Fenfluramine side effects: what 4,663 FDA adverse event reports show

Fenfluramine · Fintepla · 156 reaction terms · 10,993 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Brand names

Fintepla

openFDA label

Who reports

4,663 reports · 81% serious · 114 with death outcome · 49% female

openFDA FAERS counts, all years, deduplication not applied

Used for

FINTEPLA is indicated for the treatment of seizures associated with Dravet syndrome (DS) and Lennox-Gastaut syndrome (LGS) in patients 2 years of age and older. FINTEPLA is indicated for the treatment of seizures associated with Dravet syndrome and Lennox-Gastaut syndrome in patients 2 years of age and older. ( 1 )

FDA label, Indications and Usage

What it is

FINTEPLA oral solution contains 2.2 mg/mL fenfluramine, equivalent to 2.5 mg/mL of the hydrochloride salt. The active ingredient, fenfluramine hydrochloride, is designated chemically as N-ethyl-α- methyl-3-(trifluoromethyl)phenethylamine hydrochloride.

FDA label, Description section

Boxed warning

VALVULAR HEART DISEASE and PULMONARY ARTERIAL HYPERTENSION FINTEPLA can cause valvular heart disease and pulmonary arterial hypertension [see Warnings and Precautions (5.1) ]. Echocardiogram assessments are required before, during, and after treatment with FINTEPLA.

FDA 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 — boxed warning 7Labeled adverse reaction 10Labeled (related wording) 3Likely indication confounding 1Reporting / coding artifact 1Lab value / disease marker 1Not in label — unassessed 17

