Mefenamic Acid side effects: what 2,183 FDA adverse event reports show
Drug class
Nonsteroidal Anti-inflammatory Drug
Who reports
2,183 reports · 95% serious · 107 with death outcome · 78% female
Used for
Mefenamic acid capsules are nonsteroidal anti-inflammatory drug indicated for: For management of mild to moderate pain in patient 14 years of age and older, when therapy will not exceed one week (7 days). ( 1.1 ) For treatment of primary dysmenorrhea. .
What it is
Mefenamic acid capsules USP contains active moiety mefenamic acid, which is a member of the fenamate group of nonsteroidal anti-inflammatory drugs (NSAIDs).
Boxed warning
RISK OF SERIOUS CARDIOVASCULAR and GASTROINTESTINAL EVENTS Cardiovascular Thrombotic Events Nonsteroidal anti-inflammatory drugs (NSAIDs) cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal.
Causality screen of the 40 strongest signals
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.
- 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. 188 further terms are in the interactive explorer. Reaction links open the term's cross-drug page.
| Reaction | Reports | PRR 95% CI · ROR · χ²/p | EBGM EB05 · IC025 | Label screen | Serious-only & strata | Trial cross-check |
|---|---|---|---|---|---|---|
| Spinal pain | 44 | 36.2 27.0–48.6ROR 37.0 · χ² 1,468 / p <1e-300 | 35.6 EB05 27.6 · IC025 +4.2 3/3 methods agree | Not in label — unassessed | serious PRR 28.6 · 93% clinician | no trial data cached |
| Irritable bowel syndrome | 70 | 31.6 25.1–39.8ROR 32.6 · χ² 2,038 / p <1e-300 | 31.2 EB05 25.6 · IC025 +4.3 3/3 methods agree | Not in label — unassessed | serious PRR 23.9 · ♀ 100% (drug 78%) | no trial data cached |
| Ankylosing spondylitis | 40 | 29.6 21.8–40.2ROR 30.1 · χ² 1,074 / p 9e-236 | 29.1 EB05 22.3 · IC025 +3.9 3/3 methods agree | Not in label — unassessed | serious PRR 20.4 · ♀ 28% (drug 78%) | no trial data cached |
| Body temperature decreased | 26 | 25.2 17.2–37.0ROR 25.5 · χ² 580 / p 2e-128 | 24.8 EB05 17.7 · IC025 +3.5 3/3 methods agree | Lab value / disease marker | serious PRR 17.0 · 96% clinician | no trial data cached |
| Incontinence | 27 | 24.6 16.9–35.7ROR 24.9 · χ² 586 / p 1e-129 | 24.1 EB05 17.4 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious PRR 20.0 · ♀ 100% (drug 78%) · 96% clinician | no trial data cached |
| Retinal detachment | 22 | 23.0 15.2–34.9ROR 23.3 · χ² 441 / p 3e-98 | 22.6 EB05 15.7 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 14.1 · ♀ 100% (drug 78%) · 100% clinician | no trial data cached |
| Poor venous access | 22 | 20.5 13.5–31.1ROR 20.7 · χ² 389 / p 8e-87 | 20.1 EB05 13.9 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=22 · ♀ 100% (drug 78%) · 100% clinician | no trial data cached |
| Synovitis | 38 | 20.3 14.8–27.8ROR 20.6 · χ² 676 / p 2e-149 | 20.0 EB05 15.2 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious PRR 12.9 | no trial data cached |
| Autoimmune disorder | 20 | 20.1 13.0–31.1ROR 20.3 · χ² 344 / p 5e-77 | 19.7 EB05 13.3 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 13.0 | no trial data cached |
| Peripheral coldness | 28 | 19.6 13.5–28.3ROR 19.8 · χ² 474 / p 2e-105 | 19.3 EB05 13.9 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 18.0 · ♀ 100% (drug 78%) · 93% clinician | no trial data cached |
| Stress | 135 | 18.1 15.3–21.3ROR 19.2 · χ² 2,163 / p <1e-300 | 18.0 EB05 15.6 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious PRR 18.2 | no trial data cached |
