Drug · FAERS side-effect profile with label screen
Zonisamide side effects: what 10,552 FDA adverse event reports show
Who reports
10,552 reports · 77% serious · 677 with death outcome · 60% female
openFDA FAERS counts, all years, deduplication not applied
Used for
Zonisamide Capsules are indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.
FDA label, Indications and Usage
What it is
DESCRIPTION Zonisamide Capsules USP, are an antiseizure drug chemically classified as a sulfonamide and unrelated to other antiseizure agents. The active ingredient is zonisamide, 1,2 -benzisoxazole-3-methanesulfonamide.
FDA label, Description section
Boxed warning
None in the current 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 40 strongest signals
Labeled adverse reaction 2Labeled (related wording) 4Likely indication confounding 8Reporting / coding artifact 1Lab value / disease marker 2Not in label — unassessed 23
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.
- 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.
- 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. 1,070 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
Show:
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Epilepsy with myoclonic-atonic seizures | 11 | 909.8 426.2–1,941.9ROR 910.4 · χ² 5,523 / p <1e-300 | 282.0 EB05 168.0 · IC025 +3.4 3/3 methods agree | Labeled (related wording) related wording | serious n=11 | not reported in cached trials |
| Tuberous sclerosis complex | 27 | 499.5 322.1–774.7ROR 500.4 · χ² 9,547 / p <1e-300 | 292.4 EB05 211.1 · IC025 +4.9 3/3 methods agree | Not in label — unassessed | serious n=26 | not reported in cached trials |
| Tonsillar exudate | 10 | 426.1 210.0–864.3ROR 426.3 · χ² 2,936 / p <1e-300 | 201.8 EB05 117.1 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Brain lobectomy | 13 | 415.4 223.8–771.1ROR 415.8 · χ² 3,835 / p <1e-300 | 218.3 EB05 135.8 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Hereditary optic atrophy | 10 | 238.3 121.9–465.7ROR 238.5 · χ² 1,823 / p <1e-300 | 147.3 EB05 85.5 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=9 | not reported in cached trials |
| Postictal psychosis | 20 | 211.4 132.2–338.2ROR 211.7 · χ² 3,460 / p <1e-300 | 156.7 EB05 107.1 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=19 | not reported in cached trials |
| Congenital intestinal malformation | 13 | 177.5 99.7–315.9ROR 177.6 · χ² 1,872 / p <1e-300 | 128.4 EB05 79.9 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Atonic seizures | 84 | 168.0 134.1–210.5ROR 169.0 · χ² 12,308 / p <1e-300 | 145.3 EB05 121.0 · IC025 +6.0 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=65 | not reported in cached trials |
| Multiple-drug resistance | 288 | 146.4 129.8–165.1ROR 149.3 · χ² 37,540 / p <1e-300 | 131.5 EB05 119.3 · IC025 +6.6 3/3 methods agree | Reporting / coding artifact | serious n=222 · 96% clinician | not reported in cached trials |
| Vagal nerve stimulator implantation | 27 | 142.7 96.1–212.0ROR 143.0 · χ² 3,322 / p <1e-300 | 118.9 EB05 85.8 · IC025 +4.6 3/3 methods agree | Not in label — unassessed | serious n=14 | not reported in cached trials |
| Postictal paralysis | 21 | 135.4 86.6–211.9ROR 135.6 · χ² 2,435 / p <1e-300 | 111.4 EB05 76.8 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=21 | not reported in cached trials |
| Congenital aplasia | 22 | 117.2 75.9–181.0ROR 117.3 · χ² 2,233 / p <1e-300 | 99.1 EB05 69.0 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious n=22 | not reported in cached trials |
| Sudden unexplained death in epilepsy | 38 | 107.7 77.5–149.8ROR 108.0 · χ² 3,633 / p <1e-300 | 95.4 EB05 72.6 · IC025 +4.9 3/3 methods agree | Labeled (related wording) related wording | serious n=32 | not reported in cached trials |
