Drug · FAERS side-effect profile with label screen

Quinidine side effects: what 143 FDA adverse event reports show

Quinidine Sulfate Tablet · 6 reaction terms · 76 drug–reaction co-reports · data 2026-09-14

Drug class

Not stated in label

Label matched

Quinidine Sulfate Tablet (Quinidine Sulfate)

closest FDA label found for this product string; brand list suppressed because the label is a related product, not an exact match

Who reports

143 reports · 78% serious · 11 with death outcome · 52% female

openFDA FAERS counts, all years, deduplication not applied

Used for

Conversion of Atrial Fibrillation/Flutter In patients with symptomatic atrial fibrillation/flutter whose symptoms are not adequately controlled by measures that reduce the rate of ventricular response, quinidine sulfate is indicated as a means of restoring normal sinus rhythm.

FDA label, Indications and Usage

What it is

DESCRIPTION Quinidine is an antimalarial schizonticide and an antiarrhythmic agent with class 1A activity; it is the d-isomer of quinine, and its molecular weight is 324.43. Quinidine sulfate .

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 6 strongest signals

Labeled adverse reaction 1Labeled (related wording) 1Likely indication confounding 1Not in label — unassessed 3

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.
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. 0 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
Photosensitivity reaction (sun sensitivity)	12	107.0 62.2–183.9ROR 116.7 · χ² 1,156 / p 9e-254	91.8 EB05 55.9 · IC025 +3.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 124.5	no trial data cached
Peritonitis	13	92.1 54.8–154.7ROR 101.2 · χ² 1,082 / p 1e-237	81.4 EB05 50.6 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 67.8	no trial data cached
Intervertebral disc protrusion	13	87.0 51.8–146.1ROR 95.6 · χ² 1,021 / p 2e-224	77.4 EB05 48.2 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious PRR 74.7	no trial data cached
Frequent bowel movements	12	65.4 38.1–112.5ROR 71.3 · χ² 699 / p 3e-154	59.5 EB05 36.3 · IC025 +3.2 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 74.2	no trial data cached
Systemic lupus erythematosus	13	53.9 32.1–90.5ROR 59.2 · χ² 624 / p 5e-138	50.2 EB05 31.2 · IC025 +3.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 40.6	no trial data cached
Colitis ulcerative	13	42.8 25.5–71.8ROR 46.9 · χ² 490 / p 7e-109	40.4 EB05 25.1 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 33.8	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
Colitis ulcerative	13	42.8 25.5–71.8ROR 46.9 · χ² 490 / p 7e-109	40.4 EB05 25.1 · IC025 +3.1 3/3 methods agree	Not in label — unassessed	serious PRR 33.8	no trial data cached
Systemic lupus erythematosus	13	53.9 32.1–90.5ROR 59.2 · χ² 624 / p 5e-138	50.2 EB05 31.2 · IC025 +3.2 3/3 methods agree	Labeled adverse reaction exact term	serious PRR 40.6	no trial data cached
Intervertebral disc protrusion	13	87.0 51.8–146.1ROR 95.6 · χ² 1,021 / p 2e-224	77.4 EB05 48.2 · IC025 +3.4 3/3 methods agree	Not in label — unassessed	serious PRR 74.7	no trial data cached
Peritonitis	13	92.1 54.8–154.7ROR 101.2 · χ² 1,082 / p 1e-237	81.4 EB05 50.6 · IC025 +3.5 3/3 methods agree	Not in label — unassessed	serious PRR 67.8	no trial data cached
Frequent bowel movements	12	65.4 38.1–112.5ROR 71.3 · χ² 699 / p 3e-154	59.5 EB05 36.3 · IC025 +3.2 3/3 methods agree	Likely indication confounding shares a disease stem with the indications wording	serious PRR 74.2	no trial data cached
Photosensitivity reaction (sun sensitivity)	12	107.0 62.2–183.9ROR 116.7 · χ² 1,156 / p 9e-254	91.8 EB05 55.9 · IC025 +3.4 3/3 methods agree	Labeled (related wording) related wording	serious PRR 124.5	no trial data cached

Unlabeled candidate signals

Every screened signal with n ≥ 20 was either labeled, an indication term, or an artifact pattern — no unlabeled candidate stood out in the top signals.

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 Quinidine?

In FDA FAERS, the most frequently co-reported reaction terms for Quinidine are colitis ulcerative, systemic lupus erythematosus, intervertebral disc protrusion, peritonitis, frequent bowel movements, photosensitivity reaction. 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 Quinidine have an FDA boxed warning?

No. The FDA label retrieved for Quinidine has no boxed warning; see the label's Warnings and Precautions for the recognised risks.

Do FAERS signals prove that Quinidine 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 b0d6341b-d880-4f0b-8844-bc788c03004a, effective 20231108; matched on openfda.generic_name.exact:"QUINIDINE SULFATE TABLET")
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, 6 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.