Drug · FAERS side-effect profile with label screen
Baclofen side effects: what 85,584 FDA adverse event reports show
Drug class
gamma-Aminobutyric Acid-ergic Agonist
FDA label (Established Pharmacologic Class)
Who reports
85,584 reports · 67% serious · 6,458 with death outcome · 66% female
openFDA FAERS counts, all years, deduplication not applied
Used for
Baclofen tablets are useful for the alleviation of signs and symptoms of spasticity resulting from multiple sclerosis, particularly for the relief of flexor spasms and concomitant pain, clonus, and muscular rigidity. Patients should have reversible spasticity so that baclofen treatment will aid in restoring residual function.
FDA label, Indications and Usage
What it is
DESCRIPTION Baclofen, USP is a muscle relaxant and antispastic.
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 40 strongest signals
Likely indication confounding 9Reporting / coding artifact 4Lab value / disease marker 6Not in label — unassessed 21
What the badges mean
- 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. 1,167 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 |
|---|---|---|---|---|---|---|
| Gait spastic | 131 | 148.8 119.7–185.0ROR 149.0 · χ² 11,793 / p <1e-300 | 91.1 EB05 78.8 · IC025 +5.8 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=118 · ♀ 0% (drug 66%) | not reported in cached trials |
| Implant site extravasation | 224 | 96.8 82.9–113.0ROR 97.1 · χ² 15,081 / p <1e-300 | 68.9 EB05 61.7 · IC025 +5.7 3/3 methods agree | Not in label — unassessed | serious n=196 | not reported in cached trials |
| Implant site erosion | 83 | 95.2 73.8–122.7ROR 95.2 · χ² 5,475 / p <1e-300 | 67.5 EB05 56.1 · IC025 +5.2 3/3 methods agree | Not in label — unassessed | serious n=81 · ♀ 0% (drug 66%) | not reported in cached trials |
| Needle fatigue | 101 | 69.3 55.5–86.4ROR 69.4 · χ² 5,225 / p <1e-300 | 53.5 EB05 45.3 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious n=94 · ♀ 0% (drug 66%) | not reported in cached trials |
| Muscle spasticity | 2,334 | 56.7 54.3–59.3ROR 58.3 · χ² 103,420 / p <1e-300 | 46.1 EB05 44.5 · IC025 +5.4 3/3 methods agree | Likely indication confounding term in indications | serious PRR 43.6 | not reported in cached trials |
| Device damage | 141 | 51.7 43.1–62.0ROR 51.8 · χ² 5,726 / p <1e-300 | 42.5 EB05 36.9 · IC025 +4.9 3/3 methods agree | Reporting / coding artifact | serious n=136 | not reported in cached trials |
| Epidural lipomatosis | 56 | 46.8 35.2–62.3ROR 46.8 · χ² 2,064 / p <1e-300 | 38.9 EB05 31.1 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=56 · ♀ 0% (drug 66%) · 100% clinician | not reported in cached trials |
| Relapsing-remitting multiple sclerosis | 137 | 46.1 38.4–55.4ROR 46.2 · χ² 5,038 / p <1e-300 | 38.7 EB05 33.5 · IC025 +4.8 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=129 · ♀ 28% (drug 66%) | not reported in cached trials |
| Implant site infection | 346 | 44.2 39.4–49.5ROR 44.4 · χ² 12,305 / p <1e-300 | 37.4 EB05 34.2 · IC025 +5.0 3/3 methods agree | Not in label — unassessed | serious n=341 · ♀ 37% (drug 66%) | not reported in cached trials |
| Medical device site infection | 88 | 41.0 32.7–51.4ROR 41.0 · χ² 2,899 / p <1e-300 | 34.9 EB05 29.2 · IC025 +4.5 3/3 methods agree | Not in label — unassessed | serious n=87 | not reported in cached trials |
| Cerebrospinal fluid leakage | 204 | 30.4 26.3–35.1ROR 30.4 · χ² 5,120 / p <1e-300 | 27.0 EB05 24.1 · IC025 +4.4 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=199 | not reported in cached trials |
| Progressive multiple sclerosis | 112 | 25.8 21.3–31.4ROR 25.9 · χ² 2,392 / p <1e-300 | 23.3 EB05 19.9 · IC025 +4.1 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=88 | not reported in cached trials |
| Implant site swelling | 88 | 24.7 19.8–30.7ROR 24.7 · χ² 1,793 / p <1e-300 | 22.4 EB05 18.7 · IC025 +4.0 3/3 methods agree | Not in label — unassessed | serious n=79 | not reported in cached trials |
| Device battery issue | 59 | 23.8 18.2–31.0ROR 23.8 · χ² 1,150 / p 3e-252 | 21.6 EB05 17.3 · IC025 +3.8 3/3 methods agree | Reporting / coding artifact | serious n=51 · ♀ 0% (drug 66%) | not reported in cached trials |
| Secondary progressive multiple sclerosis | 163 | 23.0 19.6–27.0ROR 23.0 · χ² 3,108 / p <1e-300 | 21.0 EB05 18.4 · IC025 +4.1 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=128 | not reported in cached trials |
| Neurogenic bladder | 168 | 21.0 18.0–24.6ROR 21.1 · χ² 2,930 / p <1e-300 | 19.4 EB05 17.0 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious n=146 | not reported in cached trials |
| Soft tissue injury | 59 | 20.6 15.8–26.9ROR 20.6 · χ² 996 / p 6e-219 | 19.0 EB05 15.2 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=56 · ♀ 100% (drug 66%) · 100% clinician | not reported in cached trials |
| Urine leukocyte esterase positive | 54 | 20.2 15.3–26.6ROR 20.2 · χ² 890 / p 9e-196 | 18.6 EB05 14.7 · IC025 +3.6 3/3 methods agree | Lab value / disease marker | ♀ 100% (drug 66%) · 100% clinician | not reported in cached trials |
| Device infusion issue | 181 | 19.5 16.7–22.7ROR 19.5 · χ² 2,919 / p <1e-300 | 18.1 EB05 16.0 · IC025 +3.9 3/3 methods agree | Reporting / coding artifact | serious n=128 | not reported in cached trials |
| Jc polyomavirus test positive | 83 | 18.5 14.8–23.1ROR 18.5 · χ² 1,261 / p 2e-276 | 17.2 EB05 14.3 · IC025 +3.6 3/3 methods agree | Lab value / disease marker | serious n=56 | not reported in cached trials |
| Device alarm issue | 125 | 18.2 15.2–21.8ROR 18.2 · χ² 1,871 / p <1e-300 | 16.9 EB05 14.6 · IC025 +3.7 3/3 methods agree | Reporting / coding artifact | serious n=94 · ♀ 46% (drug 66%) | not reported in cached trials |
| Band sensation | 81 | 16.5 13.2–20.7ROR 16.5 · χ² 1,091 / p 1e-239 | 15.4 EB05 12.8 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=43 · ♀ 100% (drug 66%) · 100% consumer | not reported in cached trials |
| Jc virus test positive | 54 | 16.5 12.5–21.7ROR 16.5 · χ² 721 / p 4e-159 | 15.4 EB05 12.2 · IC025 +3.3 3/3 methods agree | Lab value / disease marker | ♀ 100% (drug 66%) · 100% consumer | not reported in cached trials |
| Monoparesis | 112 | 16.0 13.2–19.4ROR 16.0 · χ² 1,463 / p <1e-300 | 15.0 EB05 12.8 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=108 · ♀ 0% (drug 66%) | not reported in cached trials |
| Infusion site mass | 64 | 15.6 12.1–20.0ROR 15.6 · χ² 806 / p 2e-177 | 14.6 EB05 11.7 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=58 | not reported in cached trials |
| Clonus | 156 | 14.7 12.5–17.3ROR 14.7 · χ² 1,868 / p <1e-300 | 13.9 EB05 12.1 · IC025 +3.5 3/3 methods agree | Likely indication confounding term in indications | serious n=141 · ♀ 44% (drug 66%) | not reported in cached trials |
| Hypertonic bladder | 158 | 14.2 12.1–16.6ROR 14.2 · χ² 1,815 / p <1e-300 | 13.4 EB05 11.7 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=142 · ♀ 42% (drug 66%) | not reported in cached trials |
