Febuxostat 40 side effects: what 10,109 FDA adverse event reports show
Drug class
Xanthine Oxidase Inhibitor
Label matched
Febuxostat Tablets 40 Mg (Febuxostat)
Who reports
10,109 reports · 94% serious · 1,659 with death outcome · 31% female
Used for
Febuxostat is a xanthine oxidase (XO) inhibitor indicated for the chronic management of hyperuricemia in adult patients with gout who have an inadequate response to a maximally titrated dose of allopurinol, who are intolerant to allopurinol, or for whom treatment with allopurinol is not advisable. Limitations of Use: Febuxostat is not recommended for the treatment of asymptomatic hyperuricemia.
What it is
Febuxostat is a xanthine oxidase inhibitor. The active ingredient in febuxostat is 2-[3-cyano-4-(2-methylpropoxy) phenyl]-4-methylthiazole-5-carboxylic acid, with a molecular weight of 316.38.
Boxed warning
WARNING : CARDIOVASCULAR DEATH Gout patients with established cardiovascular (CV) disease treated with febuxostat had a higher rate of CV death compared to those treated with allopurinol in a CV outcomes study [ see Warnings and Precautions ( 5.1 )]. Consider the risks and benefits of febuxostat when deciding to prescribe or continue patients on febuxostat.
Causality screen of the 40 strongest signals
What the badges mean
- 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. 1,001 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 |
|---|---|---|---|---|---|---|
| Red blood cell sedimentation rate | 116 | 1,464.9 1,155.1–1,857.7ROR 1,481.9 · χ² 98,035 / p <1e-300 | 747.9 EB05 640.5 · IC025 +7.2 3/3 methods agree | Lab value / disease marker | serious n=116 · ♀ 72% (drug 31%) · 91% clinician | no trial data cached |
| Congenital diaphragmatic anomaly | 10 | 786.8 379.5–1,631.2ROR 787.6 · χ² 5,115 / p <1e-300 | 272.6 EB05 158.2 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Cytomegalovirus nephritis | 11 | 548.9 282.2–1,067.5ROR 549.5 · χ² 4,321 / p <1e-300 | 247.3 EB05 147.4 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=11 | no trial data cached |
| Splenic necrosis | 13 | 369.4 204.7–666.6ROR 369.8 · χ² 3,739 / p <1e-300 | 214.7 EB05 133.5 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Granuloma skin | 125 | 369.0 305.3–446.0ROR 373.6 · χ² 38,556 / p <1e-300 | 298.5 EB05 257.1 · IC025 +6.8 3/3 methods agree | Not in label — unassessed | serious n=125 · ♀ 74% (drug 31%) · 92% clinician | no trial data cached |
| Polycystic liver disease | 13 | 286.0 160.1–510.8ROR 286.3 · χ² 2,994 / p <1e-300 | 183.7 EB05 114.3 · IC025 +3.7 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Enthesopathy | 187 | 279.2 240.0–324.9ROR 284.5 · χ² 45,376 / p <1e-300 | 239.8 EB05 212.3 · IC025 +7.0 3/3 methods agree | Not in label — unassessed | serious n=187 · ♀ 57% (drug 31%) | no trial data cached |
| Blood parathyroid hormone decreased | 144 | 221.8 187.0–263.2ROR 225.0 · χ² 28,362 / p <1e-300 | 195.1 EB05 169.8 · IC025 +6.6 3/3 methods agree | Lab value / disease marker | serious n=144 · ♀ 76% (drug 31%) · 91% clinician | no trial data cached |
| Osteoma | 13 | 160.2 91.1–281.6ROR 160.4 · χ² 1,763 / p <1e-300 | 122.4 EB05 76.1 · IC025 +3.6 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Tenosynovitis | 188 | 151.4 130.7–175.3ROR 154.2 · χ² 26,010 / p <1e-300 | 139.0 EB05 123.1 · IC025 +6.4 3/3 methods agree | Not in label — unassessed | serious n=188 · ♀ 57% (drug 31%) | no trial data cached |
