Glycerol Phenylbutyrate side effects: what 1,358 FDA adverse event reports show

Glycerol Phenylbutyrate · 20 reaction terms · 296 drug–reaction co-reports · data 2026-09-14

Drug class

Nitrogen-binding agent

FDA label, Indications wording

Who reports

1,358 reports · 60% serious · 65 with death outcome · 58% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Glycerol phenylbutyrate oral liquid is indicated for use as a nitrogen-binding agent for chronic management of patients with urea cycle disorders (UCDs) who cannot be managed by dietary protein restriction and/or amino acid supplementation alone. Glyce.

FDA label, Indications and Usage

What it is

Glycerol phenylbutyrate oral liquid is a clear, colorless to pale yellow oral liquid. It is insoluble in water and most organic solvents, and it is soluble in dimethylsulfoxide (DMSO) and greater than 65% acetonitrile. Glycerol phenylbutyrate is a nitrogen-binding agent.

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 16 strongest signals

Labeled adverse reaction 5Labeled (related wording) 1Reporting / coding artifact 3Not in label — unassessed 7

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.
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. 4 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
Gastroenteritis viral	27	23.1 15.9–33.5ROR 23.5 · χ² 547 / p 2e-121	22.7 EB05 16.4 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious PRR 38.9 · 81% consumer	no trial data cached
Hypophagia	28	17.1 11.8–24.6ROR 17.4 · χ² 407 / p 7e-91	16.8 EB05 12.0 · IC025 +3.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 16.3	no trial data cached
Lethargy	40	10.7 7.9–14.6ROR 11.0 · χ² 345 / p 3e-77	10.3 EB05 7.7 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 11.1	no trial data cached
Pharyngitis streptococcal	7	10.0 4.8–20.9ROR 10.0 · χ² 48 / p 2e-12	7.2 EB05 3.4 · IC025 +1.3 3/3 methods agree	Not in label — unassessed	serious n=5	no trial data cached
Viral infection	21	9.8 6.4–14.9ROR 9.9 · χ² 157 / p 3e-36	8.8 EB05 5.8 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious PRR 11.9	no trial data cached
Mental status changes	17	9.4 5.9–15.2ROR 9.6 · χ² 120 / p 3e-28	8.2 EB05 5.2 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 9.5	no trial data cached
Retching	12	8.7 5.0–15.3ROR 8.8 · χ² 74 / p 3e-18	7.1 EB05 4.1 · IC025 +1.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.9	no trial data cached
Brain oedema	7	8.6 4.1–17.9ROR 8.6 · χ² 40 / p 2e-10	6.1 EB05 3.0 · IC025 +1.2 3/3 methods agree	Not in label — unassessed	serious PRR 8.3	no trial data cached
Metabolic acidosis	16	7.8 4.8–12.7ROR 7.9 · χ² 88 / p 3e-21	6.6 EB05 4.2 · IC025 +1.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.5	no trial data cached
Product taste abnormal	6	6.9 3.1–15.3ROR 6.9 · χ² 25 / p 3e-7	4.8 EB05 2.4 · IC025 +0.8 3/3 methods agree	Reporting / coding artifact	serious n=1	no trial data cached
Irritability	25	6.4 4.3–9.5ROR 6.5 · χ² 109 / p 8e-26	5.8 EB05 4.1 · IC025 +1.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.5	no trial data cached
Abnormal behaviour	15	5.8 3.5–9.6ROR 5.9 · χ² 55 / p 6e-14	5.0 EB05 3.2 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 6.2	no trial data cached
Increased appetite	7	5.8 2.7–12.0ROR 5.8 · χ² 23 / p 8e-7	4.3 EB05 2.3 · IC025 +0.8 3/3 methods agree	Labeled (related wording) related wording	serious PRR 6.1	no trial data cached
Aggression	12	3.7 2.1–6.5ROR 3.7 · χ² 21 / p 2e-6	3.3 EB05 2.0 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	serious PRR 1.8	no trial data cached