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.
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. 116 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
Mitral valve incompetence	363	148.9 134.7–164.7ROR 161.4 · χ² 51,489 / p <1e-300	143.0 EB05 131.1 · IC025 +6.7 3/3 methods agree	Not in label — unassessed	serious PRR 102.1	no trial data cached
Seizure	2,042	81.4 78.8–84.1ROR 144.0 · χ² 160,052 / p <1e-300	79.9 EB05 77.0 · IC025 +6.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 54.3 · 75% consumer	no trial data cached
Generalised tonic-clonic seizure	258	72.0 63.9–81.1ROR 76.1 · χ² 17,715 / p <1e-300	70.5 EB05 63.6 · IC025 +5.8 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 46.8	no trial data cached
Status epilepticus	110	44.1 36.6–53.1ROR 45.1 · χ² 4,548 / p <1e-300	43.4 EB05 37.0 · IC025 +4.9 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 30.3	no trial data cached
Epilepsy	119	17.6 14.7–21.0ROR 18.0 · χ² 1,841 / p <1e-300	17.5 EB05 15.0 · IC025 +3.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 12.5	no trial data cached
Hypersomnia	106	16.7 13.8–20.2ROR 17.1 · χ² 1,545 / p <1e-300	16.6 EB05 14.1 · IC025 +3.6 3/3 methods agree	Not in label — unassessed	serious PRR 20.4 · 79% consumer	no trial data cached
Pericardial effusion	74	14.5 11.6–18.2ROR 14.7 · χ² 914 / p 4e-201	14.3 EB05 11.8 · IC025 +3.3 3/3 methods agree	Not in label — unassessed	serious PRR 10.4	no trial data cached
Aggression	155	13.9 11.9–16.3ROR 14.4 · χ² 1,846 / p <1e-300	13.8 EB05 12.1 · IC025 +3.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.2 · 74% consumer	no trial data cached
Gastroenteritis viral	54	13.4 10.3–17.5ROR 13.6 · χ² 608 / p 2e-134	13.2 EB05 10.4 · IC025 +3.1 3/3 methods agree	Labeled (related wording) related wording	serious PRR 17.5 · 83% consumer	no trial data cached
Pharyngitis streptococcal	32	13.3 9.4–18.8ROR 13.4 · χ² 352 / p 1e-78	12.9 EB05 9.3 · IC025 +2.9 3/3 methods agree	Not in label — unassessed	serious n=32 · 88% consumer	no trial data cached
Lethargy	160	12.5 10.8–14.6ROR 12.9 · χ² 1,687 / p <1e-300	12.4 EB05 10.9 · IC025 +3.3 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 11.6 · 79% consumer	no trial data cached
Abnormal behaviour	92	10.4 8.5–12.7ROR 10.6 · χ² 771 / p 6e-170	10.2 EB05 8.5 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 7.0 · 80% consumer	no trial data cached
Decreased appetite (loss of appetite)	529	10.3 9.5–11.1ROR 11.5 · χ² 4,465 / p <1e-300	10.2 EB05 9.5 · IC025 +3.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 8.9 · 74% consumer	no trial data cached
Prescribed overdose	44	10.2 7.6–13.7ROR 10.3 · χ² 357 / p 6e-80	9.8 EB05 7.4 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 8.2	no trial data cached
Myoclonus	27	10.2 7.0–14.9ROR 10.3 · χ² 214 / p 7e-49	9.4 EB05 6.6 · IC025 +2.5 3/3 methods agree	Not in label — unassessed	serious PRR 7.1	no trial data cached
Somnolence (drowsiness)	454	10.2 9.3–11.1ROR 11.2 · χ² 3,772 / p <1e-300	10.1 EB05 9.3 · IC025 +3.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 10.4 · 71% consumer	no trial data cached
Psychomotor hyperactivity	36	9.7 7.0–13.5ROR 9.8 · χ² 273 / p 1e-61	9.1 EB05 6.7 · IC025 +2.6 3/3 methods agree	Not in label — unassessed	serious PRR 8.9 · 78% consumer	no trial data cached
Sedation	55	9.5 7.3–12.4ROR 9.6 · χ² 409 / p 2e-91	9.1 EB05 7.2 · IC025 +2.7 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 8.3	no trial data cached
Viral infection	70	9.5 7.5–12.0ROR 9.6 · χ² 522 / p 7e-116	9.2 EB05 7.4 · IC025 +2.8 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 8.9 · 75% consumer	no trial data cached
Pulmonary arterial hypertension	29	9.0 6.2–12.9ROR 9.0 · χ² 197 / p 5e-45	8.2 EB05 5.9 · IC025 +2.4 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 6.6	no trial data cached
Hypotonia	19	8.5 5.4–13.4ROR 8.6 · χ² 119 / p 6e-28	7.4 EB05 4.9 · IC025 +2.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 5.8	no trial data cached
Irritability	112	8.4 7.0–10.1ROR 8.6 · χ² 720 / p 6e-159	8.2 EB05 7.0 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 7.9 · 76% consumer	no trial data cached
Ear infection	49	8.3 6.3–11.0ROR 8.4 · χ² 308 / p 4e-69	7.9 EB05 6.1 · IC025 +2.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 9.7 · 78% consumer	no trial data cached
Muscle twitching	42	8.2 6.1–11.1ROR 8.2 · χ² 257 / p 3e-58	7.7 EB05 5.9 · IC025 +2.4 3/3 methods agree	Not in label — unassessed	serious PRR 7.6 · 81% consumer	no trial data cached
Agitation	133	8.1 6.9–9.6ROR 8.3 · χ² 826 / p 7e-182	8.0 EB05 6.9 · IC025 +2.7 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.8	no trial data cached
Prescribed underdose	36	8.1 5.9–11.3ROR 8.2 · χ² 218 / p 1e-49	7.5 EB05 5.6 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious PRR 9.6 · 100% clinician	no trial data cached
Pulmonary hypertension	34	7.3 5.2–10.2ROR 7.4 · χ² 179 / p 4e-41	6.8 EB05 5.0 · IC025 +2.2 3/3 methods agree	Labeled (related wording) related wording	serious PRR 5.3	no trial data cached
