Drug · FAERS side-effect profile with label screen
Allopurinol side effects: what 155,426 FDA adverse event reports show
Who reports
155,426 reports · 82% serious · 21,873 with death outcome · 35% female
openFDA FAERS counts, all years, deduplication not applied
Used for
1. INDICATIONS AND USAGE Allopurinol tablets are indicated for: • The management of adults with signs and symptoms of primary or secondary gout (acute attacks, tophi, joint destruction, uric acid lithiasis, and/or nephropathy) • The management of adult.
FDA label, Indications and Usage
What it is
Allopurinol is a bicyclic structure comprising a pyrazole ring fused to a hydroxy-substituted pyrimidine ring. It has a role as an antimetabolite, an EC 1.17.3.2 (xanthine oxidase) inhibitor, a gout suppressant and a radical scavenger.
PubChem CID 135401907 (ChEBI)
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
Labeled adverse reaction 4Labeled (related wording) 4Likely indication confounding 5Reporting / coding artifact 6Lab value / disease marker 3Not in label — unassessed 18
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.
- 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, for the 300 most-reported drugs, adjusted for age band), and flags pairs whose reports are unusually skewed by sex or come mostly from consumers. Each row also shows the PRR against the other drugs of the same FDA class, which removes most confounding by the condition being treated, and a calibrated p-value: on validation, known non-causes average an ROR of about 2, so significance is judged against that empirical null (✓ = p < 0.05 after calibration). 1,158 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 |
|---|---|---|---|---|---|---|
| Appendicolith | 301 | 537.3 416.7–692.9ROR 538.4 · calibrated p 6e-14 ✓ | 106.1 EB05 96.4 · IC025 +6.3 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Not in label — unassessed | serious n=301 · ♀ 0% (drug 35%) · 100% clinician | not reported in cached trials |
| Sleep disorder therapy | 118 | 236.2 174.7–319.2ROR 236.4 · calibrated p 2e-10 ✓ | 84.2 EB05 72.2 · IC025 +5.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Reporting / coding artifact | serious n=118 · ♀ 0% (drug 35%) · 100% clinician | NCT01101035: 1/3,098 (0.0%) on Allopurinol (serious AE) |
| Analgesic therapy | 133 | 103.3 82.4–129.7ROR 103.4 · calibrated p 1e-7 ✓ | 58.0 EB05 50.2 · IC025 +5.3 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Reporting / coding artifact | serious n=133 · ♀ 0% (drug 35%) · 100% clinician | not reported in cached trials |
| Drug therapy | 127 | 88.8 70.9–111.1ROR 88.8 · calibrated p 4e-7 ✓ | 53.1 EB05 45.8 · IC025 +5.2 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Reporting / coding artifact | serious n=127 · ♀ 0% (drug 35%) · 100% clinician | NCT01101035: 1/3,092 (0.0%) on Allopurinol (serious AE) |
| Multiple drug therapy | 118 | 27.3 22.4–33.3ROR 27.3 · calibrated p 5e-4 ✓ | 22.7 EB05 19.5 · IC025 +4.1 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Reporting / coding artifact | serious n=118 · ♀ 100% (drug 35%) · 100% clinician | not reported in cached trials |
| Tumour flare | 114 | 26.9 22.0–32.9ROR 26.9 · calibrated p 5e-4 ✓ | 22.4 EB05 19.2 · IC025 +4.1 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Labeled (related wording) related wording | serious n=114 · ♀ 0% (drug 35%) · 100% clinician | not reported in cached trials |
| Product monitoring error | 217 | 23.9 20.7–27.6ROR 23.9 · calibrated p 9e-4 ✓ | 20.4 EB05 18.2 · IC025 +4.1 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Reporting / coding artifact | serious n=217 · 100% clinician | not reported in cached trials |
