Flecainide Side Effects
Flecainide carries significant cardiac risks including proarrhythmic effects, conduction abnormalities, and heart failure exacerbation, with the most common non-cardiac side effects being dizziness (18.9%) and visual disturbances (15.9%). 1
Serious Cardiac Side Effects
Proarrhythmic Effects
- New or worsened ventricular arrhythmias occur in 7-13% of patients, with 80% of proarrhythmic events occurring within the first 14 days of therapy 1
- Atrial flutter with 1:1 AV conduction can develop, potentially leading to dangerously rapid ventricular rates 2
- Ventricular tachycardia and ventricular fibrillation (cardiac arrest) have been reported, with some cases being unresuscitatable 1
- In post-MI patients with asymptomatic PVCs, flecainide was associated with a 5.1% rate of death and non-fatal cardiac arrest versus 2.3% with placebo 1
Conduction Abnormalities
- Second-degree AV block occurs in 0.5% and third-degree AV block in 0.4% of patients 1
- Sinus bradycardia, sinus pause, or sinus arrest develop in approximately 1.2% of patients 1
- QRS complex widening and PR interval prolongation are expected pharmacologic effects 2
Heart Failure
- New or worsened congestive heart failure occurs in 6.3% of patients with ventricular arrhythmias and 9.1% of those with sustained VT 1
- CHF was reported in only 0.4% of patients with supraventricular arrhythmias 1
Common Non-Cardiac Side Effects
Neurological Effects
- Dizziness is the most frequent side effect at 18.9%, including lightheadedness, faintness, and near-syncope 1
- Headache occurs in 9.6% of patients 1
- Tremor develops in 4.7% of patients and is a recognized adverse effect requiring consideration of alternative agents 3, 1
- Fatigue affects 7.7% and asthenia 4.9% of patients 1
Visual Disturbances
- Visual problems occur in 15.9% of patients, including blurred vision, difficulty focusing, and spots before eyes 1
- These effects are typically mild, transient, and tolerable 4
Gastrointestinal Effects
Rare but Serious Side Effects
Hepatotoxicity
- Rare reports of hepatic dysfunction including cholestasis and hepatic failure have been documented in postmarketing surveillance 1
- Isolated elevations of serum alkaline phosphatase and transaminases have been reported 1
- Baseline and regular monitoring of liver function tests is recommended, particularly in patients with pre-existing liver disease 5
Hematologic Effects
- Extremely rare reports of blood dyscrasias including leukopenia, granulocytopenia, and thrombocytopenia 1
Pulmonary Effects
- Dyspnea occurs in 10.3% of patients 1
- Rare cases of pneumonitis/pulmonary infiltration possibly due to chronic flecainide treatment 1
Important Clinical Considerations
Dose-Related Effects
- The frequency of serious adverse events increases with higher trough plasma levels, especially when exceeding 1 mcg/mL 1
- Visual disturbances increase from 5.4% at 200 mg/day to 18.0% at 400 mg/day 1
Contraindications and High-Risk Situations
- Absolutely contraindicated in patients with structural heart disease, reduced left ventricular function, or history of myocardial infarction due to increased risk of serious cardiac adverse effects 2, 3
- Should not be used in patients with sinus or AV conduction disease without a pacemaker 2
- Avoid in Brugada syndrome due to risk of idiopathic ventricular fibrillation 2
Drug Interactions
- Flecainide levels are increased by amiodarone, digoxin, ritonavir, saquinavir, and tipranavir 2
- Verapamil requires monitoring of digoxin concentrations when used with flecainide 2
- Drug interactions that increase flecainide levels may potentially increase the risk of all adverse effects including tremor 3
Monitoring Requirements
- Regular ECG monitoring is essential during therapy to detect cardiac conduction abnormalities 3, 5
- Baseline ECG should be obtained prior to initiating therapy 6
- Serum electrolyte levels should be monitored and maintained within normal ranges 6