Seasonal allergy	22	7.0 4.6–10.6ROR 7.0 · χ² 107 / p 2e-25	6.2 EB05 4.3 · IC025 +1.9 3/3 methods agree	Not in label — unassessed	serious n=21 · 82% consumer	no trial data cached
Hospitalisation	236	7.0 6.2–7.9ROR 7.3 · χ² 1,208 / p 7e-265	6.9 EB05 6.2 · IC025 +2.6 3/3 methods agree	Reporting / coding artifact	serious PRR 5.1	no trial data cached
Weight decreased (weight loss)	431	7.0 6.4–7.6ROR 7.6 · χ² 2,216 / p <1e-300	6.9 EB05 6.4 · IC025 +2.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.6	no trial data cached
Crying	56	6.9 5.3–9.0ROR 7.0 · χ² 277 / p 2e-62	6.6 EB05 5.2 · IC025 +2.3 3/3 methods agree	Not in label — unassessed	serious PRR 7.0 · 77% consumer	no trial data cached
Head injury	47	6.7 5.0–8.9ROR 6.8 · χ² 222 / p 2e-50	6.3 EB05 4.9 · IC025 +2.2 3/3 methods agree	Not in label — unassessed	serious PRR 5.1 · 72% consumer	no trial data cached
Anger	49	6.5 4.9–8.6ROR 6.5 · χ² 222 / p 1e-50	6.1 EB05 4.8 · IC025 +2.1 3/3 methods agree	Not in label — unassessed	serious PRR 6.7 · 81% consumer	no trial data cached
Aspiration	15	6.2 3.8–10.3ROR 6.2 · χ² 61 / p 3e-15	5.3 EB05 3.4 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 4.6	no trial data cached
Increased appetite	26	6.2 4.2–9.1ROR 6.3 · χ² 109 / p 9e-26	5.6 EB05 4.0 · IC025 +1.8 3/3 methods agree	Labeled (related wording) related wording	serious PRR 8.8 · 77% consumer	no trial data cached
Secretion discharge	16	5.8 3.6–9.5ROR 5.8 · χ² 59 / p 7e-15	5.0 EB05 3.3 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 6.8	no trial data cached
Ataxia	15	5.7 3.4–9.4ROR 5.7 · χ² 53 / p 2e-13	4.9 EB05 3.1 · IC025 +1.4 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.8	no trial data cached
Mood altered	34	5.6 4.0–7.9ROR 5.7 · χ² 125 / p 3e-29	5.2 EB05 3.9 · IC025 +1.8 3/3 methods agree	Not in label — unassessed	serious PRR 6.5 · 79% consumer	no trial data cached
Ejection fraction decreased	19	5.5 3.5–8.6ROR 5.5 · χ² 65 / p 3e-16	4.9 EB05 3.3 · IC025 +1.5 3/3 methods agree	Lab value / disease marker	serious PRR 3.6	no trial data cached
Salivary hypersecretion	12	5.4 3.1–9.5ROR 5.4 · χ² 39 / p 2e-10	4.5 EB05 2.8 · IC025 +1.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 4.8	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	2,042	81.4 78.8–84.1ROR 144.0 · χ² 160,052 / p <1e-300	79.9 EB05 77.0 · IC025 +6.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 54.3 · 75% consumer	no trial data cached
Drug ineffective (drug did not work)	710	2.4 2.3–2.6ROR 2.7 · χ² 632 / p 9e-140	2.4 EB05 2.3 · IC025 +1.2 3/3 methods agree	Reporting / coding artifact	serious PRR 4.3	no trial data cached
Off label use (used outside approved label)	533	2.8 2.5–3.0ROR 3.0 · χ² 622 / p 1e-137	2.8 EB05 2.6 · IC025 +1.3 3/3 methods agree	Reporting / coding artifact	serious PRR 3.2	no trial data cached
Decreased appetite (loss of appetite)	529	10.3 9.5–11.1ROR 11.5 · χ² 4,465 / p <1e-300	10.2 EB05 9.5 · IC025 +3.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 8.9 · 74% consumer	no trial data cached
Somnolence (drowsiness)	454	10.2 9.3–11.1ROR 11.2 · χ² 3,772 / p <1e-300	10.1 EB05 9.3 · IC025 +3.2 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 10.4 · 71% consumer	no trial data cached
Weight decreased (weight loss)	431	7.0 6.4–7.6ROR 7.6 · χ² 2,216 / p <1e-300	6.9 EB05 6.4 · IC025 +2.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 6.6	no trial data cached
Mitral valve incompetence	363	148.9 134.7–164.7ROR 161.4 · χ² 51,489 / p <1e-300	143.0 EB05 131.1 · IC025 +6.7 3/3 methods agree	Not in label — unassessed	serious PRR 102.1	no trial data cached
Generalised tonic-clonic seizure	258	72.0 63.9–81.1ROR 76.1 · χ² 17,715 / p <1e-300	70.5 EB05 63.6 · IC025 +5.8 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 46.8	no trial data cached
Pneumonia (lung infection)	243	3.4 3.0–3.8ROR 3.5 · χ² 411 / p 1e-91	3.4 EB05 3.0 · IC025 +1.5 3/3 methods agree	Labeled (related wording) related wording	serious PRR 2.5	no trial data cached
Hospitalisation	236	7.0 6.2–7.9ROR 7.3 · χ² 1,208 / p 7e-265	6.9 EB05 6.2 · IC025 +2.6 3/3 methods agree	Reporting / coding artifact	serious PRR 5.1	no trial data cached
Insomnia (trouble sleeping)	202	3.4 3.0–3.9ROR 3.5 · χ² 345 / p 3e-77	3.4 EB05 3.0 · IC025 +1.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 3.8 · 76% consumer	no trial data cached
Fall	195	2.6 2.3–3.0ROR 2.7 · χ² 200 / p 1e-45	2.6 EB05 2.3 · IC025 +1.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 2.1 · 77% consumer	no trial data cached
Lethargy	160	12.5 10.8–14.6ROR 12.9 · χ² 1,687 / p <1e-300	12.4 EB05 10.9 · IC025 +3.3 3/3 methods agree	Labeled — boxed warning exact term	serious PRR 11.6 · 79% consumer	no trial data cached
Aggression	155	13.9 11.9–16.3ROR 14.4 · χ² 1,846 / p <1e-300	13.8 EB05 12.1 · IC025 +3.5 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.2 · 74% consumer	no trial data cached
Product use issue	146	3.5 3.0–4.1ROR 3.6 · χ² 262 / p 3e-59	3.5 EB05 3.0 · IC025 +1.5 3/3 methods agree	Reporting / coding artifact	serious PRR 5.5 · 74% consumer	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.