| Hyperparathyroidism secondary | 358 | 22.1 19.8–24.7ROR 22.1 · calibrated p 0.001 ✓ | 19.1 EB05 17.4 · IC025 +4.0 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 9.5 (7.1–12.6) | Not in label — unassessed | serious n=357 | not reported in cached trials |
| Gouty arthritis | 111 | 21.7 17.8–26.6ROR 21.7 · calibrated p 0.001 ✓ | 18.7 EB05 16.0 · IC025 +3.8 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 7.6 (4.7–12.1) | Not in label — unassessed | serious n=107 · ♀ 0% (drug 35%) | NCT01101035: 1/3,098 (0.0%) on Allopurinol (serious AE) |
| Hyperphosphataemia | 295 | 21.7 19.2–24.5ROR 21.7 · calibrated p 0.001 ✓ | 18.7 EB05 17.0 · IC025 +4.0 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 22.2 (14.0–35.4) | Not in label — unassessed | serious n=294 · 100% clinician | not reported in cached trials |
| Chronic kidney disease-mineral and bone disorder | 140 | 20.1 16.8–24.0ROR 20.1 · calibrated p 0.002 ✓ | 17.5 EB05 15.2 · IC025 +3.8 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 13.4 (7.9–22.8) | Not in label — unassessed | serious n=140 | not reported in cached trials |
| Nephrogenic anaemia | 603 | 19.9 18.2–21.6ROR 19.9 · calibrated p 0.002 ✓ | 17.4 EB05 16.3 · IC025 +4.0 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 7.9 (6.5–9.7) | Likely indication confounding shares a disease stem with the indications wording | serious n=603 | not reported in cached trials |
| Gout | 2,255 | 19.2 18.4–20.1ROR 19.5 · calibrated p 0.002 ✓ | 16.9 EB05 16.3 · IC025 +4.0 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 4.5 (4.2–4.9) | Likely indication confounding term in indications; also in warnings | serious PRR 14.1 | NCT01101035: 6/3,092 (0.2%) on Allopurinol (serious AE) |
| Drug reaction with eosinophilia and systemic symptoms | 2,952 | 17.5 16.9–18.2ROR 17.8 · calibrated p 0.003 ✓ | 15.6 EB05 15.1 · IC025 +3.9 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 63.1 (49.6–80.4) | Labeled adverse reaction exact term | age-adj. PRR 16.5 · serious PRR 10.9 · 98% clinician | not reported in cached trials |
| Blood uric acid increased | 659 | 17.3 15.9–18.8ROR 17.4 · calibrated p 0.004 ✓ | 15.4 EB05 14.4 · IC025 +3.8 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 7.6 (6.3–9.2) | Likely indication confounding term in indications; also in warnings | serious n=564 | not reported in cached trials |
| Hyperuricaemia | 467 | 17.2 15.6–19.0ROR 17.3 · calibrated p 0.004 ✓ | 15.3 EB05 14.2 · IC025 +3.8 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 7.5 (6.0–9.4) | Likely indication confounding shares a disease stem with the indications wording | serious n=456 | not reported in cached trials |
| Blood phosphorus increased | 292 | 16.1 14.2–18.2ROR 16.1 · calibrated p 0.005 ✓ | 14.4 EB05 13.1 · IC025 +3.6 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 29.9 (17.5–51.1) | Lab value / disease marker | serious n=283 | not reported in cached trials |
| Tumour lysis syndrome | 860 | 14.6 13.6–15.7ROR 14.7 · calibrated p 0.008 ✓ | 13.3 EB05 12.5 · IC025 +3.6 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 9.5 (7.9–11.5) | Labeled adverse reaction exact term | serious PRR 9.3 · 92% clinician | not reported in cached trials |
| Rebound acid hypersecretion | 261 | 12.5 11.0–14.2ROR 12.5 · calibrated p 0.015 ✓ | 11.4 EB05 10.3 · IC025 +3.3 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 13.4 (9.0–19.7) | Not in label — unassessed | serious n=261 | not reported in cached trials |
| Drug rash with eosinophilia and systemic symptoms | 280 | 12.5 11.0–14.1ROR 12.5 · calibrated p 0.015 ✓ | 11.4 EB05 10.3 · IC025 +3.3 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Labeled (related wording) related wording | serious n=275 · 100% clinician | not reported in cached trials |
| Aortic valve stenosis | 146 | 11.9 10.1–14.1ROR 11.9 · calibrated p 0.018 ✓ | 10.9 EB05 9.5 · IC025 +3.1 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 17.4 (9.7–31.4) | Not in label — unassessed | serious n=145 · ♀ 0% (drug 35%) | NCT01101035: 4/3,092 (0.1%) on Allopurinol (serious AE) |
| Bronchial secretion retention | 102 | 11.8 9.6–14.4ROR 11.8 · calibrated p 0.019 ✓ | 10.7 EB05 9.0 · IC025 +3.0 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Not in label — unassessed | serious n=100 · ♀ 0% (drug 35%) | not reported in cached trials |
| Pulmonary function test abnormal | 125 | 11.7 9.7–14.0ROR 11.7 · calibrated p 0.020 ✓ | 10.7 EB05 9.1 · IC025 +3.1 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Reporting / coding artifact | serious n=124 · ♀ 0% (drug 35%) | not reported in cached trials |
| Systemic infection | 131 | 11.5 9.6–13.7ROR 11.5 · calibrated p 0.021 ✓ | 10.5 EB05 9.0 · IC025 +3.1 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 6.9 (4.6–10.5) | Not in label — unassessed | serious n=131 · ♀ 0% (drug 35%) · 100% clinician | not reported in cached trials |
| Toxic epidermal necrolysis (severe skin peeling reaction) | 1,170 | 11.3 10.6–12.0ROR 11.3 · calibrated p 0.021 ✓ | 10.4 EB05 10.0 · IC025 +3.3 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 28.4 (21.9–36.9) | Labeled adverse reaction exact term | age-adj. PRR 9.7 · serious PRR 7.3 · 94% clinician | not reported in cached trials |
| Cardioactive drug level increased | 99 | 10.8 8.8–13.2ROR 10.8 · calibrated p 0.026 ✓ | 9.9 EB05 8.3 · IC025 +2.9 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Lab value / disease marker | serious n=99 · 100% clinician | NCT01101035: 1/3,098 (0.0%) on Allopurinol (serious AE) |
| Dermatitis exfoliative generalised | 235 | 9.8 8.6–11.2ROR 9.8 · calibrated p 0.035 ✓ | 9.1 EB05 8.2 · IC025 +3.0 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 16.8 (10.7–26.6) | Labeled (related wording) related wording | serious n=235 · 100% clinician | not reported in cached trials |
| End stage renal disease | 1,153 | 8.9 8.4–9.5ROR 9.0 · calibrated p 0.046 ✓ | 8.4 EB05 8.0 · IC025 +3.0 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 9.1 (7.8–10.7) | Labeled (related wording) related wording | serious PRR 5.9 | NCT01101035: 2/3,092 (0.1%) on Allopurinol (serious AE) |
| Benign prostatic hyperplasia | 323 | 8.9 8.0–10.0ROR 8.9 · calibrated p 0.048 ✓ | 8.3 EB05 7.6 · IC025 +2.9 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 16.0 (10.9–23.3) | Not in label — unassessed | serious n=317 · ♀ 0% (drug 35%) | NCT01101035: 6/3,092 (0.2%) on Allopurinol (serious AE) |
| Cytokine release syndrome | 1,158 | 8.7 8.2–9.2ROR 8.7 · calibrated p 0.051 | 8.2 EB05 7.8 · IC025 +2.9 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 14.2 (11.7–17.1) | Not in label — unassessed | age-adj. PRR 7.7 · serious PRR 5.8 · 97% clinician | not reported in cached trials |
| Diastolic dysfunction | 178 | 8.2 7.0–9.5ROR 8.2 · calibrated p 0.064 | 7.6 EB05 6.7 · IC025 +2.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Not in label — unassessed | serious n=178 · ♀ 0% (drug 35%) | not reported in cached trials |
| Chronic lymphocytic leukaemia | 271 | 8.1 7.1–9.1ROR 8.1 · calibrated p 0.065 | 7.6 EB05 6.9 · IC025 +2.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 25.9 (15.4–43.5) | Likely indication confounding shares a disease stem with the indications wording | serious n=269 | not reported in cached trials |
