From the Guidelines
Flecainide monitoring should include regular ECG assessments, particularly to detect QRS widening, PR interval prolongation, and QTc prolongation, as well as monitoring of blood levels, renal and hepatic function tests, and electrolyte measurements, especially potassium and magnesium levels, to minimize the risk of toxicity and arrhythmias, as recommended by the most recent guidelines 1.
Key Monitoring Parameters
- ECG assessments to detect:
- QRS widening (>25% from baseline)
- PR interval prolongation
- QTc prolongation
- Blood levels: therapeutic ranges typically between 0.2-1.0 μg/mL
- Renal function tests: important for dosage adjustments in patients with significant renal impairment
- Hepatic function tests: necessary due to approximately 70% of flecainide clearance being through hepatic metabolism
- Electrolyte measurements: particularly potassium and magnesium to prevent imbalances that can potentiate arrhythmias
Clinical Monitoring
- Patients should be monitored for clinical symptoms of toxicity including:
- Visual disturbances
- Dizziness
- Headache
- New or worsening arrhythmias
- More frequent monitoring is recommended when:
From the FDA Drug Label
Flecainide acetate should be used cautiously in patients who are known to have a history of CHF or myocardial dysfunction The initial dosage in such patients should be no more than 100 mg bid (see DOSAGE AND ADMINISTRATION) and patients should be monitored carefully. Close attention must be given to maintenance of cardiac function, including optimization of digitalis, diuretic, or other therapy When feasible, it is recommended that plasma flecainide levels be monitored. Attempts should be made to keep trough plasma levels below 0. 7 to 1 mcg/mL. The pacing threshold in patients with pacemakers should be determined prior to instituting therapy with flecainide acetate, again after one week of administration and at regular intervals thereafter.
The parameters monitored for flecainide include:
- Cardiac function, including optimization of digitalis, diuretic, or other therapy
- Plasma flecainide levels, with attempts to keep trough plasma levels below 0.7 to 1 mcg/mL
- Pacing threshold in patients with pacemakers, prior to instituting therapy, after one week of administration, and at regular intervals thereafter
- PR, QRS, and QT intervals, as flecainide acetate slows cardiac conduction and produces dose-related increases in these intervals 2
From the Research
Parameters Monitored for Flecainide
The following parameters are monitored for flecainide:
- Electrocardiogram (ECG) findings, as flecainide toxicity can cause wide complex tachycardia and other cardiac arrhythmias 3, 4, 5
- Flecainide serum levels, as elevated levels can indicate toxicity 3, 6, 4
- Renal function, as renal impairment can increase the risk of flecainide toxicity 7, 6, 4
- Cardiac function, as flecainide can cause cardiac arrest, dysrhythmias, and heart failure 3, 7, 5
- Potassium levels, as hypokalemia can increase the risk of flecainide toxicity 3
- Sodium levels, as hyponatremia can be a sign of flecainide toxicity 5
Laboratory Tests
Laboratory tests that may be monitored for flecainide include:
- Flecainide level, with a normal range of 0.20-1.00 μg/mL and a toxic range of >1.50 μg/mL 3
- Creatinine level, to assess renal function 6, 4
- Electrolyte levels, including potassium and sodium 3, 5
Special Considerations
Special considerations for monitoring flecainide include:
- Patients with renal dysfunction, as they are at increased risk of flecainide toxicity 7, 6, 4
- Patients with pacemakers, as flecainide toxicity can cause pacemaker ventricular capture latency or failure to capture 4
- Patients taking other medications that may interact with flecainide, as this can increase the risk of toxicity 7