Dantrolene side effects: what 609 FDA adverse event reports show

Dantrolene · 19 reaction terms · 299 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Who reports

609 reports · 82% serious · 73 with death outcome · 53% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Dantrolene Sodium for Injection is indicated, along with appropriate supportive measures, for the management of the fulminant hypermetabolism of skeletal muscle characteristic of malignant hyperthermia crises in patients of all ages. Dantrolene Sodium .

FDA label, Indications and Usage

What it is

DESCRIPTION Dantrolene Sodium for Injection, USP is a sterile, non-pyrogenic, lyophilized formulation. Dantrolene Sodium for Injection, USP is supplied in 100 mL vials containing 20 mg dantrol.

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 2Labeled (related wording) 1Likely indication confounding 2Reporting / coding artifact 2Not in label — unassessed 9

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.
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
Neuroleptic malignant syndrome	93	271.4 224.9–327.5ROR 320.1 · χ² 24,602 / p <1e-300	255.2 EB05 214.5 · IC025 +6.4 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 188.9 · 98% clinician	no trial data cached
Muscle rigidity	25	72.2 49.1–106.0ROR 75.2 · χ² 1,682 / p <1e-300	68.4 EB05 48.7 · IC025 +4.2 3/3 methods agree	Likely indication confounding term in indications	serious PRR 56.5 · ♀ 25% (drug 53%) · 96% clinician	no trial data cached
Inappropriate antidiuretic hormone secretion	12	40.6 23.2–71.2ROR 41.4 · χ² 425 / p 1e-94	38.3 EB05 23.4 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 28.6	no trial data cached
Muscle spasticity	13	36.1 21.1–61.9ROR 36.9 · χ² 409 / p 3e-91	34.4 EB05 21.4 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 33.3	no trial data cached
Dystonia	15	26.6 16.1–43.8ROR 27.2 · χ² 344 / p 5e-77	25.7 EB05 16.5 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 19.1	no trial data cached
Tachypnoea	10	25.4 13.8–47.0ROR 25.8 · χ² 211 / p 4e-48	24.2 EB05 13.7 · IC025 +2.5 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 18.3	no trial data cached
Rhabdomyolysis (muscle breakdown)	29	24.0 16.8–34.2ROR 25.2 · χ² 617 / p 1e-136	23.7 EB05 17.3 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 16.9 · 100% clinician	no trial data cached
Serotonin syndrome	13	23.4 13.7–40.1ROR 23.9 · χ² 257 / p 4e-58	22.6 EB05 13.8 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 16.5	no trial data cached
Incontinence	6	19.5 8.8–43.3ROR 19.7 · χ² 88 / p 4e-21	16.3 EB05 6.0 · IC025 +1.6 3/3 methods agree	Not in label — unassessed	serious PRR 18.3	no trial data cached
Drug ineffective for unapproved indication	26	16.1 11.0–23.4ROR 16.7 · χ² 353 / p 4e-79	15.7 EB05 11.1 · IC025 +3.0 3/3 methods agree	Reporting / coding artifact	serious PRR 21.3 · 96% clinician	no trial data cached
Respiratory depression	5	14.0 5.9–33.6ROR 14.2 · χ² 48 / p 2e-12	9.6 EB05 3.5 · IC025 +1.1 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 10.1	no trial data cached
Mydriasis	5	13.4 5.6–32.2ROR 13.5 · χ² 46 / p 7e-12	9.1 EB05 3.3 · IC025 +1.1 3/3 methods agree	Not in label — unassessed	serious PRR 12.1	no trial data cached
Drug toxicity	5	12.5 5.2–29.8ROR 12.6 · χ² 42 / p 5e-11	8.2 EB05 3.1 · IC025 +1.0 3/3 methods agree	Labeled (related wording) related wording	serious PRR 9.1	no trial data cached
Sedation	8	10.6 5.3–21.0ROR 10.7 · χ² 60 / p 4e-15	8.0 EB05 3.9 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 10.2	no trial data cached
Multiple sclerosis relapse	13	6.5 3.8–11.1ROR 6.6 · χ² 55 / p 6e-14	5.4 EB05 3.3 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 5.3	no trial data cached
