Drug · FAERS side-effect profile with label screen
Primidone side effects: what 10,121 FDA adverse event reports show
Who reports
10,121 reports · 66% serious · 874 with death outcome · 60% female
openFDA FAERS counts, all years, deduplication not applied
Used for
Primidone, used alone or concomitantly with other anticonvulsants, is indicated in the control of grand mal, psychomotor, and focal epileptic seizures. It may control grand mal seizures refractory to other anticonvulsant therapy.
FDA label, Indications and Usage
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 3Labeled (related wording) 1Likely indication confounding 3Reporting / coding artifact 2Lab value / disease marker 5Not in label — unassessed 26
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. 1,061 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 |
|---|---|---|---|---|---|---|
| Growth hormone-producing pituitary tumour | 15 | 1,802.0 900.2–3,607.3ROR 1,804.7 · χ² 13,403 / p <1e-300 | 430.3 EB05 276.8 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Shunt malfunction | 15 | 114.7 68.2–192.9ROR 114.9 · χ² 1,495 / p <1e-300 | 95.8 EB05 61.6 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Parkinsonian rest tremor | 10 | 114.1 60.4–215.6ROR 114.2 · χ² 957 / p 2e-210 | 90.1 EB05 52.3 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=9 | no trial data cached |
| Essential tremor | 58 | 113.5 87.2–147.7ROR 114.1 · χ² 6,019 / p <1e-300 | 103.9 EB05 83.4 · IC025 +5.4 3/3 methods agree | Not in label — unassessed | serious n=37 | no trial data cached |
| Gastric hypomotility | 15 | 107.9 64.2–181.2ROR 108.0 · χ² 1,409 / p <1e-300 | 91.0 EB05 58.5 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Lennox-gastaut syndrome | 11 | 106.5 58.1–195.1ROR 106.6 · χ² 994 / p 2e-218 | 86.5 EB05 51.6 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial data cached |
| Viral diarrhoea | 15 | 94.8 56.5–159.1ROR 95.0 · χ² 1,243 / p 2e-272 | 81.6 EB05 52.5 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Shunt occlusion | 15 | 63.2 37.8–105.6ROR 63.3 · χ² 831 / p 5e-183 | 57.1 EB05 36.7 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Blood growth hormone increased | 15 | 56.4 33.8–94.2ROR 56.5 · χ² 742 / p 1e-163 | 51.5 EB05 33.2 · IC025 +3.5 3/3 methods agree | Lab value / disease marker | serious n=15 | no trial data cached |
| Cerebellar atrophy | 20 | 47.9 30.7–74.6ROR 48.0 · χ² 852 / p 1e-187 | 44.9 EB05 30.7 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=20 | no trial data cached |
| Anticonvulsant drug level above therapeutic | 14 | 45.4 26.7–77.0ROR 45.4 · χ² 552 / p 2e-122 | 42.1 EB05 26.6 · IC025 +3.2 3/3 methods agree | Lab value / disease marker | serious n=14 | no trial data cached |
| Anticonvulsant drug level increased | 27 | 34.9 23.9–51.1ROR 35.0 · χ² 842 / p 2e-185 | 33.6 EB05 24.3 · IC025 +3.8 3/3 methods agree | Lab value / disease marker | serious n=27 | no trial data cached |
| Anticonvulsant drug level decreased | 22 | 32.4 21.3–49.3ROR 32.5 · χ² 628 / p 6e-139 | 31.1 EB05 21.7 · IC025 +3.5 3/3 methods agree | Lab value / disease marker | serious n=18 | no trial data cached |
| Myoclonic epilepsy | 22 | 31.4 20.6–47.8ROR 31.4 · χ² 608 / p 2e-134 | 30.2 EB05 21.0 · IC025 +3.5 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=22 · 100% clinician | no trial data cached |
| Ingrown hair | 10 | 30.9 16.5–57.6ROR 30.9 · χ² 256 / p 7e-58 | 28.8 EB05 16.6 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Focal dyscognitive seizures | 14 | 25.7 15.2–43.5ROR 25.7 · χ² 304 / p 2e-68 | 24.6 EB05 15.4 · IC025 +2.9 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=13 | no trial data cached |