Mitral valve incompetence — n=363, PRR 148.9
Hypersomnia — n=106, PRR 16.7
Pericardial effusion — n=74, PRR 14.5
Pharyngitis streptococcal — n=32, PRR 13.3
Abnormal behaviour — n=92, PRR 10.4
Prescribed overdose — n=44, PRR 10.2
Myoclonus — n=27, PRR 10.2
Psychomotor hyperactivity — n=36, PRR 9.7
Muscle twitching — n=42, PRR 8.2
Prescribed underdose — n=36, PRR 8.1

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 Fenfluramine?

In FDA FAERS, the most frequently co-reported reaction terms for Fenfluramine are seizure, decreased appetite, somnolence, weight decreased, mitral valve incompetence, generalised tonic-clonic seizure. 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 Fenfluramine have an FDA boxed warning?

Yes. The current FDA label carries a boxed warning: VALVULAR HEART DISEASE and PULMONARY ARTERIAL HYPERTENSION FINTEPLA can cause valvular heart disease and pulmonary arterial hypertension [see Warnings and Precautions (5.1) ]. Echocardiogram assessments are required before, during, and after treatment with FINTEPLA.

Do FAERS signals prove that Fenfluramine 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 e88f360e-33ad-4cd6-b2de-5ef885857c5d, effective 20251027; matched on openfda.generic_name.exact:"FENFLURAMINE")
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, 156 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.