various agents | 71 | 5.1 4.0–6.4ROR 5.2 · χ² 230 / p 4e-52 | 4.9 EB05 4.0 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 4.2 · 94% clinician | no trial data cached |
| Psychotic disorder | 11 | 4.5 2.5–8.0ROR 4.5 · χ² 26 / p 2e-7 | 3.8 EB05 2.3 · IC025 +0.9 3/3 methods agree | Not in label — unassessed | serious PRR 3.6 | 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 |
|---|---|---|---|---|---|---|
| Seizure | 352 | 36.8 33.6–40.5ROR 45.9 · χ² 12,267 / p <1e-300 | 36.7 EB05 33.6 · IC025 +5.0 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 27.1 | no trial data cached |
| Convulsion (seizure) | 124 | 25.7 21.6–30.4ROR 27.5 · χ² 2,915 / p <1e-300 | 25.5 EB05 22.0 · IC025 +4.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 20.5 | no trial data cached |
| Somnolence (drowsiness) | 110 | 6.6 5.5–7.9ROR 6.9 · χ² 517 / p 9e-115 | 6.4 EB05 5.4 · IC025 +2.4 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 6.4 | no trial data cached |
| Toxicity to various agents | 71 | 5.1 4.0–6.4ROR 5.2 · χ² 230 / p 4e-52 | 4.9 EB05 4.0 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 4.2 · 94% clinician | no trial data cached |
| Generalised tonic-clonic seizure | 66 | 48.5 38.3–61.5ROR 50.4 · χ² 3,013 / p <1e-300 | 47.7 EB05 38.8 · IC025 +4.7 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 36.6 | no trial data cached |
| Epilepsy | 49 | 19.3 14.6–25.4ROR 19.8 · χ² 830 / p 9e-183 | 19.1 EB05 15.0 · IC025 +3.5 3/3 methods agree | Labeled — boxed warning exact term | serious PRR 15.7 | no trial data cached |
| Treatment failure | 41 | 6.0 4.4–8.1ROR 6.1 · χ² 166 / p 3e-38 | 5.6 EB05 4.3 · IC025 +2.0 3/3 methods agree | Reporting / coding artifact | serious PRR 7.9 · 90% clinician | no trial data cached |
| Lethargy | 41 | 8.5 6.3–11.6ROR 8.7 · χ² 266 / p 4e-60 | 8.0 EB05 6.1 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 8.2 | no trial data cached |
| Aggression | 32 | 7.6 5.4–10.8ROR 7.8 · χ² 179 / p 5e-41 | 7.0 EB05 5.2 · IC025 +2.2 3/3 methods agree | Labeled (related wording) related wording | serious PRR 4.3 · ♀ 30% (drug 52%) | no trial data cached |
| Status epilepticus | 31 | 32.9 23.2–46.6ROR 33.5 · χ² 925 / p 2e-203 | 32.2 EB05 23.8 · IC025 +3.8 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 26.6 · 90% clinician | no trial data cached |
| Nephrolithiasis (kidney stones) | 30 | 7.9 5.5–11.2ROR 8.0 · χ² 173 / p 8e-40 | 7.2 EB05 5.2 · IC025 +2.2 3/3 methods agree | Not in label — unassessed | serious PRR 6.5 · ♀ 21% (drug 52%) | no trial data cached |
| Product substitution issue | 29 | 6.0 4.2–8.7ROR 6.1 · χ² 117 / p 1e-27 | 5.5 EB05 4.0 · IC025 +1.9 3/3 methods agree | Reporting / coding artifact | serious PRR 9.3 · ♀ 29% (drug 52%) | no trial data cached |
| Irritability | 27 | 5.4 3.7–7.8ROR 5.4 · χ² 92 / p 4e-22 | 4.9 EB05 3.6 · IC025 +1.7 3/3 methods agree | Not in label — unassessed | serious PRR 4.0 | no trial data cached |
| Drug ineffective for unapproved indication | 27 | 5.8 4.0–8.4ROR 5.9 · χ² 103 / p 2e-24 | 5.3 EB05 3.8 · IC025 +1.8 3/3 methods agree | Reporting / coding artifact | serious PRR 7.0 · ♀ 73% (drug 52%) | no trial data cached |
| Drug dose omission | 26 | 1.9 1.3–2.7ROR 1.9 · χ² 10 / p 0.001 | 1.8 EB05 1.3 · IC025 +0.2 | Reporting / coding artifact | serious PRR 3.5 | 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.
- Sedation — n=24, PRR 11.0
- Lethargy — n=41, PRR 8.5
- Hypersomnia — n=20, PRR 8.4
- Nephrolithiasis — n=30, PRR 7.9
- Abnormal behaviour — n=24, PRR 7.2
- Irritability — n=27, PRR 5.4
- Toxicity to various agents — n=71, PRR 5.1
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 Felbamate?
In FDA FAERS, the most frequently co-reported reaction terms for Felbamate are seizure, convulsion, somnolence, toxicity to various agents, generalised tonic-clonic seizure, epilepsy. 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 Felbamate have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: 1. APLASTIC ANEMIA THE USE OF FELBAMATE ORAL SUSPENSION, USP IS ASSOCIATED WITH A MARKED INCREASE IN THE INCIDENCE OF APLASTIC ANEMIA. ACCORDINGLY, FELBAMATE ORAL SUSPENSION SHOULD ONLY BE USED IN PATIENTS WHOSE EPILEPSY IS SO SEVERE THAT THE RISK OF APLASTIC ANEMIA IS DEEMED ACCEPTABLE IN LIGHT OF THE BENEFITS CONFERRED BY ITS USE (SEE INDICATIONS ).
Do FAERS signals prove that Felbamate 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 0afffb17-e6ac-4bea-a90e-7ef3c8150290, effective 20260714; matched on
openfda.generic_name.exact:"FELBAMATE") - 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, 55 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.