| Peroneal nerve palsy | 306 | 13.9 12.4–15.6ROR 13.9 · χ² 3,449 / p <1e-300 | 13.2 EB05 12.0 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=195 | not reported in cached trials |
| B-lymphocyte count decreased | 70 | 13.4 10.5–17.0ROR 13.4 · χ² 748 / p 7e-165 | 12.6 EB05 10.2 · IC025 +3.2 3/3 methods agree | Lab value / disease marker | – | not reported in cached trials |
| Post lumbar puncture syndrome | 54 | 13.4 10.2–17.6ROR 13.4 · χ² 573 / p 5e-127 | 12.5 EB05 9.8 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=48 · ♀ 0% (drug 66%) | not reported in cached trials |
| Trigeminal neuralgia | 207 | 13.2 11.5–15.2ROR 13.3 · χ² 2,208 / p <1e-300 | 12.5 EB05 11.2 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=173 | not reported in cached trials |
| Multiple sclerosis relapse | 3,416 | 12.7 12.3–13.1ROR 13.2 · χ² 35,051 / p <1e-300 | 12.1 EB05 11.8 · IC025 +3.5 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 11.9 | NCT03319732: 7/323 (2.2%) on Baclofen (serious AE) |
| Multiple sclerosis | 2,336 | 12.5 12.0–13.0ROR 12.8 · χ² 23,474 / p <1e-300 | 11.9 EB05 11.5 · IC025 +3.5 3/3 methods agree | Likely indication confounding term in indications | serious PRR 11.8 | NCT03319732: 7/323 (2.2%) on Baclofen (serious AE) |
| Hypertonia | 279 | 12.4 11.0–14.0ROR 12.5 · χ² 2,781 / p <1e-300 | 11.8 EB05 10.7 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=229 · ♀ 44% (drug 66%) | not reported in cached trials |
| Lymphocyte percentage decreased | 61 | 11.6 9.0–15.0ROR 11.6 · χ² 552 / p 2e-122 | 10.8 EB05 8.6 · IC025 +2.9 3/3 methods agree | Lab value / disease marker | serious n=55 · 100% clinician | not reported in cached trials |
| Areflexia | 120 | 11.4 9.5–13.7ROR 11.4 · χ² 1,078 / p 1e-236 | 10.8 EB05 9.2 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=115 · 100% clinician | not reported in cached trials |
| Neutrophil percentage increased | 56 | 11.3 8.6–14.7ROR 11.3 · χ² 491 / p 3e-109 | 10.5 EB05 8.3 · IC025 +2.9 3/3 methods agree | Lab value / disease marker | serious n=52 · 100% clinician | not reported in cached trials |
| Decubitus ulcer | 357 | 11.2 10.1–12.4ROR 11.2 · χ² 3,155 / p <1e-300 | 10.7 EB05 9.8 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 9.2 | NCT03319732: 1/323 (0.3%) on Baclofen (serious AE) |
| Encephalopathy | 1,072 | 11.2 10.5–11.9ROR 11.3 · χ² 9,489 / p <1e-300 | 10.7 EB05 10.2 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious PRR 9.3 · 96% clinician | not reported in cached trials |
| Toxic encephalopathy | 215 | 11.1 9.7–12.7ROR 11.1 · χ² 1,882 / p <1e-300 | 10.6 EB05 9.4 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious n=214 · 100% clinician | not reported in cached trials |
Trial evidence (ClinicalTrials.gov)
✓ Trial adverse-event data found on ClinicalTrials.gov
Largest completed trials with posted results that list Baclofen as a study intervention. The right-hand column of the signal table shows whether each FAERS term was also recorded in these trials, with a real denominator (3 of 40 signal terms matched).
- NCT03319732 — A Study to Evaluate the Long-term Safety of Arbaclofen Extended-Release Tablets for Patients With Spasticity D (N=323, PHASE3; 27 AE terms posted; arms: AERT 80 mg)
Caveats: trial populations, doses and follow-up differ from the reporting population; AE terms are sponsor-coded and matched here by wording; absence from a trial list means the term was not reported above the sponsor's frequency threshold, not that it cannot occur.