| Neutropenic sepsis | 402 | 8.0 7.2–8.8ROR 8.0 · calibrated p 0.067 | 7.5 EB05 6.9 · IC025 +2.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Not in label — unassessed | serious PRR 5.3 · 92% clinician | not reported in cached trials |
| Aortic stenosis | 195 | 7.9 6.9–9.2ROR 8.0 · calibrated p 0.069 | 7.4 EB05 6.6 · IC025 +2.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: only this drug | Not in label — unassessed | serious n=195 · 100% clinician | NCT01101035: 4/3,092 (0.1%) on Allopurinol (serious AE) |
| Activated partial thromboplastin time prolonged | 282 | 7.9 7.0–8.9ROR 7.9 · calibrated p 0.070 | 7.4 EB05 6.7 · IC025 +2.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 31.1 (17.8–54.2) | Lab value / disease marker | serious n=278 · 100% clinician | not reported in cached trials |
| Iron deficiency | 239 | 7.6 6.7–8.7ROR 7.6 · calibrated p 0.078 | 7.2 EB05 6.4 · IC025 +2.6 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 28.5 (16.0–50.9) | Not in label — unassessed | serious n=231 | NCT01101035: 1/3,092 (0.0%) on Allopurinol (serious AE) |
| Splenomegaly | 610 | 7.4 6.8–8.0ROR 7.4 · calibrated p 0.085 | 7.0 EB05 6.5 · IC025 +2.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 23.0 (16.6–31.9) | Not in label — unassessed | age-adj. PRR 6.1 · serious PRR 4.7 | NCT01101035: 1/3,098 (0.0%) on Allopurinol (serious AE) |
| Anaemia macrocytic | 110 | 7.3 6.1–8.9ROR 7.3 · calibrated p 0.089 | 6.8 EB05 5.8 · IC025 +2.5 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 10.5 (6.1–18.0) | Not in label — unassessed | serious n=107 · ♀ 100% (drug 35%) · 100% clinician | not reported in cached trials |
| Hyperkalaemia (high potassium) | 1,806 | 7.3 7.0–7.7ROR 7.4 · calibrated p 0.085 | 7.0 EB05 6.7 · IC025 +2.7 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 11.4 (10.0–13.1) | Not in label — unassessed | age-adj. PRR 4.5 · serious PRR 5.0 | NCT01101035: 10/3,092 (0.3%) on Allopurinol (serious AE) |
| Stevens-johnson syndrome (severe blistering skin reaction) | 1,112 | 7.0 6.6–7.5ROR 7.1 · calibrated p 0.096 | 6.7 EB05 6.4 · IC025 +2.6 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 21.8 (17.2–27.6) | Labeled adverse reaction exact term | age-adj. PRR 7.4 · serious PRR 4.7 | NCT01101035: 1/3,092 (0.0%) on Allopurinol (serious AE) |
Clinical concept groups
MedDRA splits one clinical problem across several terms (e.g. "neutropenia", "neutrophil count decreased", "agranulocytosis"), which dilutes term-level signals. These rows count reports with any term in a concept group (an exact union, not a sum), compared with all other drugs. Groups are hand-built and listed in the methods.
| Concept | Reports | PRR 95% CI | Reading |
|---|---|---|---|
| Severe cutaneous reaction | 5,296 | 10.310.0–10.6 | signal |
| Kidney injury | 16,247 | 4.94.9–5.0 | signal |
| Anaemia | 8,332 | 3.83.7–3.9 | signal |
| Hyponatraemia | 2,168 | 3.73.6–3.9 | signal |
| Neutropenia / agranulocytosis | 6,526 | 3.63.5–3.7 | signal |
| Thrombocytopenia | 5,662 | 3.53.4–3.6 | signal |
| Heart failure | 4,290 | 3.33.2–3.4 | signal |
| Gi bleeding | 4,091 | 3.13.0–3.2 | signal |
| Arrhythmia / qt | 4,179 | 3.02.9–3.0 | signal |
| Rhabdomyolysis / myopathy | 1,561 | 2.62.5–2.8 | signal |
| Serious infection | 12,940 | 2.32.2–2.3 | signal |
| Interstitial lung disease | 1,447 | 2.11.9–2.2 | raised |
| Liver injury | 4,490 | 2.02.0–2.1 | raised |
| Pancreatitis | 1,158 | 2.01.8–2.1 | raised |
| Hypoglycaemia | 1,318 | 1.91.8–2.0 | raised |
| Fall / fracture | 4,913 | 1.81.7–1.8 | raised |
Trial evidence (ClinicalTrials.gov)
✓ Trial adverse-event data found on ClinicalTrials.gov
Largest completed trials with posted results that list Allopurinol 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 (13 of 40 signal terms matched).