Drug abuse	10	4.1 2.2–7.6ROR 4.2 · χ² 21 / p 3e-6	3.5 EB05 2.1 · IC025 +0.8 3/3 methods agree	Reporting / coding artifact	serious PRR 2.9	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
Neuroleptic malignant syndrome	93	271.4 224.9–327.5ROR 320.1 · χ² 24,602 / p <1e-300	255.2 EB05 214.5 · IC025 +6.4 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 188.9 · 98% clinician	no trial data cached
Rhabdomyolysis (muscle breakdown)	29	24.0 16.8–34.2ROR 25.2 · χ² 617 / p 1e-136	23.7 EB05 17.3 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 16.9 · 100% clinician	no trial data cached
Drug ineffective for unapproved indication	26	16.1 11.0–23.4ROR 16.7 · χ² 353 / p 4e-79	15.7 EB05 11.1 · IC025 +3.0 3/3 methods agree	Reporting / coding artifact	serious PRR 21.3 · 96% clinician	no trial data cached
Muscle rigidity	25	72.2 49.1–106.0ROR 75.2 · χ² 1,682 / p <1e-300	68.4 EB05 48.7 · IC025 +4.2 3/3 methods agree	Likely indication confounding term in indications	serious PRR 56.5 · ♀ 25% (drug 53%) · 96% clinician	no trial data cached
Dystonia	15	26.6 16.1–43.8ROR 27.2 · χ² 344 / p 5e-77	25.7 EB05 16.5 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 19.1	no trial data cached
Multiple sclerosis relapse	13	6.5 3.8–11.1ROR 6.6 · χ² 55 / p 6e-14	5.4 EB05 3.3 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 5.3	no trial data cached
Serotonin syndrome	13	23.4 13.7–40.1ROR 23.9 · χ² 257 / p 4e-58	22.6 EB05 13.8 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 16.5	no trial data cached
Muscle spasticity	13	36.1 21.1–61.9ROR 36.9 · χ² 409 / p 3e-91	34.4 EB05 21.4 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 33.3	no trial data cached
Inappropriate antidiuretic hormone secretion	12	40.6 23.2–71.2ROR 41.4 · χ² 425 / p 1e-94	38.3 EB05 23.4 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 28.6	no trial data cached
Drug abuse	10	4.1 2.2–7.6ROR 4.2 · χ² 21 / p 3e-6	3.5 EB05 2.1 · IC025 +0.8 3/3 methods agree	Reporting / coding artifact	serious PRR 2.9	no trial data cached
Tachypnoea	10	25.4 13.8–47.0ROR 25.8 · χ² 211 / p 4e-48	24.2 EB05 13.7 · IC025 +2.5 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 18.3	no trial data cached
Sedation	8	10.6 5.3–21.0ROR 10.7 · χ² 60 / p 4e-15	8.0 EB05 3.9 · IC025 +1.5 3/3 methods agree	Not in label — unassessed	serious PRR 10.2	no trial data cached
Incontinence	6	19.5 8.8–43.3ROR 19.7 · χ² 88 / p 4e-21	16.3 EB05 6.0 · IC025 +1.6 3/3 methods agree	Not in label — unassessed	serious PRR 18.3	no trial data cached
Drug toxicity	5	12.5 5.2–29.8ROR 12.6 · χ² 42 / p 5e-11	8.2 EB05 3.1 · IC025 +1.0 3/3 methods agree	Labeled (related wording) related wording	serious PRR 9.1	no trial data cached
Mydriasis	5	13.4 5.6–32.2ROR 13.5 · χ² 46 / p 7e-12	9.1 EB05 3.3 · IC025 +1.1 3/3 methods agree	Not in label — unassessed	serious PRR 12.1	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.

Rhabdomyolysis — n=29, PRR 24.0

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 Dantrolene?

In FDA FAERS, the most frequently co-reported reaction terms for Dantrolene are neuroleptic malignant syndrome, rhabdomyolysis, muscle rigidity, dystonia, multiple sclerosis relapse, serotonin syndrome. 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 Dantrolene have an FDA boxed warning?

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

Do FAERS signals prove that Dantrolene 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 ab0efc75-0598-4f4e-91ad-6195bb2661fe, effective 20241211; matched on openfda.generic_name.exact:"DANTROLENE")
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, 19 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.