What the label lists and what reports show
Quinidine side effects
Quinidine's FDA label: “The adverse reactions most frequently reported have consistently been gastrointestinal, including diarrhea, nausea, vomiting, and heartburn/esophagitis.” FAERS holds 208 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is fatigue (23 reports).
- Generic listed
- Boxed warning
Check it at the source: the quinidine FDA label on DailyMed (effective February 1, 2018, Sun Pharmaceutical Industries, Inc.); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe adverse reactions most frequently reported have consistently been gastrointestinal, including diarrhea, nausea, vomiting, and heartburn/esophagitis.
A table the label prints in its adverse reactions section without a title; its column headings name the groups compared
This table is printed in the QUINIDINE SULFATE label published by EPIC PHARMA, LLC of November 8, 2023; the label quoted above does not print one.
| Reaction | Adverse Experiences in a 245-Patient PVC Trial Incidence (%) Incidence (%) |
|---|---|
| diarrhea | 85 (35) |
| “upper gastrointestinal distress” | 55 (22) |
| lightheadedness | 37 (15) |
| headache | 18 (7) |
| fatigue | 17 (7) |
| palpitations | 16 (7) |
| angina-like pain | 14 (6) |
| weakness | 13 (5) |
| rash | 11 (5) |
| visual problems | 8 (3) |
| change in sleep habits | 7 (3) |
| tremor | 6 (2) |
| nervousness | 5 (2) |
| discoordination | 3 (1) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedQuinidine preparations have been used for many years, but there are only sparse data from which to estimate the incidence of various adverse reactions. The adverse reactions most frequently reported have consistently been gastrointestinal, including diarrhea, nausea, vomiting, and heartburn/esophagitis. In the reported study that was closest in character to the predominant approved use of quinidine gluconate, 86 adult outpatients with atrial fibrillation were followed for six months while they received slow-release quinidine bisulfate tablets, 600 mg (approximately 400 mg of quinidine base) twice daily. The incidences of adverse experiences reported more than once were as shown in the table below. The most serious quinidine-associated adverse reactions are described above under WARNINGS . ADVERSE EXPERIENCES REPORTED MORE THAN ONCE IN 86 PATIENTS WITH ATRIAL FIBRILLATION Incidence (%) diarrhea 21 (24%) fever 5 (6%) rash 5 (6%) arrhythmia 3 (3%) abnormal electrocardiogram 3 (3%) nausea/vomiting 3 (3%) dizziness 3 (3%) headache 3 (3%) asthenia 2 (2%) cerebral ischemia 2 (2%) Vomiting and diarrhea can occur as isolated reactions to therapeutic levels of quinidine, but they may also be the first signs of cinchonism, a syndrome that may also include tinnitus, reversible high-frequency hearing loss, deafness, vertigo, blurred vision, diplopia, photophobia, headache, confusion, and …
Source: FDA drug label, Sun Pharmaceutical Industries, Inc., effective February 1, 2018 (SPL set 5023f053-fcc4-4c2c-aa59-9ec198ad185e), via openFDA; the full label on DailyMed
What do FAERS reports show?
208 reports list quinidine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 18 are coded as a death and 75 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 23 reactions below, 3 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Quinidine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions