What the label lists and what reports show
Propafenone side effects
Propafenone's FDA label: “The most commonly reported adverse events with propafenone (greater than 5%) included: unusual taste, nausea and/or vomiting, dizziness, constipation, headache, fatigue, first-degree AV block, and intraventricular conduction delay.” FAERS holds 4,209 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 dizziness (264 reports).
- Generic listed
- Boxed warning
Check it at the source: the propafenone FDA label on DailyMed (effective September 1, 2025, Strides Pharma Science Limited); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are possible side effects of propafenone hydrochloride tablets?Propafenone hydrochloride tablets can cause serious side effects including: New or worsened abnormal heart beats that can cause sudden death or be life-threatening. Your doctor may do an electrocardiogram (ECG or EKG) before and during treatment to check your heart for these problems. New or worsened heart failure. Tell your doctor about any changes in your heart symptoms, including: any new or increased swelling in your arms or legs trouble breathing sudden weight gain Effects on pacemaker function. Propafenone hydrochloride tablets may affect how an implanted pacemaker or defibrillator works. Your doctor should check how your pacemaker or defibrillator is working during and after treatment with propafenone hydrochloride tablets. They may need to be re-programmed. Very low white blood cell levels in your blood (agranulocytosis). […]
Source: FDA drug label, Strides Pharma Science Limited, effective September 1, 2025 (SPL set c65253ab-937f-4982-b841-69c2b9f9ccdb), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe most commonly reported adverse events with propafenone (greater than 5%) included: unusual taste, nausea and/or vomiting, dizziness, constipation, headache, fatigue, first-degree AV block, and intraventricular conduction delay.
Table 1: Adverse Reactions Reported for > 1.5% of Subjects with Supraventricular Tachycardia
| Adverse Reactions | Incidence (N = 480) | % of Subjects Who Discontinued |
|---|---|---|
| Unusual Taste | 14% | 1.3% |
| Nausea and/or Vomiting | 11% | 2.9% |
| Dizziness | 9% | 1.7% |
| Constipation | 8% | 0.2% |
| Headache | 6% | 0.8% |
| Fatigue | 6% | 1.5% |
| Blurred Vision | 3% | 0.6% |
| Weakness | 3% | 1.3% |
| Dyspnea | 2% | 1.0% |
| Wide Complex Tachycardia | 2% | 1.9% |
| CHF | 2% | 0.6% |
| Bradycardia | 2% | 0.2% |
| Palpitations | 2% | 0.2% |
| Tremor | 2% | 0.4% |
| Anorexia | 2% | 0.2% |
| Diarrhea | 2% | 0.4% |
| Ataxia | 2% | 0.0% |
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, continuedThe most commonly reported adverse events with propafenone (greater than 5%) included: unusual taste, nausea and/or vomiting, dizziness, constipation, headache, fatigue, first-degree AV block, and intraventricular conduction delay. (6.1) To report SUSPECTED ADVERSE REACTIONS, contact Strides Pharma Inc 1-877-244-9825 or go to www.strides.com or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice. Adverse reactions associated with propafenone hydrochloride occur most frequently in the gastrointestinal, cardiovascular, and central nervous systems. About 20% of subjects treated with propafenone hydrochloride have discontinued treatment because of adverse reactions. Adverse reactions reported for greater than 1.5% of 474 subjects with SVT who received propafenone hydrochloride in U.S. clinical trials are presented in Table 1 by incidence and percent discontinuation, reported to the nearest percent.
Source: FDA drug label, Strides Pharma Science Limited, effective September 1, 2025 (SPL set c65253ab-937f-4982-b841-69c2b9f9ccdb), via openFDA; the full label on DailyMed
What do FAERS reports show?
4,209 reports list propafenone among the medicines taken, each a report of something that happened, not proof the medicine caused it; 504 are coded as a death and 1,803 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 19 reactions below, 12 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.
Reports received each year
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?
- Propafenone: 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