Drug dose omission	27	2.5 1.7–3.6ROR 2.5 · χ² 23 / p 9e-7	2.4 EB05 1.8 · IC025 +0.6	Reporting / coding artifact	serious PRR 6.1	no trial data cached
Accidental exposure to product	14	2.2 1.3–3.6ROR 2.2 · χ² 8 / p 0.003	2.1 EB05 1.3 · IC025 +0.2	Reporting / coding artifact	serious PRR 3.4	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
Lethargy	40	10.7 7.9–14.6ROR 11.0 · χ² 345 / p 3e-77	10.3 EB05 7.7 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 11.1	no trial data cached
Hypophagia	28	17.1 11.8–24.6ROR 17.4 · χ² 407 / p 7e-91	16.8 EB05 12.0 · IC025 +3.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 16.3	no trial data cached
Drug dose omission	27	2.5 1.7–3.6ROR 2.5 · χ² 23 / p 9e-7	2.4 EB05 1.8 · IC025 +0.6	Reporting / coding artifact	serious PRR 6.1	no trial data cached
Gastroenteritis viral	27	23.1 15.9–33.5ROR 23.5 · χ² 547 / p 2e-121	22.7 EB05 16.4 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious PRR 38.9 · 81% consumer	no trial data cached
Irritability	25	6.4 4.3–9.5ROR 6.5 · χ² 109 / p 8e-26	5.8 EB05 4.1 · IC025 +1.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.5	no trial data cached
Viral infection	21	9.8 6.4–14.9ROR 9.9 · χ² 157 / p 3e-36	8.8 EB05 5.8 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious PRR 11.9	no trial data cached
Mental status changes	17	9.4 5.9–15.2ROR 9.6 · χ² 120 / p 3e-28	8.2 EB05 5.2 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 9.5	no trial data cached
Metabolic acidosis	16	7.8 4.8–12.7ROR 7.9 · χ² 88 / p 3e-21	6.6 EB05 4.2 · IC025 +1.9 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.5	no trial data cached
Abnormal behaviour	15	5.8 3.5–9.6ROR 5.9 · χ² 55 / p 6e-14	5.0 EB05 3.2 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 6.2	no trial data cached
Accidental exposure to product	14	2.2 1.3–3.6ROR 2.2 · χ² 8 / p 0.003	2.1 EB05 1.3 · IC025 +0.2	Reporting / coding artifact	serious PRR 3.4	no trial data cached
Aggression	12	3.7 2.1–6.5ROR 3.7 · χ² 21 / p 2e-6	3.3 EB05 2.0 · IC025 +0.8 3/3 methods agree	Not in label — unassessed	serious PRR 1.8	no trial data cached
Retching	12	8.7 5.0–15.3ROR 8.8 · χ² 74 / p 3e-18	7.1 EB05 4.1 · IC025 +1.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.9	no trial data cached
Increased appetite	7	5.8 2.7–12.0ROR 5.8 · χ² 23 / p 8e-7	4.3 EB05 2.3 · IC025 +0.8 3/3 methods agree	Labeled (related wording) related wording	serious PRR 6.1	no trial data cached
Brain oedema	7	8.6 4.1–17.9ROR 8.6 · χ² 40 / p 2e-10	6.1 EB05 3.0 · IC025 +1.2 3/3 methods agree	Not in label — unassessed	serious PRR 8.3	no trial data cached
Pharyngitis streptococcal	7	10.0 4.8–20.9ROR 10.0 · χ² 48 / p 2e-12	7.2 EB05 3.4 · IC025 +1.3 3/3 methods agree	Not in label — unassessed	serious n=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.

Gastroenteritis viral — n=27, PRR 23.1
Viral infection — n=21, PRR 9.8

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 Glycerol Phenylbutyrate?

In FDA FAERS, the most frequently co-reported reaction terms for Glycerol Phenylbutyrate are lethargy, hypophagia, gastroenteritis viral, irritability, viral infection, mental status changes. 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 Glycerol Phenylbutyrate have an FDA boxed warning?

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

Do FAERS signals prove that Glycerol Phenylbutyrate 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 28bb5ec0-a99f-4774-b8a8-b6c229b89ba5, effective 20250301; matched on openfda.generic_name.exact:"GLYCEROL PHENYLBUTYRATE")
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, 20 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.