| Seizure cluster | 53 | 100.6 76.1–132.8ROR 100.9 · χ² 4,783 / p <1e-300 | 90.9 EB05 72.2 · IC025 +5.2 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=32 · ♀ 33% (drug 60%) | not reported in cached trials |
| Neonatal pneumonia | 15 | 97.6 57.9–164.7ROR 97.7 · χ² 1,253 / p 1e-274 | 82.1 EB05 52.8 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| Change in seizure presentation | 40 | 92.5 67.2–127.3ROR 92.7 · χ² 3,312 / p <1e-300 | 83.5 EB05 64.0 · IC025 +4.9 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=32 · ♀ 83% (drug 60%) | not reported in cached trials |
| Vestibular migraine | 13 | 83.8 47.9–146.7ROR 83.9 · χ² 928 / p 5e-204 | 71.2 EB05 44.3 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| Retinogram abnormal | 14 | 78.1 45.6–133.8ROR 78.2 · χ² 938 / p 3e-206 | 67.5 EB05 42.8 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=13 | not reported in cached trials |
| Epileptic encephalopathy | 11 | 74.7 40.7–137.0ROR 74.8 · χ² 691 / p 1e-152 | 63.5 EB05 37.9 · IC025 +3.1 3/3 methods agree | Labeled (related wording) related wording | serious n=11 | not reported in cached trials |
| Human herpes virus 6 serology positive | 11 | 74.4 40.6–136.3ROR 74.4 · χ² 688 / p 6e-152 | 63.3 EB05 37.7 · IC025 +3.1 3/3 methods agree | Lab value / disease marker | serious n=10 | not reported in cached trials |
| Herpes oesophagitis | 10 | 69.6 36.9–131.3ROR 69.7 · χ² 581 / p 1e-128 | 59.3 EB05 34.4 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Infantile spasms | 32 | 66.8 46.8–95.1ROR 66.9 · χ² 1,916 / p <1e-300 | 61.5 EB05 45.6 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=24 | not reported in cached trials |
| Focal dyscognitive seizures | 50 | 65.2 49.1–86.6ROR 65.4 · χ² 2,960 / p <1e-300 | 61.0 EB05 48.1 · IC025 +4.8 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=34 | not reported in cached trials |
| Myoclonic epilepsy | 62 | 62.6 48.6–80.7ROR 62.9 · χ² 3,541 / p <1e-300 | 59.0 EB05 47.6 · IC025 +4.9 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=46 | not reported in cached trials |
| Neonatal hypotension | 15 | 60.8 36.3–101.9ROR 60.8 · χ² 789 / p 7e-174 | 54.5 EB05 35.1 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | – | not reported in cached trials |
| Deja vu | 11 | 59.9 32.8–109.6ROR 60.0 · χ² 556 / p 3e-123 | 52.6 EB05 31.3 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Human herpesvirus 6 infection reactivation | 14 | 59.8 35.1–102.1ROR 59.9 · χ² 721 / p 3e-159 | 53.5 EB05 33.9 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=14 | not reported in cached trials |
| Complex partial seizures | 43 | 56.5 41.7–76.6ROR 56.7 · χ² 2,201 / p <1e-300 | 53.1 EB05 41.1 · IC025 +4.6 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=23 | NCT00477295: 1/281 (0.4%) on Zonisamide (serious AE) |
| Tonic convulsion | 50 | 52.7 39.8–69.9ROR 52.9 · χ² 2,395 / p <1e-300 | 49.9 EB05 39.4 · IC025 +4.6 3/3 methods agree | Not in label — unassessed | serious n=44 | not reported in cached trials |
| Foetal malformation | 39 | 52.6 38.2–72.4ROR 52.8 · χ² 1,854 / p <1e-300 | 49.6 EB05 37.9 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=38 | not reported in cached trials |
| Partial seizures with secondary generalisation | 15 | 47.1 28.1–78.7ROR 47.1 · χ² 611 / p 4e-135 | 43.3 EB05 27.8 · IC025 +3.4 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=14 | not reported in cached trials |
| Tonsillar inflammation | 10 | 45.4 24.2–85.1ROR 45.4 · χ² 378 / p 1e-84 | 40.8 EB05 23.7 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious n=10 | not reported in cached trials |
| Choroidal effusion | 24 | 44.1 29.4–66.2ROR 44.2 · χ² 939 / p 2e-206 | 41.5 EB05 29.3 · IC025 +3.8 3/3 methods agree | Labeled adverse reaction exact term | serious n=23 · 100% clinician | not reported in cached trials |
| Anticonvulsant drug level increased | 48 | 43.3 32.5–57.7ROR 43.5 · χ² 1,884 / p <1e-300 | 41.4 EB05 32.5 · IC025 +4.4 3/3 methods agree | Lab value / disease marker | serious n=20 · 90% clinician | not reported in cached trials |
| Partial seizures | 151 | 43.0 36.6–50.5ROR 43.4 · χ² 5,968 / p <1e-300 | 41.5 EB05 36.3 · IC025 +4.9 3/3 methods agree | Likely indication confounding term in indications | serious n=117 | NCT00477295: 4/300 (1.3%) on Zonisamide (serious AE) |
| Dropped head syndrome | 11 | 41.5 22.8–75.5ROR 41.5 · χ² 384 / p 1e-85 | 37.9 EB05 22.6 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious n=11 | not reported in cached trials |
| Oculomucocutaneous syndrome | 12 | 41.5 23.4–73.6ROR 41.5 · χ² 422 / p 5e-94 | 38.1 EB05 23.2 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious n=11 | not reported in cached trials |
| Status epilepticus | 319 | 41.3 37.0–46.2ROR 42.2 · χ² 12,166 / p <1e-300 | 40.1 EB05 36.5 · IC025 +5.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 30.6 · 93% clinician | not reported in cached trials |
| Hyperammonaemic encephalopathy | 48 | 41.1 30.8–54.7ROR 41.2 · χ² 1,785 / p <1e-300 | 39.4 EB05 30.9 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=48 · ♀ 39% (drug 60%) · 100% clinician | not reported in cached trials |
| Therapeutic product effective for unapproved indication | 10 | 40.2 21.4–75.3ROR 40.2 · χ² 334 / p 6e-75 | 36.6 EB05 21.2 · IC025 +2.7 3/3 methods agree | Labeled (related wording) related wording | serious n=9 | not reported in cached trials |
Trial evidence (ClinicalTrials.gov)
✓ Trial adverse-event data found on ClinicalTrials.gov
Largest completed trials with posted results that list Zonisamide as a study intervention. The right-hand column of the signal table shows whether each FAERS term was also recorded in these trials, with a real denominator (2 of 40 signal terms matched).
- NCT00477295 — A Double-blind Study to Compare the Efficacy and Safety of Zonisamide and Carbamazepine as Monotherapy, in New (N=583, PHASE3; 46 AE terms posted; arms: Zonisamide; Carbamazepine)
- NCT00848549 — Assessing The Long-Term Safety And To Explore The Long-Term Efficacy Of Zonisamide As Monotherapy In Newly Dia (N=295, PHASE3; 64 AE terms posted; arms: Zonisamide (Extension Study 314, NCT0084; Carbamazepine (Extension Study 314, NCT0; Zonisamide (Base Study 310, NCT00477295); Carbamazepine (Base Study 310, NCT004772)
Caveats: trial populations, doses and follow-up differ from the reporting population; AE terms are sponsor-coded and matched here by wording; absence from a trial list means the term was not reported above the sponsor's frequency threshold, not that it cannot occur.
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 |
|---|---|---|---|---|---|---|
| Drug ineffective (drug did not work) | 1,693 | 1.8 1.8–1.9ROR 1.9 · χ² 684 / p 5e-151 | 1.8 EB05 1.8 · IC025 +0.8 | Reporting / coding artifact | serious PRR 3.6 | not reported in cached trials |
| Seizure | 1,653 | 20.8 19.9–21.8ROR 23.3 · χ² 30,891 / p <1e-300 | 20.5 EB05 19.7 · IC025 +4.3 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 14.1 | NCT00477295: 4/300 (1.3%) on Zonisamide (serious AE) |
| Off label use (used outside approved label) | 940 | 1.5 1.5–1.6ROR 1.6 · χ² 188 / p 5e-43 | 1.5 EB05 1.5 · IC025 +0.5 | Reporting / coding artifact | serious PRR 2.0 | not reported in cached trials |