| Haemoglobin urine present | 13 | 140.7 80.2–246.8ROR 140.9 · χ² 1,559 / p <1e-300 | 110.7 EB05 68.9 · IC025 +3.6 3/3 methods agree | Lab value / disease marker | serious n=13 | no trial data cached |
| Alanine aminotransferase abnormal | 133 | 140.4 117.9–167.2ROR 142.3 · χ² 17,097 / p <1e-300 | 129.0 EB05 111.7 · IC025 +6.2 3/3 methods agree | Lab value / disease marker | serious n=133 | no trial data cached |
| Splenic cyst | 13 | 135.7 77.4–237.8ROR 135.9 · χ² 1,506 / p <1e-300 | 107.6 EB05 66.9 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Panniculitis | 144 | 131.7 111.4–155.8ROR 133.6 · χ² 17,434 / p <1e-300 | 121.9 EB05 106.1 · IC025 +6.2 3/3 methods agree | Not in label — unassessed | serious n=144 · ♀ 77% (drug 31%) · 91% clinician | no trial data cached |
| Respiratory tract haemorrhage | 33 | 121.2 85.4–172.1ROR 121.6 · χ² 3,601 / p <1e-300 | 107.5 EB05 80.1 · IC025 +4.8 3/3 methods agree | Not in label — unassessed | serious n=33 · ♀ 0% (drug 31%) · 100% clinician | no trial data cached |
| Activated partial thromboplastin time abnormal | 13 | 115.6 66.2–202.1ROR 115.8 · χ² 1,292 / p 3e-283 | 94.7 EB05 58.9 · IC025 +3.5 3/3 methods agree | Lab value / disease marker | serious n=13 | no trial data cached |
| Rheumatoid nodule | 143 | 112.3 95.0–132.7ROR 113.9 · χ² 14,844 / p <1e-300 | 105.0 EB05 91.3 · IC025 +6.0 3/3 methods agree | Not in label — unassessed | serious n=143 · ♀ 77% (drug 31%) · 91% clinician | no trial data cached |
| Metastases to soft tissue | 13 | 108.6 62.2–189.6ROR 108.7 · χ² 1,215 / p 1e-266 | 89.9 EB05 55.9 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Rheumatoid lung | 45 | 101.6 75.4–137.0ROR 102.1 · χ² 4,176 / p <1e-300 | 93.1 EB05 72.4 · IC025 +5.1 3/3 methods agree | Not in label — unassessed | serious n=45 · ♀ 74% (drug 31%) | no trial data cached |
| Splenic lesion | 14 | 82.1 48.1–140.0ROR 82.2 · χ² 1,001 / p 5e-220 | 71.5 EB05 45.3 · IC025 +3.5 3/3 methods agree | Not in label — unassessed | serious n=14 | no trial data cached |
| Lordosis | 13 | 79.4 45.6–138.1ROR 79.5 · χ² 895 / p 7e-197 | 69.0 EB05 42.9 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| C-reactive protein abnormal | 183 | 61.0 52.7–70.5ROR 62.1 · χ² 10,426 / p <1e-300 | 58.9 EB05 52.1 · IC025 +5.4 3/3 methods agree | Lab value / disease marker | serious n=183 · ♀ 57% (drug 31%) | no trial data cached |
| Skin necrosis | 148 | 60.7 51.6–71.4ROR 61.5 · χ² 8,379 / p <1e-300 | 58.5 EB05 51.0 · IC025 +5.4 3/3 methods agree | Not in label — unassessed | serious n=147 · ♀ 76% (drug 31%) · 91% clinician | no trial data cached |
| Tongue disorder | 187 | 54.6 47.3–63.1ROR 55.6 · χ² 9,537 / p <1e-300 | 52.9 EB05 46.9 · IC025 +5.3 3/3 methods agree | Not in label — unassessed | serious n=187 · ♀ 57% (drug 31%) | no trial data cached |
| Drug tolerance decreased | 70 | 53.2 42.0–67.3ROR 53.5 · χ² 3,441 / p <1e-300 | 51.2 EB05 41.9 · IC025 +4.9 3/3 methods agree | Not in label — unassessed | serious n=69 · ♀ 84% (drug 31%) | no trial data cached |
| Blood uric acid decreased | 11 | 47.9 26.3–87.0ROR 47.9 · χ² 449 / p 7e-100 | 43.5 EB05 25.9 · IC025 +2.9 3/3 methods agree | Lab value / disease marker | serious n=10 | no trial data cached |
| Pneumonia haemophilus | 10 | 43.4 23.2–81.2ROR 43.5 · χ² 365 / p 9e-82 | 39.6 EB05 23.0 · IC025 +2.8 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Urinary sediment present | 13 | 42.9 24.8–74.3ROR 42.9 · χ² 481 / p 7e-107 | 39.8 EB05 24.7 · IC025 +3.1 3/3 methods agree | Lab value / disease marker | serious n=13 | no trial data cached |