| Mydriasis | 21 | 15.8 10.3–24.1ROR 15.9 · χ² 276 / p 3e-62 | 15.3 EB05 10.2 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 12.4 · ♀ 20% (drug 78%) | no trial data cached |
| Immunodeficiency | 24 | 15.7 10.5–23.4ROR 15.8 · χ² 315 / p 9e-71 | 15.3 EB05 10.5 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 10.3 · ♀ 100% (drug 78%) · 92% clinician | no trial data cached |
| Feeling cold | 44 | 15.2 11.3–20.3ROR 15.5 · χ² 569 / p 6e-126 | 15.0 EB05 11.5 · IC025 +3.2 3/3 methods agree | Not in label — unassessed | serious PRR 15.5 · ♀ 100% (drug 78%) | no trial data cached |
| Uveitis | 20 | 14.2 9.2–22.0ROR 14.4 · χ² 233 / p 6e-53 | 13.6 EB05 8.8 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 9.2 | no trial data cached |
| Musculoskeletal disorder | 28 | 14.1 9.7–20.3ROR 14.2 · χ² 327 / p 2e-73 | 13.7 EB05 9.6 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 13.1 | no trial data cached |
| Loss of personal independence in daily activities | 69 | 14.0 11.1–17.6ROR 14.4 · χ² 818 / p 3e-180 | 13.8 EB05 11.2 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious PRR 11.0 · ♀ 98% (drug 78%) | no trial data cached |
| Toothache | 26 | 13.8 9.4–20.3ROR 14.0 · χ² 297 / p 9e-67 | 13.4 EB05 9.3 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious PRR 15.8 · 92% clinician | no trial data cached |
| Drug intolerance | 138 | 13.8 11.7–16.2ROR 14.7 · χ² 1,630 / p <1e-300 | 13.7 EB05 11.9 · IC025 +3.4 3/3 methods agree | Reporting / coding artifact | serious PRR 13.1 · ♀ 99% (drug 78%) | no trial data cached |
| Metastases to bone | 23 | 13.5 9.0–20.3ROR 13.7 · χ² 254 / p 2e-57 | 12.9 EB05 8.7 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 8.3 · 100% clinician | no trial data cached |
| Blood potassium increased | 22 | 13.0 8.6–19.8ROR 13.2 · χ² 233 / p 8e-53 | 12.4 EB05 8.2 · IC025 +2.6 3/3 methods agree | Labeled (related wording) related wording | serious PRR 10.3 · ♀ 100% (drug 78%) · 100% clinician | no trial data cached |
| Tubulointerstitial nephritis | 25 | 12.8 8.7–19.0ROR 13.0 · χ² 261 / p 5e-59 | 12.3 EB05 8.4 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious PRR 7.8 · 91% clinician | no trial data cached |
| Oral discomfort | 18 | 12.4 7.9–19.7ROR 12.5 · χ² 178 / p 7e-41 | 11.5 EB05 7.2 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious n=18 | no trial data cached |
| Psoriatic arthropathy | 52 | 12.4 9.5–16.3ROR 12.7 · χ² 536 / p 7e-119 | 12.2 EB05 9.5 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 9.5 | no trial data cached |
| Photosensitivity reaction (sun sensitivity) | 21 | 12.3 8.0–18.8ROR 12.4 · χ² 206 / p 4e-47 | 11.5 EB05 7.5 · IC025 +2.5 3/3 methods agree | Labeled (related wording) related wording | serious PRR 11.8 · 90% clinician | no trial data cached |
| Toxic epidermal necrolysis (severe skin peeling reaction) | 19 | 12.1 7.7–19.0ROR 12.2 · χ² 183 / p 6e-42 | 11.2 EB05 7.1 · IC025 +2.5 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 7.4 | no trial data cached |
| Stevens-johnson syndrome (severe blistering skin reaction) | 28 | 12.1 8.4–17.5ROR 12.2 · χ² 274 / p 8e-62 | 11.5 EB05 8.1 · IC025 +2.7 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 7.4 · ♀ 38% (drug 78%) · 93% clinician | no trial data cached |
| Inflammatory bowel disease | 12 | 11.7 6.7–20.6ROR 11.8 · χ² 107 / p 2e-25 | 10.0 EB05 5.5 · IC025 +2.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 7.3 | no trial data cached |
| Drug reaction with eosinophilia and systemic symptoms | 31 | 11.7 8.2–16.6ROR 11.8 · χ² 292 / p 1e-65 | 11.1 EB05 8.0 · IC025 +2.7 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 7.1 | no trial data cached |
| Angioedema (deep swelling of face/throat) | 52 | 11.3 8.7–14.8ROR 11.6 · χ² 480 / p 1e-106 | 11.0 EB05 8.6 · IC025 +2.9 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 7.3 · 90% clinician | no trial data cached |
| Subarachnoid haemorrhage | 12 | 11.3 6.4–19.9ROR 11.4 · χ² 103 / p 2e-24 | 9.6 EB05 5.3 · IC025 +2.0 3/3 methods agree | Not in label — unassessed | serious PRR 6.9 | no trial data cached |
| Gastritis | 30 | 11.0 7.7–15.7ROR 11.1 · χ² 262 / p 3e-59 | 10.4 EB05 7.4 · IC025 +2.6 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 7.5 · 93% clinician | no trial data cached |
| Disturbance in attention | 61 | 10.9 8.5–13.9ROR 11.1 · χ² 536 / p 6e-119 | 10.6 EB05 8.4 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 9.5 · ♀ 98% (drug 78%) | no trial data cached |
| Contraindicated product administered | 34 | 10.8 7.8–15.1ROR 11.0 · χ² 294 / p 3e-66 | 10.3 EB05 7.5 · IC025 +2.7 3/3 methods agree | Reporting / coding artifact | serious PRR 8.2 | no trial data cached |
| Fibromyalgia | 27 | 10.7 7.3–15.6ROR 10.8 · χ² 228 / p 1e-51 | 10.0 EB05 6.9 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 7.9 | no trial data cached |
| Discomfort | 66 | 10.5 8.3–13.3ROR 10.8 · χ² 557 / p 2e-123 | 10.2 EB05 8.2 · IC025 +2.9 3/3 methods agree | Not in label — unassessed | serious PRR 11.2 | no trial data cached |
| Musculoskeletal stiffness | 95 | 10.4 8.6–12.7ROR 10.9 · χ² 802 / p 8e-177 | 10.2 EB05 8.6 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 10.3 | no trial data cached |
| C-reactive protein increased | 39 | 10.3 7.6–14.1ROR 10.5 · χ² 319 / p 1e-71 | 9.8 EB05 7.3 · IC025 +2.7 3/3 methods agree | Lab value / disease marker | serious PRR 6.5 · ♀ 56% (drug 78%) | no trial data cached |
| Rheumatoid arthritis | 121 | 10.3 8.7–12.2ROR 10.8 · χ² 1,010 / p 5e-222 | 10.1 EB05 8.7 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 7.6 | no trial data cached |
| Therapeutic response decreased | 64 | 10.2 8.0–13.0ROR 10.5 · χ² 523 / p 4e-116 | 9.9 EB05 7.9 · IC025 +2.8 3/3 methods agree | Reporting / coding artifact | serious PRR 15.3 · ♀ 100% (drug 78%) | no trial data cached |
Trial evidence (ClinicalTrials.gov)
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 |
|---|---|---|---|---|---|---|
| Arthralgia (joint pain) | 155 | 3.6 3.1–4.2ROR 3.8 · χ² 294 / p 4e-66 | 3.6 EB05 3.1 · IC025 +1.6 3/3 methods agree | Not in label — unassessed | serious PRR 3.9 | no trial data cached |
| Pain in extremity | 142 | 4.6 3.9–5.4ROR 4.9 · χ² 405 / p 2e-90 | 4.6 EB05 4.0 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 4.9 | no trial data cached |
| Drug intolerance | 138 | 13.8 11.7–16.2ROR 14.7 · χ² 1,630 / p <1e-300 | 13.7 EB05 11.9 · IC025 +3.4 3/3 methods agree | Reporting / coding artifact | serious PRR 13.1 · ♀ 99% (drug 78%) | no trial data cached |
| Stress | 135 | 18.1 15.3–21.3ROR 19.2 · χ² 2,163 / p <1e-300 | 18.0 EB05 15.6 · IC025 +3.8 3/3 methods agree | Not in label — unassessed | serious PRR 18.2 | no trial data cached |
| Rheumatoid arthritis | 121 | 10.3 8.7–12.2ROR 10.8 · χ² 1,010 / p 5e-222 | 10.1 EB05 8.7 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 7.6 | no trial data cached |
| Peripheral swelling | 112 | 7.0 5.9–8.4ROR 7.3 · χ² 576 / p 2e-127 | 6.8 EB05 5.8 · IC025 +2.5 3/3 methods agree | Not in label — unassessed | serious PRR 7.3 | no trial data cached |
| Abdominal pain upper | 98 | 4.6 3.8–5.6ROR 4.8 · χ² 274 / p 8e-62 | 4.5 EB05 3.8 · IC025 +1.8 3/3 methods agree | Labeled (related wording) related wording | serious PRR 5.1 | no trial data cached |
| Urticaria (hives) | 95 | 5.5 4.5–6.7ROR 5.7 · χ² 347 / p 1e-77 | 5.3 EB05 4.5 · IC025 +2.1 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 6.6 | no trial data cached |
| Musculoskeletal stiffness | 95 | 10.4 8.6–12.7ROR 10.9 · χ² 802 / p 8e-177 | 10.2 EB05 8.6 · IC025 +3.0 3/3 methods agree | Not in label — unassessed | serious PRR 10.3 | no trial data cached |
| Drug hypersensitivity | 94 | 4.7 3.8–5.7ROR 4.8 · χ² 268 / p 1e-60 | 4.6 EB05 3.8 · IC025 +1.8 3/3 methods agree | Labeled (related wording) related wording | serious PRR 7.1 | no trial data cached |
| Joint swelling | 88 | 7.0 5.7–8.6ROR 7.3 · χ² 451 / p 2e-100 | 6.8 EB05 5.7 · IC025 +2.4 3/3 methods agree | Not in label — unassessed | serious PRR 7.3 | no trial data cached |
| Myalgia (muscle pain) | 85 | 4.8 3.9–5.9ROR 5.0 · χ² 254 / p 1e-57 | 4.7 EB05 3.9 · IC025 +1.9 3/3 methods agree | Not in label — unassessed | serious PRR 5.0 | no trial data cached |
| Tremor (shaking) | 83 | 4.8 3.9–5.9ROR 5.0 · χ² 248 / p 4e-56 | 4.7 EB05 3.9 · IC025 +1.9 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 4.6 | no trial data cached |
| Migraine | 81 | 8.2 6.6–10.2ROR 8.5 · χ² 508 / p 1e-112 | 7.9 EB05 6.6 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious PRR 9.3 · ♀ 100% (drug 78%) | no trial data cached |
| Paraesthesia (tingling/numbness) | 78 | 4.8 3.8–5.9ROR 4.9 · χ² 229 / p 5e-52 | 4.6 EB05 3.8 · IC025 +1.8 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 5.1 · ♀ 100% (drug 78%) | 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.
- Spinal pain — n=44, PRR 36.2
- Irritable bowel syndrome — n=70, PRR 31.6
- Ankylosing spondylitis — n=40, PRR 29.6
- Incontinence — n=27, PRR 24.6
- Retinal detachment — n=22, PRR 23.0
- Poor venous access — n=22, PRR 20.5
- Synovitis — n=38, PRR 20.3
- Autoimmune disorder — n=20, PRR 20.1
- Peripheral coldness — n=28, PRR 19.6
- Stress — n=135, PRR 18.1
✓ A hand-written Bradford Hill causality assessment exists for this drug: Zoledronic acid (bisphosphonates) ↔ Osteonecrosis of the jaw.
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 Mefenamic Acid?
In FDA FAERS, the most frequently co-reported reaction terms for Mefenamic Acid are arthralgia, pain in extremity, stress, rheumatoid arthritis, peripheral swelling, abdominal pain upper. 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 Mefenamic Acid have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: RISK OF SERIOUS CARDIOVASCULAR and GASTROINTESTINAL EVENTS Cardiovascular Thrombotic Events Nonsteroidal anti-inflammatory drugs (NSAIDs) cause an increased risk of serious cardiovascular thrombotic events, including myocardial infarction and stroke, which can be fatal.
Do FAERS signals prove that Mefenamic Acid 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 d15733a9-d5fd-4d5f-86ce-e7ed8c706c7f, effective 20260420; matched on
openfda.generic_name.exact:"MEFENAMIC ACID") - 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, 228 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.