| Alcohol withdrawal syndrome | 10 | 23.9 12.8–44.5ROR 23.9 · χ² 194 / p 2e-44 | 22.4 EB05 12.5 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Multiple-drug resistance | 33 | 22.3 15.8–31.4ROR 22.4 · χ² 644 / p 3e-142 | 21.8 EB05 16.2 · IC025 +3.5 3/3 methods agree | Reporting / coding artifact | serious n=30 · ♀ 35% (drug 60%) · 100% clinician | no trial data cached |
| Petit mal epilepsy | 54 | 22.2 17.0–29.0ROR 22.3 · χ² 1,062 / p 4e-233 | 21.8 EB05 17.4 · IC025 +3.8 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=53 | no trial data cached |
| Insulin-like growth factor increased | 15 | 21.9 13.2–36.4ROR 21.9 · χ² 276 / p 3e-62 | 21.0 EB05 13.3 · IC025 +2.8 3/3 methods agree | Lab value / disease marker | serious n=15 | no trial data cached |
| Chronic kidney disease-mineral and bone disorder | 11 | 21.4 11.8–38.7ROR 21.4 · χ² 192 / p 7e-44 | 20.2 EB05 11.4 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial data cached |
| Hemianopia | 10 | 20.9 11.2–39.0ROR 20.9 · χ² 169 / p 7e-39 | 19.5 EB05 10.5 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Head titubation | 12 | 18.1 10.3–32.0ROR 18.1 · χ² 176 / p 2e-40 | 17.0 EB05 9.6 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=8 | no trial data cached |
| Drug withdrawal convulsions | 15 | 17.5 10.6–29.1ROR 17.6 · χ² 216 / p 4e-49 | 16.7 EB05 10.2 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Aura | 15 | 16.8 10.1–28.0ROR 16.8 · χ² 206 / p 5e-47 | 16.0 EB05 9.7 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=9 | no trial data cached |
| Ataxia | 95 | 16.6 13.6–20.3ROR 16.8 · χ² 1,370 / p 4e-300 | 16.4 EB05 13.8 · IC025 +3.6 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 15.2 · 93% clinician | no trial data cached |
| Lip haemorrhage | 10 | 16.4 8.8–30.5ROR 16.4 · χ² 128 / p 5e-30 | 14.7 EB05 7.4 · IC025 +2.2 3/3 methods agree | Labeled (related wording) related wording | serious n=9 | no trial data cached |
| Obstructive sleep apnoea syndrome | 10 | 14.9 8.0–27.8ROR 14.9 · χ² 116 / p 3e-27 | 13.1 EB05 6.5 · IC025 +2.1 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Strabismus | 20 | 14.2 9.1–22.0ROR 14.2 · χ² 230 / p 3e-52 | 13.4 EB05 8.7 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious n=20 | no trial data cached |
| Nystagmus | 34 | 13.3 9.5–18.7ROR 13.4 · χ² 374 / p 1e-83 | 12.9 EB05 9.4 · IC025 +2.9 3/3 methods agree | Labeled adverse reaction exact term | serious n=33 | no trial data cached |
| Hyperparathyroidism secondary | 16 | 13.2 8.1–21.5ROR 13.2 · χ² 167 / p 2e-38 | 12.1 EB05 7.2 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious n=16 | no trial data cached |
| Inhibitory drug interaction | 10 | 13.1 7.0–24.4ROR 13.1 · χ² 99 / p 1e-23 | 11.1 EB05 5.6 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious n=9 | no trial data cached |
| Breath odour | 15 | 12.8 7.7–21.2ROR 12.8 · χ² 150 / p 7e-35 | 11.5 EB05 6.8 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Infrequent bowel movements | 15 | 12.5 7.5–20.8ROR 12.5 · χ² 147 / p 5e-34 | 11.2 EB05 6.6 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious n=15 | no trial data cached |
| Pathological gambling | 10 | 12.4 6.6–23.0ROR 12.4 · χ² 93 / p 3e-22 | 10.3 EB05 5.2 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | – | no trial data cached |
| Hyperammonaemic encephalopathy | 10 | 12.1 6.5–22.6ROR 12.2 · χ² 91 / p 7e-22 | 10.0 EB05 5.1 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Eye contusion | 11 | 10.9 6.0–19.6ROR 10.9 · χ² 88 / p 3e-21 | 8.9 EB05 4.8 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious n=9 | no trial data cached |
| Grand mal convulsion | 48 | 10.7 8.0–14.1ROR 10.7 · χ² 409 / p 4e-91 | 10.2 EB05 7.9 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 9.5 | no trial data cached |
| Status epilepticus | 57 | 10.5 8.1–13.6ROR 10.5 · χ² 477 / p 5e-106 | 10.1 EB05 8.0 · IC025 +2.8 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 9.2 · ♀ 34% (drug 60%) · 93% clinician | no trial data cached |
