From the Guidelines
Flecainide can cause several side effects, including ventricular tachycardia, congestive heart failure, and enhanced AV nodal conduction, and should be used with caution in patients with structural heart disease. The most common side effects of flecainide include:
- Dizziness
- Visual disturbances like blurred vision or seeing spots
- Headache
- Nausea
- Fatigue
- Tremors Some patients may experience more serious side effects, such as:
- New or worsening heart rhythm problems
- Signs of heart failure, including swelling in ankles/feet, unusual tiredness, and shortness of breath
- Fainting or severe dizziness Flecainide can also cause a dangerous condition called proarrhythmia, where it paradoxically worsens heart rhythm problems, particularly in patients with structural heart disease 1. This medication may interact with many other drugs, so it's essential to inform your doctor about all medications you're taking. Regular monitoring with ECGs and blood tests is typically required while on flecainide 1. The side effects occur because flecainide works by slowing electrical conduction in the heart, which can affect other electrically active tissues in the body like the brain and nervous system. If you experience concerning side effects while taking flecainide, contact your healthcare provider immediately rather than stopping the medication abruptly.
It's also important to note that flecainide should be used with caution in patients with certain conditions, such as:
- Structural heart disease, including ischemic heart disease
- Atrial flutter with 1:1 AV conduction
- QT prolongation
- Torsades de pointes
- Worsening heart failure
- Bradycardia
- Sinus or AV conduction disease
- Cardiogenic shock
- Brugada syndrome
- Renal dysfunction
- Hepatic dysfunction
- QT-prolonging drugs
- Amiodarone, digoxin, ritonavir, saquinavir, tipranavir 1.
Overall, flecainide can be an effective medication for treating certain heart rhythm disorders, but it's essential to carefully weigh the potential benefits and risks and to closely monitor patients for any signs of adverse effects.
From the FDA Drug Label
In patients treated with flecainide for sustained VT, 80% (51/64) of proarrhythmic events occurred within 14 days of the onset of therapy. New or worsened CHF occurred in 6.3% of 1046 patients with PVCs, non-sustained or sustained VT. Of 297 patients with sustained VT, 9.1% experienced new or worsened CHF. New or worsened CHF was reported in 0. 4% of 225 patients with supraventricular arrhythmias. There have also been instances of second- (0.5%) or third-degree (0.4%) AV block. Patients have developed sinus bradycardia, sinus pause, or sinus arrest, about 1. 2% altogether. The frequency of most of these serious adverse events probably increases with higher trough plasma levels, especially when these trough levels exceed 1 mcg/mL. Table 1: Most Common Non-Cardiac Effects in Ventricular Arrhythmia Patients Treated with Flecainide in the Multicenter Study
- Dizziness includes reports of dizziness, lightheadedness, faintness, unsteadiness, near syncope, etc. † Visual disturbance includes reports of blurred vision, difficulty in focusing, spots before eyes, etc Adverse Effect Incidence All 429 Patients at Any Dose Incidence by Dose During Upward Titration 200 mg/Day (N=426) 300 mg/Day (N=293) 400 mg/Day (N=100) Dizziness* 18.9% 11.0% 10.6% 13.0% Visual Disturbances† 15.9% 5.4% 12.3% 18.0% Dyspnea 10.3% 5.2% 7.5% 4.0% Headache 9.6% 4.5% 6.1% 9.0% Nausea 8.9% 4.9% 4.8% 6.0% Fatigue 7.7% 4.5% 4.4% 3.0% Palpitation 6.1% 3.5% 2.4% 7.0% Chest Pain 5.4% 3.1% 3. 8% 1.0% Asthenia 4.9% 2.6% 2.0% 4.0% Tremor 4.7% 2.4% 3.4% 2.0% Constipation 4.4% 2.8% 2.1% 1.0% Edema 3.5% 1.9% 1.4% 2.0% Abdominal Pain 3.3% 1.9% 2.4% 1. 0%
The side effects of Flecainide include:
- Proarrhythmic events: 13% incidence in patients with sustained VT, with 80% of events occurring within 14 days of therapy initiation 2
- Cardiac effects: new or worsened CHF (6.3% of patients with PVCs, non-sustained or sustained VT), second- or third-degree AV block (0.5% and 0.4%, respectively), sinus bradycardia, sinus pause, or sinus arrest (1.2% altogether) 2
- Non-cardiac effects:
From the Research
Side Effects of Flecainide
The side effects of flecainide can be categorized into several groups, including:
- Extracardiac adverse effects, such as dizziness, visual disturbances, headache, nausea, dyspnea, and chest pain, which were reported in a study published in The American Journal of Cardiology in 1984 3
- Cardiac side effects, including ventricular tachyarrhythmias, severe bradycardia, and cardiogenic shock, which can be life-threatening, as reported in a case study published in The Journal of Emergency Medicine in 2020 4
- Electrocardiographic changes, such as prolongation of the PR and QRS intervals, which can indicate toxicity, as reported in a study published in Annals of Internal Medicine in 1987 5
Common Side Effects
The most frequently reported side effects of flecainide include:
- Dizziness (30%) and visual disturbances (28%), which often occur together 3
- Headache, nausea, dyspnea, and chest pain, which occur at incidences of 6 to 9% 3
- Other adverse experiences, which occur at incidences of greater than or equal to 5% 3
Serious Side Effects
Flecainide can cause serious side effects, including:
- Cardiac arrest, dysrhythmias, and heart failure, as reported in a case study published in The Journal of Emergency Medicine in 2020 4
- Ventricular tachyarrhythmias and severe bradycardia, which can be life-threatening, as reported in a study published in Annals of Internal Medicine in 1987 5
- Acute kidney injury (AKI) resulting in flecainide accumulation, which can be high risk for missed diagnosis in the emergency department, as reported in a case study published in The Journal of Emergency Medicine in 2020 4
Special Considerations
Flecainide should be used with caution in patients with certain medical conditions, such as: