Allopurinol Sodium side effects: what 554 FDA adverse event reports show

Allopurinol Sodium · 31 reaction terms · 345 drug–reaction co-reports · data 2026-09-14

Drug class

Xanthine Oxidase Inhibitor

FDA label (Established Pharmacologic Class) · compare the class

Who reports

554 reports · 86% serious · 90 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

11. DESCRIPTION Allopurinol is a xanthine oxidase inhibitor. It has the following structural formula: Allopurinol is known chemically as 1, 5-dihydro-4 H -pyrazolo [3, 4-d]pyrimidin-4-one. and it has a molecular weight of 136.11 g/mol.

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 15 strongest signals

Labeled adverse reaction 1Labeled (related wording) 2Likely indication confounding 1Reporting / coding artifact 2Lab value / disease marker 2Not in label — unassessed 7

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 flags pairs whose reports are unusually skewed by sex or come mostly from consumers rather than clinicians. 16 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
Incorrect route of product administration	25	56.4 38.4–82.7ROR 59.0 · χ² 1,304 / p 6e-286	54.1 EB05 38.5 · IC025 +4.1 3/3 methods agree	Reporting / coding artifact	serious PRR 75.2 · ♀ 67% (drug 35%) · 96% clinician	no trial data cached
Full blood count abnormal	11	39.5 22.0–71.0ROR 40.3 · χ² 375 / p 7e-84	37.2 EB05 22.1 · IC025 +2.9 3/3 methods agree	Lab value / disease marker	serious PRR 35.1	no trial data cached
Cardiomegaly	11	33.6 18.7–60.3ROR 34.2 · χ² 316 / p 6e-71	31.9 EB05 18.9 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious PRR 23.0	no trial data cached
Gout	15	31.6 19.2–52.1ROR 32.5 · χ² 415 / p 2e-92	30.5 EB05 19.6 · IC025 +3.1 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 29.8	no trial data cached
Hyperlipidaemia	10	31.6 17.1–58.4ROR 32.2 · χ² 266 / p 3e-60	29.9 EB05 17.2 · IC025 +2.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 23.3	no trial data cached
Middle insomnia	15	30.5 18.5–50.3ROR 31.4 · χ² 400 / p 3e-89	29.5 EB05 18.9 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 44.5	no trial data cached
Body temperature increased	16	29.6 18.3–48.0ROR 30.5 · χ² 414 / p 2e-92	28.7 EB05 18.7 · IC025 +3.1 3/3 methods agree	Lab value / disease marker	serious PRR 24.4	no trial data cached
Rib fracture	16	29.5 18.2–47.9ROR 30.4 · χ² 413 / p 4e-92	28.6 EB05 18.6 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 21.5	no trial data cached
Poor quality sleep	15	26.5 16.1–43.7ROR 27.3 · χ² 344 / p 5e-77	25.7 EB05 16.5 · IC025 +3.0 3/3 methods agree	Reporting / coding artifact	serious PRR 32.7	no trial data cached
Muscle twitching	16	26.2 16.2–42.5ROR 27.0 · χ² 363 / p 3e-81	25.5 EB05 16.6 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 25.6	no trial data cached
Sedation	16	23.2 14.3–37.7ROR 23.9 · χ² 319 / p 1e-71	22.6 EB05 14.6 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 20.1	no trial data cached
End stage renal disease	11	22.6 12.6–40.6ROR 23.1 · χ² 206 / p 5e-47	21.6 EB05 12.4 · IC025 +2.5 3/3 methods agree	Labeled (related wording) related wording	serious PRR 15.1	no trial data cached
Nightmare	16	17.4 10.8–28.3ROR 17.9 · χ² 232 / p 1e-52	16.8 EB05 10.5 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 19.8	no trial data cached
Renal failure acute	19	16.7 10.7–26.0ROR 17.3 · χ² 266 / p 5e-60	16.2 EB05 10.6 · IC025 +2.8 3/3 methods agree	Labeled (related wording) related wording	serious PRR 11.3	no trial data cached