- NCT01101035 — Cardiovascular Safety of Febuxostat and Allopurinol in Participants With Gout and Cardiovascular Comorbidities (N=6198, PHASE3; 857 AE terms posted; arms: Febuxostat; Allopurinol)
- NCT00430248 — Efficacy and Safety of Oral Febuxostat in Participants With Gout (N=2269, PHASE3; 59 AE terms posted; arms: Febuxostat 40 mg QD; Febuxostat 80 mg QD; Allopurinol 200 mg or 300 mg QD)
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 |
|---|---|---|---|---|---|---|
| Diarrhoea (diarrhea) | 8,697 | 1.8 1.8–1.9ROR 1.9 · calibrated p 0.879 | 1.8 EB05 1.8 · IC025 +0.8 vs other Xanthine Oxidase Inhibitors: PRR 14.1 (13.2–15.1) | Labeled adverse reaction exact term | age-adj. PRR 1.5 · serious PRR 1.7 | NCT01101035: 4/3,092 (0.1%) on Allopurinol (serious AE) |
| Fatigue (tiredness) | 8,251 | 1.4 1.4–1.5ROR 1.5 · calibrated p 0.616 | 1.4 EB05 1.4 · IC025 +0.5 vs other Xanthine Oxidase Inhibitors: PRR 19.1 (17.6–20.7) | Labeled (related wording) related wording | age-adj. PRR 1.2 · serious PRR 1.4 | NCT01101035: 2/3,098 (0.1%) on Allopurinol (serious AE) |
| Dyspnoea (shortness of breath) | 7,905 | 1.9 1.9–1.9ROR 1.9 · calibrated p 0.914 | 1.9 EB05 1.9 · IC025 +0.9 vs other Xanthine Oxidase Inhibitors: PRR 17.7 (16.3–19.1) | Not in label — unassessed | age-adj. PRR 1.6 · serious PRR 1.6 | NCT01101035: 21/3,092 (0.7%) on Allopurinol (serious AE) |
| Nausea | 7,310 | 1.3 1.2–1.3ROR 1.3 · calibrated p 0.484 | 1.2 EB05 1.2 · IC025 +0.3 vs other Xanthine Oxidase Inhibitors: PRR 12.2 (11.4–13.1) | Labeled adverse reaction exact term | age-adj. PRR 1.2 · serious PRR 1.3 | NCT01101035: 4/3,092 (0.1%) on Allopurinol (serious AE) |
| Death | 6,884 | 1.1 1.1–1.1ROR 1.1 · calibrated p 0.361 | 1.1 EB05 1.1 · IC025 +0.1 vs other Xanthine Oxidase Inhibitors: PRR 18.8 (17.2–20.5) | Outcome field, not a reaction | age-adj. PRR 0.8 · serious PRR 0.8 | NCT01101035: 1/3,092 (0.0%) on Allopurinol (serious AE) |
| Acute kidney injury (sudden kidney damage) | 6,743 | 6.2 6.1–6.4ROR 6.4 · calibrated p 0.124 | 6.0 EB05 5.9 · IC025 +2.5 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 11.3 (10.5–12.1) | Labeled adverse reaction exact term | age-adj. PRR 4.2 · serious PRR 4.2 | NCT01101035: 132/3,092 (4.3%) on Allopurinol (serious AE) |
| Off label use (used outside approved label) | 6,644 | 1.0 1.0–1.1ROR 1.0 · calibrated p 0.329 | 1.0 EB05 1.0 · IC025 +0.0 vs other Xanthine Oxidase Inhibitors: PRR 12.7 (11.8–13.6) | Reporting / coding artifact | age-adj. PRR 1.0 · serious PRR 1.1 | not reported in cached trials |
| Pyrexia (fever) | 6,075 | 2.4 2.3–2.5ROR 2.4 · calibrated p 0.836 | 2.4 EB05 2.3 · IC025 +1.2 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 15.6 (14.4–17.0) | Labeled (related wording) related wording | age-adj. PRR 2.3 · serious PRR 2.0 | NCT01101035: 3/3,092 (0.1%) on Allopurinol (serious AE) |
| Pneumonia (lung infection) | 5,708 | 2.4 2.3–2.5ROR 2.5 · calibrated p 0.830 | 2.4 EB05 2.3 · IC025 +1.2 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 14.7 (13.5–16.0) | Not in label — unassessed | age-adj. PRR 1.8 · serious PRR 1.7 | NCT01101035: 3/3,092 (0.1%) on Allopurinol (serious AE) |
| Asthenia (weakness) | 5,627 | 2.0 2.0–2.1ROR 2.1 · calibrated p 0.983 | 2.0 EB05 2.0 · IC025 +1.0 vs other Xanthine Oxidase Inhibitors: PRR 23.8 (21.4–26.6) | Labeled adverse reaction exact term | age-adj. PRR 1.5 · serious PRR 1.7 | NCT01101035: 8/3,092 (0.3%) on Allopurinol (serious AE) |
| Anaemia (low red blood cells) | 5,454 | 3.9 3.8–4.0ROR 4.0 · calibrated p 0.369 | 3.9 EB05 3.8 · IC025 +1.9 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 13.3 (12.2–14.4) | Labeled adverse reaction exact term | age-adj. PRR 2.9 · serious PRR 2.9 | NCT01101035: 1/3,092 (0.0%) on Allopurinol (serious AE) |
| Drug ineffective (drug did not work) | 5,135 | 0.5 0.5–0.5ROR 0.5 · calibrated p 0.051 | 0.5 EB05 0.5 · IC025 -1.0 PRR-only: not supported by EBGM or IC vs other Xanthine Oxidase Inhibitors: PRR 10.5 (9.7–11.3) | Reporting / coding artifact | age-adj. PRR 0.6 · serious PRR 0.7 | not reported in cached trials |
| Dizziness | 5,104 | 1.4 1.3–1.4ROR 1.4 · calibrated p 0.575 | 1.4 EB05 1.4 · IC025 +0.4 vs other Xanthine Oxidase Inhibitors: PRR 19.0 (17.2–21.1) | Labeled adverse reaction exact term | age-adj. PRR 1.2 · serious PRR 1.3 | NCT01101035: 4/3,092 (0.1%) on Allopurinol (serious AE) |
| Renal failure (kidney failure) | 4,745 | 4.9 4.8–5.1ROR 5.0 · calibrated p 0.229 | 4.8 EB05 4.7 · IC025 +2.2 3/3 methods agree vs other Xanthine Oxidase Inhibitors: PRR 14.6 (13.3–16.1) | Labeled adverse reaction exact term | age-adj. PRR 3.6 · serious PRR 3.4 | NCT01101035: 19/3,092 (0.6%) on Allopurinol (serious AE) |
| Fall | 4,662 | 1.9 1.9–2.0ROR 1.9 · calibrated p 0.906 | 1.9 EB05 1.8 · IC025 +0.9 vs other Xanthine Oxidase Inhibitors: PRR 18.0 (16.3–20.0) | Not in label — unassessed | age-adj. PRR 1.2 · serious PRR 1.5 | NCT01101035: 13/3,092 (0.4%) on Allopurinol (serious AE) |
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.
- Appendicolith — n=301, PRR 537.3
- Hyperparathyroidism secondary — n=358, PRR 22.1
- Gouty arthritis — n=111, PRR 21.7 (also seen in trial arm)
- Hyperphosphataemia — n=295, PRR 21.7
- Chronic kidney disease-mineral and bone disorder — n=140, PRR 20.1
- Rebound acid hypersecretion — n=261, PRR 12.5
- Aortic valve stenosis — n=146, PRR 11.9 (also seen in trial arm)
- Bronchial secretion retention — n=102, PRR 11.8
- Systemic infection — n=131, PRR 11.5
- Benign prostatic hyperplasia — n=323, PRR 8.9 (also seen in trial arm)
✓ A hand-written Bradford Hill causality assessment exists for this drug: Allopurinol ↔ DRESS syndrome (drug reaction with eosinophilia and systemic symptoms).
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 Allopurinol?
In FDA FAERS, the most frequently co-reported reaction terms for Allopurinol are diarrhoea, fatigue, dyspnoea, nausea, acute kidney injury, 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 Allopurinol have an FDA boxed warning?
No. The FDA label retrieved for Allopurinol has no boxed warning; see the label's Warnings and Precautions for the recognised risks.
Do FAERS signals prove that Allopurinol 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 0780dc78-d287-d5db-e063-6294a90aa1dd, effective 20250109; matched on
openfda.generic_name.exact:"ALLOPURINOL" AND openfda.product_type:"HUMAN PRESCRIPTION DRUG") - PubChem CID 135401907 description (ChEBI)
- 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, 1,198 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
ALLOPURINOL, results-bearing studies sorted by enrollment)
Page generated 2026-10-14. 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.