| Gouty arthritis | 16 | 42.5 25.9–69.7ROR 42.6 · χ² 595 / p 9e-132 | 39.8 EB05 26.0 · IC025 +3.4 3/3 methods agree | Not in label — unassessed | serious n=16 | no trial data cached |
| Cerebral artery thrombosis | 10 | 40.9 21.9–76.5ROR 41.0 · χ² 344 / p 5e-77 | 37.5 EB05 21.7 · IC025 +2.7 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Prothrombin time abnormal | 13 | 39.7 22.9–68.7ROR 39.7 · χ² 444 / p 8e-99 | 37.0 EB05 23.0 · IC025 +3.1 3/3 methods agree | Lab value / disease marker | serious n=13 | no trial data cached |
| Hyperuricaemia | 76 | 39.1 31.2–49.1ROR 39.4 · χ² 2,735 / p <1e-300 | 38.1 EB05 31.4 · IC025 +4.6 3/3 methods agree | Likely indication confounding shares a disease stem with the indications wording | serious n=75 | no trial data cached |
| Orthostatic intolerance | 13 | 38.5 22.2–66.6ROR 38.5 · χ² 430 / p 9e-96 | 36.0 EB05 22.4 · IC025 +3.1 3/3 methods agree | Not in label — unassessed | serious n=13 | no trial data cached |
| Thalamus haemorrhage | 16 | 38.4 23.4–63.0ROR 38.5 · χ² 536 / p 6e-119 | 36.2 EB05 23.7 · IC025 +3.3 3/3 methods agree | Not in label — unassessed | serious n=16 | no trial data cached |
| Granuloma | 60 | 36.6 28.4–47.2ROR 36.8 · χ² 2,006 / p <1e-300 | 35.6 EB05 28.7 · IC025 +4.4 3/3 methods agree | Not in label — unassessed | serious n=60 · ♀ 76% (drug 31%) | no trial data cached |
| Red blood cells urine positive | 16 | 34.8 21.2–57.0ROR 34.8 · χ² 484 / p 2e-107 | 33.0 EB05 21.5 · IC025 +3.2 3/3 methods agree | Lab value / disease marker | serious n=15 | no trial data cached |
| Systemic infection | 27 | 34.2 23.4–50.0ROR 34.3 · χ² 824 / p 2e-181 | 33.0 EB05 23.8 · IC025 +3.8 3/3 methods agree | Labeled (related wording) related wording | serious n=27 · ♀ 57% (drug 31%) · 100% clinician | no trial data cached |
| Transformation to acute myeloid leukaemia | 10 | 32.0 17.1–59.8ROR 32.0 · χ² 266 / p 4e-60 | 29.9 EB05 17.2 · IC025 +2.6 3/3 methods agree | Not in label — unassessed | serious n=10 | no trial data cached |
| Drug monitoring procedure incorrectly performed | 10 | 31.5 16.9–58.8ROR 31.6 · χ² 262 / p 4e-59 | 29.4 EB05 16.9 · IC025 +2.6 3/3 methods agree | Reporting / coding artifact | serious n=9 | no trial data cached |
| Cardiac failure chronic | 63 | 31.2 24.3–39.9ROR 31.3 · χ² 1,782 / p <1e-300 | 30.4 EB05 24.6 · IC025 +4.2 3/3 methods agree | Labeled (related wording) related wording | serious n=63 · 97% clinician | 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 |
|---|---|---|---|---|---|---|
| Acute kidney injury (sudden kidney damage) | 612 | 8.4 7.7–9.0ROR 8.8 · χ² 3,973 / p <1e-300 | 8.3 EB05 7.8 · IC025 +2.9 3/3 methods agree | Labeled (related wording) related wording | serious PRR 5.1 · 95% clinician | no trial data cached |
| Off label use (used outside approved label) | 556 | 1.3 1.2–1.4ROR 1.3 · χ² 47 / p 4e-12 | 1.3 EB05 1.2 · IC025 +0.3 | Reporting / coding artifact | serious PRR 1.5 | no trial data cached |
| Diarrhoea (diarrhea) | 538 | 1.7 1.6–1.9ROR 1.8 · χ² 172 / p 1e-39 | 1.7 EB05 1.6 · IC025 +0.7 | Labeled adverse reaction exact term | serious PRR 1.7 | no trial data cached |
| Anaemia (low red blood cells) | 501 | 5.5 5.0–5.9ROR 5.7 · χ² 1,831 / p <1e-300 | 5.4 EB05 5.0 · IC025 +2.3 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 3.6 · 91% clinician | no trial data cached |
| Nausea | 490 | 1.3 1.2–1.4ROR 1.3 · χ² 33 / p 6e-9 | 1.3 EB05 1.2 · IC025 +0.2 | Labeled adverse reaction exact term | serious PRR 1.4 | no trial data cached |
| Renal impairment | 446 | 11.1 10.1–12.2ROR 11.6 · χ² 4,087 / p <1e-300 | 11.0 EB05 10.2 · IC025 +3.3 3/3 methods agree | Labeled adverse reaction exact term | serious PRR 7.0 · 92% clinician | no trial data cached |
| Pyrexia (fever) | 434 | 2.6 2.4–2.9ROR 2.7 · χ² 433 / p 2e-96 | 2.6 EB05 2.4 · IC025 +1.2 3/3 methods agree | Not in label — unassessed | serious PRR 2.0 | no trial data cached |
| Dyspnoea (shortness of breath) | 402 | 1.5 1.3–1.6ROR 1.5 · χ² 63 / p 1e-15 | 1.5 EB05 1.4 · IC025 +0.4 | Labeled adverse reaction exact term | serious PRR 1.2 | no trial data cached |
| Rash | 399 | 1.9 1.7–2.1ROR 1.9 · χ² 175 / p 2e-40 | 1.9 EB05 1.8 · IC025 +0.8 | Labeled adverse reaction exact term | serious PRR 2.4 | no trial data cached |
| Drug ineffective (drug did not work) | 389 | 0.6 0.6–0.7ROR 0.6 · χ² 101 / p 4e-24 | 0.6 EB05 0.6 · IC025 -0.9 PRR-only: not supported by EBGM or IC | Reporting / coding artifact | serious PRR 1.0 | no trial data cached |
| Cardiac failure (heart failure) | 385 | 10.0 9.0–11.0ROR 10.3 · χ² 3,099 / p <1e-300 | 9.9 EB05 9.1 · IC025 +3.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 6.1 · 92% clinician | no trial data cached |
| Pneumonia (lung infection) | 381 | 2.4 2.2–2.7ROR 2.5 · χ² 329 / p 8e-74 | 2.4 EB05 2.2 · IC025 +1.1 3/3 methods agree | Labeled (related wording) related wording | serious PRR 1.6 · 90% clinician | no trial data cached |
| Headache | 367 | 1.2 1.1–1.3ROR 1.2 · χ² 14 / p 8e-5 | 1.2 EB05 1.1 · IC025 +0.1 | Labeled adverse reaction exact term | serious PRR 1.5 | no trial data cached |
| Decreased appetite (loss of appetite) | 354 | 3.2 2.9–3.5ROR 3.3 · χ² 530 / p 2e-117 | 3.2 EB05 2.9 · IC025 +1.5 3/3 methods agree | Labeled (related wording) related wording | serious PRR 2.9 | no trial data cached |
| Fatigue (tiredness) | 319 | 0.9 0.8–0.9ROR 0.8 · χ² 8 / p 0.002 | 0.9 EB05 0.8 · IC025 -0.4 PRR-only: not supported by EBGM or IC | Labeled adverse reaction exact term | serious PRR 0.9 | 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.
- Granuloma skin — n=125, PRR 369.0
- Enthesopathy — n=187, PRR 279.2
- Tenosynovitis — n=188, PRR 151.4
- Panniculitis — n=144, PRR 131.7
- Respiratory tract haemorrhage — n=33, PRR 121.2
- Rheumatoid nodule — n=143, PRR 112.3
- Rheumatoid lung — n=45, PRR 101.6
- Skin necrosis — n=148, PRR 60.7
- Tongue disorder — n=187, PRR 54.6
- Drug tolerance decreased — n=70, PRR 53.2
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 Febuxostat 40?
In FDA FAERS, the most frequently co-reported reaction terms for Febuxostat 40 are acute kidney injury, diarrhoea, anaemia, nausea, renal impairment, pyrexia. 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 Febuxostat 40 have an FDA boxed warning?
Yes. The current FDA label carries a boxed warning: WARNING : CARDIOVASCULAR DEATH Gout patients with established cardiovascular (CV) disease treated with febuxostat had a higher rate of CV death compared to those treated with allopurinol in a CV outcomes study [ see Warnings and Precautions ( 5.1 )]. Consider the risks and benefits of febuxostat when deciding to prescribe or continue patients on febuxostat.
Do FAERS signals prove that Febuxostat 40 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 77875ed1-049e-421b-a8d5-569b4af4a1b5, effective 20230916; matched on
openfda.generic_name.exact:"FEBUXOSTAT TABLETS 40 MG") - 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, 1,041 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.