Lower respiratory tract infection	20	16.7 10.9–25.7ROR 17.3 · χ² 280 / p 3e-63	16.2 EB05 10.8 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious PRR 11.8 · 100% clinician	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
Incorrect route of product administration	25	56.4 38.4–82.7ROR 59.0 · χ² 1,304 / p 6e-286	54.1 EB05 38.5 · IC025 +4.1 3/3 methods agree	Reporting / coding artifact	serious PRR 75.2 · ♀ 67% (drug 35%) · 96% clinician	no trial data cached
Lower respiratory tract infection	20	16.7 10.9–25.7ROR 17.3 · χ² 280 / p 3e-63	16.2 EB05 10.8 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious PRR 11.8 · 100% clinician	no trial data cached
Renal failure acute	19	16.7 10.7–26.0ROR 17.3 · χ² 266 / p 5e-60	16.2 EB05 10.6 · IC025 +2.8 3/3 methods agree	Labeled (related wording) related wording	serious PRR 11.3	no trial data cached
Nightmare	16	17.4 10.8–28.3ROR 17.9 · χ² 232 / p 1e-52	16.8 EB05 10.5 · IC025 +2.7 3/3 methods agree	Not in label — unassessed	serious PRR 19.8	no trial data cached
Sedation	16	23.2 14.3–37.7ROR 23.9 · χ² 319 / p 1e-71	22.6 EB05 14.6 · IC025 +3.0 3/3 methods agree	Not in label — unassessed	serious PRR 20.1	no trial data cached
Muscle twitching	16	26.2 16.2–42.5ROR 27.0 · χ² 363 / p 3e-81	25.5 EB05 16.6 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 25.6	no trial data cached
Rib fracture	16	29.5 18.2–47.9ROR 30.4 · χ² 413 / p 4e-92	28.6 EB05 18.6 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 21.5	no trial data cached
Body temperature increased	16	29.6 18.3–48.0ROR 30.5 · χ² 414 / p 2e-92	28.7 EB05 18.7 · IC025 +3.1 3/3 methods agree	Lab value / disease marker	serious PRR 24.4	no trial data cached
Poor quality sleep	15	26.5 16.1–43.7ROR 27.3 · χ² 344 / p 5e-77	25.7 EB05 16.5 · IC025 +3.0 3/3 methods agree	Reporting / coding artifact	serious PRR 32.7	no trial data cached
Middle insomnia	15	30.5 18.5–50.3ROR 31.4 · χ² 400 / p 3e-89	29.5 EB05 18.9 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 44.5	no trial data cached
Gout	15	31.6 19.2–52.1ROR 32.5 · χ² 415 / p 2e-92	30.5 EB05 19.6 · IC025 +3.1 3/3 methods agree	Likely indication confounding term in indications; also in warnings	serious PRR 29.8	no trial data cached
End stage renal disease	11	22.6 12.6–40.6ROR 23.1 · χ² 206 / p 5e-47	21.6 EB05 12.4 · IC025 +2.5 3/3 methods agree	Labeled (related wording) related wording	serious PRR 15.1	no trial data cached
Cardiomegaly	11	33.6 18.7–60.3ROR 34.2 · χ² 316 / p 6e-71	31.9 EB05 18.9 · IC025 +2.8 3/3 methods agree	Not in label — unassessed	serious PRR 23.0	no trial data cached
Full blood count abnormal	11	39.5 22.0–71.0ROR 40.3 · χ² 375 / p 7e-84	37.2 EB05 22.1 · IC025 +2.9 3/3 methods agree	Lab value / disease marker	serious PRR 35.1	no trial data cached
Hyperlipidaemia	10	31.6 17.1–58.4ROR 32.2 · χ² 266 / p 3e-60	29.9 EB05 17.2 · IC025 +2.6 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 23.3	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.

Lower respiratory tract infection — n=20, PRR 16.7

✓ 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 lower respiratory tract infection, renal failure acute, nightmare, sedation, muscle twitching, rib fracture. 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")
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, 31 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.