| Fatigue (tiredness) | 725 | 1.3 1.2–1.4ROR 1.3 · χ² 62 / p 2e-15 | 1.3 EB05 1.3 · IC025 +0.3 | Labeled adverse reaction exact term | serious PRR 1.2 | not reported in cached trials |
| Somnolence (drowsiness) | 677 | 4.8 4.5–5.2ROR 5.0 · χ² 2,055 / p <1e-300 | 4.8 EB05 4.5 · IC025 +2.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 4.4 | NCT00477295: 17/281 (6.0%) on Zonisamide |
| Convulsion (seizure) | 623 | 15.5 14.3–16.7ROR 16.1 · χ² 8,350 / p <1e-300 | 15.3 EB05 14.3 · IC025 +3.8 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 7.0 | NCT00477295: 1/281 (0.4%) on Zonisamide (serious AE) |
| Nausea | 577 | 1.0 1.0–1.1ROR 1.0 · χ² 1 / p 0.158 | 1.0 EB05 1.0 · IC025 -0.1 PRR-only: not supported by EBGM or IC | Labeled adverse reaction exact term | serious PRR 0.9 | not reported in cached trials |
| Dizziness | 577 | 1.7 1.5–1.8ROR 1.7 · χ² 152 / p 4e-35 | 1.7 EB05 1.5 · IC025 +0.6 | Labeled adverse reaction exact term | serious PRR 1.5 | NCT00477295: 11/281 (3.9%) on Zonisamide |
| Headache | 565 | 1.3 1.2–1.4ROR 1.3 · χ² 37 / p 6e-10 | 1.3 EB05 1.2 · IC025 +0.2 | Labeled adverse reaction exact term | serious PRR 1.2 | NCT00477295: 29/281 (10.3%) on Zonisamide |
| Fall | 516 | 2.2 2.0–2.4ROR 2.3 · χ² 348 / p 7e-78 | 2.2 EB05 2.1 · IC025 +1.0 3/3 methods agree | Not in label — unassessed | serious PRR 1.7 | not reported in cached trials |
| Drug interaction | 479 | 4.3 4.0–4.7ROR 4.4 · χ² 1,222 / p 6e-268 | 4.3 EB05 4.0 · IC025 +1.9 3/3 methods agree | Reporting / coding artifact | serious PRR 3.3 · 92% clinician | not reported in cached trials |
| Condition aggravated | 459 | 2.2 2.0–2.4ROR 2.2 · χ² 292 / p 1e-65 | 2.2 EB05 2.0 · IC025 +1.0 3/3 methods agree | Reporting / coding artifact | serious PRR 2.2 | not reported in cached trials |
| Vomiting | 450 | 1.4 1.2–1.5ROR 1.4 · χ² 45 / p 8e-12 | 1.4 EB05 1.3 · IC025 +0.3 | Labeled adverse reaction exact term | serious PRR 1.2 | not reported in cached trials |
| Diarrhoea (diarrhea) | 421 | 0.9 0.8–1.0ROR 0.9 · χ² 2 / p 0.078 | 0.9 EB05 0.9 · IC025 -0.3 PRR-only: not supported by EBGM or IC | Labeled adverse reaction exact term | serious PRR 0.7 | not reported in cached trials |
| Epilepsy | 404 | 19.1 17.4–21.1ROR 19.6 · χ² 6,836 / p <1e-300 | 18.9 EB05 17.4 · IC025 +4.0 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 14.8 | NCT00477295: 1/300 (0.3%) on Zonisamide (serious AE) |
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.
- Tuberous sclerosis complex — n=27, PRR 499.5
- Postictal psychosis — n=20, PRR 211.4
- Vagal nerve stimulator implantation — n=27, PRR 142.7
- Postictal paralysis — n=21, PRR 135.4
- Congenital aplasia — n=22, PRR 117.2
- Infantile spasms — n=32, PRR 66.8
- Tonic convulsion — n=50, PRR 52.7
- Foetal malformation — n=39, PRR 52.6
- Hyperammonaemic encephalopathy — n=48, PRR 41.1
✓ A hand-written Bradford Hill causality assessment exists for this drug: Zonisamide ↔ Nephrolithiasis.
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 Zonisamide?
In FDA FAERS, the most frequently co-reported reaction terms for Zonisamide are seizure, fatigue, somnolence, convulsion, nausea, dizziness. 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 Zonisamide have an FDA boxed warning?
No. The FDA label retrieved for Zonisamide has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Zonisamide 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 0bc550a7-09a7-75e4-e063-6294a90a9fc1, effective 20241231; matched on
openfda.generic_name.exact:"ZONISAMIDE") - 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, 1,110 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 - ClinicalTrials.gov API v2 (query
ZONISAMIDE, results-bearing studies sorted by enrollment)
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.