FLECAINIDE ACETATE
Clinical safety rating
safeAnimal studies have demonstrated safety
Animal studies have demonstrated safety
Paroxysmal atrial fibrillation/flutter (including atrial fibrillation associated with Wolff-Parkinson-White syndrome)Paroxysmal supraventricular tachycardias (including atrioventricular nodal reentrant tachycardia and atrioventricular reentrant tachycardia)Sustained ventricular tachycardia (life-threatening)
atrial fibrillation
Class Ic antiarrhythmic agent; sodium channel blocker with slow kinetics of dissociation, slowing conduction velocity with minimal effect on repolarization.
| Metabolism | Primarily hepatic via CYP2D6; active metabolite meta-O-dealkylated flecainide; renal excretion of unchanged drug and metabolites. |
| Excretion | Renal: approximately 85% (10-50% unchanged, the rest as meta-O-dealkylated metabolites); fecal/biliary: minor (<5%). |
| Half-life | Terminal half-life 12-27 hours (mean 20 hours) in patients with normal renal function; may increase to 20-40 hours in renal impairment (CrCl <35 mL/min). |
| Protein binding | Approximately 40-50% bound to plasma proteins (mainly albumin and alpha-1-acid glycoprotein). |
| Volume of Distribution | Apparent Vd 5-13 L/kg (mean 9 L/kg), indicating extensive tissue distribution. |
| Bioavailability | Oral: 90-95% (high, with minimal first-pass metabolism). |
| Onset of Action | Oral: 1-2 hours; intravenous: within minutes. |
| Duration of Action | Oral: 12-24 hours (dosing every 12 hours); intravenous: 4-6 hours. |
| Molecular Weight | 414.34 |
Initial: 100 mg every 12 hours; increase by 50 mg twice daily every 4 days; maximum 400 mg/day. Oral route.
| Dosage form | TABLET |
| Renal impairment | CrCl >50 mL/min: no adjustment; CrCl 35-50 mL/min: decrease dose by 25%; CrCl <35 mL/min: not recommended or use with extreme caution, dose at 50% reduction with careful monitoring. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: reduce dose by 25-50%; Child-Pugh Class C: avoid use or reduce dose by 50% with close monitoring. |
| Pediatric use | For supraventricular tachycardia: 1-3 mg/kg/day orally divided every 8-12 hours; maximum 8 mg/kg/day; for ventricular arrhythmias: 2-6 mg/kg/day orally divided every 8-12 hours; maximum 8 mg/kg/day. |
| Geriatric use | Start at 50-100 mg every 12 hours; increase cautiously due to reduced renal function and increased risk of proarrhythmia; monitor renal function and ECG. |
| 1st trimester | Flecainide crosses the placenta. Limited data; risk of fetal arrhythmias. Use only if clearly needed. |
| 2nd trimester | Monitor fetal heart rate. May cause fetal bradycardia. Use if benefit outweighs risk. |
| 3rd trimester | Similar risk; avoid near term due to potential neonatal effects. Use with caution. |
Clinical note
Other drugs that prolong the QT interval increase risk of proarrhythmia Can cause new or worsened arrhythmias.
| Placental transfer | Crosses placenta; fetal concentrations approximately 50-70% of maternal levels. |
| Breastfeeding | Flecainide is excreted in breast milk in low concentrations. Monitor infant for bradycardia and arrhythmias. Consider alternative if infant has cardiac issues. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Flecainide crosses the placenta. First trimester: Limited human data; animal studies show no major teratogenicity but embryo-fetal toxicity at high doses. Second and third trimesters: Use only if maternal benefit outweighs fetal arrhythmia risk; may cause fetal bradycardia. Fetal/neonatal adverse effects include proarrhythmia, negative inotropy. |
| Fetal Monitoring | Monitor maternal ECG, heart rate, blood pressure, and serum flecainide levels (especially renal impairment). Fetal monitoring: serial fetal echocardiography for fetal arrhythmia, growth, and well-being. Neonatal monitoring: ECG, heart rate, and serum drug levels after birth. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies show no impairment of fertility at clinically relevant doses. |
■ FDA Black Box Warning
None (however, Class Ic drugs are contraindicated in patients with structural heart disease due to increased mortality in CAST trial).
| Common Effects | atrial fibrillation |
| Serious Effects |
Cardiogenic shockPreexisting second- or third-degree AV block (unless pacemaker present)Right bundle branch block with left hemiblock (bifascicular block) without pacemakerKnown hypersensitivity to flecainideStructural heart disease (e.g., coronary artery disease, prior MI) – increase in mortality noted in CAST trial
| Precautions | Proarrhythmic effects (worsening arrhythmias or new arrhythmias), Use with structural heart disease (especially post-MI) increases risk of cardiac arrest, Heart failure or left ventricular dysfunction, Electrolyte disturbances (hypokalemia, hypomagnesemia), Renal impairment (dose reduction needed), Hepatic impairment, Conduction disturbances (pre-existing sinus node dysfunction, second- or third-degree AV block), Pacemaker-dependent patients (increase pacing threshold), Ocular effects (corneal deposits, visual disturbances) |
| Food/Dietary | Grapefruit juice increases flecainide plasma concentration by inhibiting CYP2D6; avoid concurrent intake. No other significant food interactions. |
| Clinical Pearls | Flecainide is a class IC antiarrhythmic with potent sodium channel blockade; contraindicated in structural heart disease (e.g., post-MI, LVH, CAD) due to increased mortality (CAST trial). Monitor QRS and QTc intervals; dose reduce in renal impairment (CrCl <35 mL/min). Avoid in atrial fibrillation with flutter due to risk of 1:1 conduction. Efficacy in catecholaminergic polymorphic ventricular tachycardia (CPVT) and paroxysmal atrial fibrillation. Therapeutic plasma level 0.2-1.0 mcg/mL. |
| Patient Advice | Take exactly as prescribed; do not skip doses or double up. · Report any new or worsening palpitations, chest pain, shortness of breath, or fainting. · Avoid grapefruit juice as it may increase drug levels. · Monitor for visual disturbances (blurred vision, double vision) and gastrointestinal upset. · Do not stop abruptly; taper under medical supervision to avoid arrhythmia recurrence. |
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