| Therapeutic response unexpected with drug substitution | 21 | 10.4 6.8–15.9ROR 10.4 · χ² 168 / p 1e-38 | 9.4 EB05 6.2 · IC025 +2.4 3/3 methods agree | Reporting / coding artifact | serious n=14 | 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 |
|---|---|---|---|---|---|---|
| Drug ineffective (drug did not work) | 837 | 1.3 1.2–1.4ROR 1.3 · χ² 68 / p 1e-16 | 1.3 EB05 1.2 · IC025 +0.3 | Reporting / coding artifact | serious PRR 2.0 | no trial data cached |
| Fall | 670 | 4.2 3.9–4.5ROR 4.4 · χ² 1,640 / p <1e-300 | 4.2 EB05 3.9 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 3.8 | no trial data cached |
| Fatigue (tiredness) | 645 | 1.7 1.6–1.9ROR 1.8 · χ² 201 / p 7e-46 | 1.7 EB05 1.6 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 1.7 | no trial data cached |
| Tremor (shaking) | 585 | 7.3 6.8–7.9ROR 7.7 · χ² 3,193 / p <1e-300 | 7.3 EB05 6.8 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 6.5 | no trial data cached |
| Off label use (used outside approved label) | 502 | 1.2 1.1–1.3ROR 1.2 · χ² 17 / p 2e-5 | 1.2 EB05 1.1 · IC025 +0.1 | Reporting / coding artifact | serious PRR 1.2 | no trial data cached |
| Diarrhoea (diarrhea) | 498 | 1.6 1.5–1.7ROR 1.6 · χ² 116 / p 2e-27 | 1.6 EB05 1.5 · IC025 +0.5 | Not in label — unassessed | serious PRR 1.5 | no trial data cached |
| Dizziness | 498 | 2.1 1.9–2.3ROR 2.1 · χ² 282 / p 2e-63 | 2.1 EB05 1.9 · IC025 +0.9 | Not in label — unassessed | serious PRR 2.2 | no trial data cached |
| Nausea | 471 | 1.2 1.1–1.4ROR 1.2 · χ² 22 / p 1e-6 | 1.2 EB05 1.1 · IC025 +0.2 | Labeled adverse reaction exact term | serious PRR 1.4 | no trial data cached |
| Drug interaction | 406 | 5.3 4.8–5.8ROR 5.5 · χ² 1,423 / p <1e-300 | 5.3 EB05 4.9 · IC025 +2.2 3/3 methods agree | Reporting / coding artifact | serious PRR 4.1 | no trial data cached |
| Headache | 397 | 1.3 1.2–1.4ROR 1.3 · χ² 30 / p 2e-8 | 1.3 EB05 1.2 · IC025 +0.2 | Not in label — unassessed | serious PRR 1.5 | no trial data cached |
| Somnolence (drowsiness) | 390 | 4.0 3.6–4.4ROR 4.1 · χ² 890 / p 9e-196 | 4.0 EB05 3.7 · IC025 +1.8 3/3 methods agree | Labeled (related wording) related wording | serious PRR 4.2 | no trial data cached |
| Dyspnoea (shortness of breath) | 362 | 1.3 1.2–1.5ROR 1.3 · χ² 29 / p 3e-8 | 1.3 EB05 1.2 · IC025 +0.2 | Not in label — unassessed | serious PRR 1.1 | no trial data cached |
| Asthenia (weakness) | 361 | 2.0 1.8–2.2ROR 2.0 · χ² 180 / p 3e-41 | 2.0 EB05 1.8 · IC025 +0.8 | Not in label — unassessed | serious PRR 1.9 | no trial data cached |
| Weight decreased (weight loss) | 336 | 2.5 2.2–2.8ROR 2.5 · χ² 303 / p 3e-68 | 2.5 EB05 2.3 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 2.7 | no trial data cached |
| Pain | 328 | 1.1 1.0–1.2ROR 1.1 · χ² 3 / p 0.037 | 1.1 EB05 1.0 · IC025 -0.0 PRR-only: not supported by EBGM or IC | Not in label — unassessed | serious PRR 1.2 | 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.
- Essential tremor — n=58, PRR 113.5
- Cerebellar atrophy — n=20, PRR 47.9
- Strabismus — n=20, PRR 14.2
- Grand mal convulsion — n=48, PRR 10.7
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 Primidone?
In FDA FAERS, the most frequently co-reported reaction terms for Primidone are fall, fatigue, tremor, diarrhoea, dizziness, nausea. 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 Primidone have an FDA boxed warning?
No. The FDA label retrieved for Primidone has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Primidone 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 0193c0a4-f593-609c-e063-6294a90aaa68, effective 20250610; matched on
openfda.generic_name.exact:"PRIMIDONE") - 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, 1,101 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.