Phenobarbital Sodium side effects: what 402 FDA adverse event reports show

Phenobarbital Sodium · 11 reaction terms · 181 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Who reports

402 reports · 97% serious · 61 with death outcome · 51% female

openFDA FAERS counts, all years, deduplication not applied

Used for

A. Sedative B. Anticonvulsant–For the treatment of generalized and partial seizures.

FDA label, Indications and Usage

What it is

DESCRIPTION The barbiturates are nonselective central nervous system (CNS) depressants that are primarily used as sedative-hypnotics. In sub-hypnotic doses, they are also used as anticonvulsants. The barbiturates and their sodium salts are subject to control under the Federal Controlled Substances Act.

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 8 strongest signals

Labeled (related wording) 1Likely indication confounding 1Reporting / coding artifact 1Lab value / disease marker 1Not in label — unassessed 4

What the badges mean

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. 3 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
Status epilepticus	21	97.0 63.9–147.1ROR 102.3 · χ² 1,897 / p <1e-300	89.2 EB05 61.5 · IC025 +4.2 3/3 methods agree	Not in label — unassessed	serious PRR 57.4 · 95% clinician	no trial data cached
Epilepsy	27	46.2 32.1–66.5ROR 49.4 · χ² 1,150 / p 3e-252	44.8 EB05 32.3 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious PRR 27.5	no trial data cached
Neutrophil count increased	8	40.6 20.5–80.7ROR 41.4 · χ² 271 / p 4e-61	37.2 EB05 20.1 · IC025 +2.4 3/3 methods agree	Lab value / disease marker	serious PRR 26.4	no trial data cached
Pallor	18	34.4 21.9–54.1ROR 36.0 · χ² 552 / p 3e-122	33.3 EB05 22.3 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious PRR 26.6	no trial data cached
Drug resistance	15	30.5 18.5–50.1ROR 31.6 · χ² 399 / p 5e-89	29.4 EB05 18.9 · IC025 +3.1 3/3 methods agree	Reporting / coding artifact	serious PRR 20.3	no trial data cached
Seizure	67	30.5 24.5–37.9ROR 36.4 · χ² 1,889 / p <1e-300	30.2 EB05 24.6 · IC025 +4.2 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 19.1	no trial data cached
Drug reaction with eosinophilia and systemic symptoms	9	18.4 9.6–35.1ROR 18.8 · χ² 131 / p 1e-30	16.8 EB05 8.1 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 10.9	no trial data cached
Abortion spontaneous	6	7.8 3.5–17.2ROR 7.9 · χ² 29 / p 4e-8	5.3 EB05 2.6 · IC025 +0.9 3/3 methods agree	Labeled (related wording) related wording	serious PRR 4.6	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
Seizure	67	30.5 24.5–37.9ROR 36.4 · χ² 1,889 / p <1e-300	30.2 EB05 24.6 · IC025 +4.2 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 19.1	no trial data cached
Epilepsy	27	46.2 32.1–66.5ROR 49.4 · χ² 1,150 / p 3e-252	44.8 EB05 32.3 · IC025 +4.0 3/3 methods agree	Not in label — unassessed	serious PRR 27.5	no trial data cached
Status epilepticus	21	97.0 63.9–147.1ROR 102.3 · χ² 1,897 / p <1e-300	89.2 EB05 61.5 · IC025 +4.2 3/3 methods agree	Not in label — unassessed	serious PRR 57.4 · 95% clinician	no trial data cached
Pallor	18	34.4 21.9–54.1ROR 36.0 · χ² 552 / p 3e-122	33.3 EB05 22.3 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious PRR 26.6	no trial data cached
Drug resistance	15	30.5 18.5–50.1ROR 31.6 · χ² 399 / p 5e-89	29.4 EB05 18.9 · IC025 +3.1 3/3 methods agree	Reporting / coding artifact	serious PRR 20.3	no trial data cached
Drug reaction with eosinophilia and systemic symptoms	9	18.4 9.6–35.1ROR 18.8 · χ² 131 / p 1e-30	16.8 EB05 8.1 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 10.9	no trial data cached
Neutrophil count increased	8	40.6 20.5–80.7ROR 41.4 · χ² 271 / p 4e-61	37.2 EB05 20.1 · IC025 +2.4 3/3 methods agree	Lab value / disease marker	serious PRR 26.4	no trial data cached
Abortion spontaneous	6	7.8 3.5–17.2ROR 7.9 · χ² 29 / p 4e-8	5.3 EB05 2.6 · IC025 +0.9 3/3 methods agree	Labeled (related wording) related wording	serious PRR 4.6	no trial data cached
Product complaint	4	8.4 3.2–22.2ROR 8.4 · χ² 19 / p 6e-6	4.9 EB05 2.0 · IC025 +0.4 3/3 methods agree	Reporting / coding artifact	serious n=4	no trial data cached
Respiratory depression	3	12.8 4.1–39.4ROR 12.9 · χ² 22 / p 1e-6	6.5 EB05 2.0 · IC025 +0.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.8	no trial data cached
Drug level decreased	3	15.3 5.0–47.3ROR 15.4 · χ² 27 / p 1e-7	8.0 EB05 2.2 · IC025 +0.3 3/3 methods agree	Reporting / coding artifact	serious PRR 11.2	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.

Status epilepticus — n=21, PRR 97.0
Epilepsy — n=27, PRR 46.2

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 Phenobarbital?

In FDA FAERS, the most frequently co-reported reaction terms for Phenobarbital are seizure, epilepsy, status epilepticus, pallor, drug reaction with eosinophilia and systemic symptoms, neutrophil count increased. 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 Phenobarbital have an FDA boxed warning?

No. The FDA label retrieved for Phenobarbital has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Phenobarbital 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 057992c1-29a0-4229-9c30-d787cb632eac, effective 20250922; matched on openfda.generic_name.exact:"PHENOBARBITAL")
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, 11 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.