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 |
|---|---|---|---|---|---|---|
| Fatigue (tiredness) | 6,274 | 2.0 1.9–2.0ROR 2.1 · χ² 3,165 / p <1e-300 | 2.0 EB05 1.9 · IC025 +0.9 | Labeled adverse reaction exact term | serious PRR 1.9 | not reported in cached trials |
| Pain | 5,748 | 2.3 2.2–2.4ROR 2.4 · χ² 4,313 / p <1e-300 | 2.3 EB05 2.2 · IC025 +1.2 3/3 methods agree | Likely indication confounding term in indications; also in warnings | serious PRR 2.2 | not reported in cached trials |
| Drug ineffective (drug did not work) | 5,603 | 1.0 1.0–1.1ROR 1.0 · χ² 10 / p 6e-4 | 1.0 EB05 1.0 · IC025 +0.0 | Reporting / coding artifact | serious PRR 1.3 | not reported in cached trials |
| Fall | 5,499 | 4.1 4.0–4.2ROR 4.3 · χ² 12,895 / p <1e-300 | 4.1 EB05 4.0 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 3.1 | not reported in cached trials |
| Nausea | 4,710 | 1.5 1.4–1.5ROR 1.5 · χ² 718 / p 1e-158 | 1.5 EB05 1.4 · IC025 +0.5 | Labeled adverse reaction exact term | serious PRR 1.5 | NCT03319732: 1/323 (0.3%) on Baclofen (serious AE) |
| Headache | 4,457 | 1.7 1.7–1.8ROR 1.8 · χ² 1,463 / p <1e-300 | 1.7 EB05 1.7 · IC025 +0.8 | Labeled adverse reaction exact term | serious PRR 1.9 | NCT03319732: 24/323 (7.4%) on Baclofen |
| Gait disturbance | 4,150 | 5.4 5.2–5.6ROR 5.6 · χ² 14,655 / p <1e-300 | 5.3 EB05 5.2 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 4.2 | NCT03319732: 20/323 (6.2%) on Baclofen |
| Off label use (used outside approved label) | 3,827 | 1.1 1.0–1.1ROR 1.1 · χ² 24 / p 5e-7 | 1.1 EB05 1.1 · IC025 +0.1 | Reporting / coding artifact | serious PRR 1.3 | not reported in cached trials |
| Dizziness | 3,625 | 1.8 1.7–1.8ROR 1.8 · χ² 1,283 / p 2e-281 | 1.8 EB05 1.7 · IC025 +0.8 | Labeled adverse reaction exact term | serious PRR 1.7 | NCT03319732: 52/323 (16.1%) on Baclofen |
| Urinary tract infection (bladder infection) | 3,537 | 5.2 5.0–5.4ROR 5.4 · χ² 11,781 / p <1e-300 | 5.1 EB05 5.0 · IC025 +2.3 3/3 methods agree | Not in label — unassessed | serious PRR 4.7 | not reported in cached trials |
| Asthenia (weakness) | 3,456 | 2.3 2.2–2.3ROR 2.3 · χ² 2,457 / p <1e-300 | 2.3 EB05 2.2 · IC025 +1.1 3/3 methods agree | Not in label — unassessed | serious PRR 2.0 | NCT03319732: 61/323 (18.9%) on Baclofen |
| Multiple sclerosis relapse | 3,416 | 12.7 12.3–13.1ROR 13.2 · χ² 35,051 / p <1e-300 | 12.1 EB05 11.8 · IC025 +3.5 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious PRR 11.9 | NCT03319732: 7/323 (2.2%) on Baclofen (serious AE) |
| Muscle spasms | 3,365 | 4.6 4.4–4.7ROR 4.7 · χ² 9,247 / p <1e-300 | 4.5 EB05 4.4 · IC025 +2.1 3/3 methods agree | Likely indication confounding term in indications | serious PRR 5.1 | not reported in cached trials |
| Diarrhoea (diarrhea) | 3,145 | 1.2 1.2–1.2ROR 1.2 · χ² 106 / p 3e-25 | 1.2 EB05 1.2 · IC025 +0.2 | Labeled adverse reaction exact term | serious PRR 1.1 | not reported in cached trials |
| Vomiting | 2,898 | 1.5 1.5–1.6ROR 1.5 · χ² 519 / p 3e-115 | 1.5 EB05 1.5 · IC025 +0.5 | Labeled adverse reaction exact term | serious PRR 1.5 | NCT03319732: 29/323 (9.0%) on Baclofen |
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.
- Implant site extravasation — n=224, PRR 96.8
- Implant site erosion — n=83, PRR 95.2
- Needle fatigue — n=101, PRR 69.3
- Epidural lipomatosis — n=56, PRR 46.8
- Implant site infection — n=346, PRR 44.2
- Medical device site infection — n=88, PRR 41.0
- Implant site swelling — n=88, PRR 24.7
- Neurogenic bladder — n=168, PRR 21.0
- Soft tissue injury — n=59, PRR 20.6
- Band sensation — n=81, PRR 16.5
✓ A hand-written Bradford Hill causality assessment exists for this drug: Baclofen ↔ Somnolence.
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 Baclofen?
In FDA FAERS, the most frequently co-reported reaction terms for Baclofen are fatigue, pain, fall, nausea, headache, gait disturbance. 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 Baclofen have an FDA boxed warning?
No. The FDA label retrieved for Baclofen has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Baclofen 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 06bcfb08-2ada-f803-e063-6394a90a826b, effective 20251226; matched on
openfda.generic_name.exact:"BACLOFEN" AND openfda.product_type:"HUMAN PRESCRIPTION DRUG") - 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, 1,207 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 - ClinicalTrials.gov API v2 (query
BACLOFEN, results-bearing studies sorted by enrollment)
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.