Flecainide
Flecainide
Generic Name
Flecainide
Mechanism
- Class IC antiarrhythmic agent that inhibits fast inward Na⁺ currents (I_Na) in cardiac myocytes.
- Produces a persistent, reversible blockade of Na⁺ channels during the rapid upstroke phase (phase 0) of the action potential.
- Resulting in:
- Prolonged action‑potential duration (APD) and increased refractory period.
- Slowed conduction velocity across atrial, ventricular, and His‑Purkinje tissue.
- Minimal effect on potassium channels, calcium influx, or autonomic tone.
---
Pharmacokinetics
| Parameter | Detail |
| Absorption | Rapid oral absorption (bioavailability ~ 99 %); peak plasma levels at 0.5–1 h. |
| Distribution | Protein‑bound 70 – 90 % (predominantly albumin). Large volume of distribution (~ 1.8 L/kg). |
| Metabolism | CYP2D6‑mediated N‑dealkylation → flecainide desmethyl metabolite; ~ 35 % orally available unchanged. |
| Elimination | Primarily renal (≈ 63 % unchanged), residual hepatic excretion (~ 20 %). Half‑life 12–15 h (oral). |
| Drug Interactions | CYP2D6 inhibitors (e.g., quinidine, fluoxetine) ↑C_max; stimulators (e.g., carbamazepine) ↓. Concomitant antiarrhythmics (digoxin, amiodarone) ↑sodium channel blockade risk. |
--
•
Indications
- Atrial fibrillation (AF) or atrial flutter in patients without significant structural heart disease (i.e., non‑ischemic cardiomyopathy, no left‑ventricular systolic dysfunction).
- Ventricular tachycardia (VT) – both monomorphic and polymorphic – as an adjunct to catheter ablation or in cases refractory to other drugs.
- Intra‑atrial re‑entry tachycardia; preventive rate‑control in selected patients.
---
Contraindications
| Category | Key Points |
| Contraindications |
• Structural heart disease (e.g., significant LV dysfunction, ischemic heart disease) • Severe ventricular dysfunction (EF < 30 %) • Bundle‑branch block or pre‑existing QRS ≥ 120 ms • Concomitant use with class III antiarrhythmics (amiodarone) |
| Warnings |
• Torsades de pointes risk in prolonged QT and electrolyte disturbances. • Heart failure exacerbation. • Photosensitivity and mild skin rash. • Drug‑drug interactions via CYP2D6 and renal elimination. |
| Precautions |
• Pregnancy category B; avoid in women of childbearing potential unless benefits > risks. • Monitor renal function – dose adjust for CrCl < 50 mL/min. |
--
•
Dosing
- Initial loading (oral)
- *Adults*: 270 mg twice daily (540 mg total) over the first 24 h. Optional single 540 mg load for acute conversion in AF.
- *Pediatrics* (≥ 12 y): Weight‑based, 1 mg/kg twice daily (up‑titrate to ~ 60 mg bid).
- Maintenance
- *Adults*: 100 mg bid or 300 mg qd (target AUC 15–40 ng · h/mL).
- *Pediatric*: 1–2 mg/kg bid.
- Intravenous (rare, in emergencies)
- 1–2 mg/kg IV over 10 min (slow) → 0.4 µg/L target 10‑15 min post‑infusion.
- Follow with oral therapy once hemodynamic stability restored.
Admin notes:
• Take with food to improve absorption.
• Avoid grapefruit juice (CYP2D6 inhibition).
• Initiate with dose ramp-up over 4–6 weeks to minimize proarrhythmia.
---
Adverse Effects
| Adverse Effect | Frequency / Severity |
| Common |
• Nausea/vomiting (≈ 15 %) • Drowsiness / mild CNS depression (≈ 10 %) • Vision changes (blurring, halos) (≈ 5 %) |
| Serious |
• QT prolongation leading to torsades de pointes (rare, < 1 %) • Ventricular arrhythmias (especially in EF < 30 %) • Exacerbation of heart failure (≈ 3 %) • Skin rash/erythema multiforme in ~ 1 % |
--
•
Monitoring
| Parameter | Frequency |
| Baseline |
• ECG (QRS width, QTc, presence of bundle‑branch block) • Serum electrolytes (K⁺, Mg²⁺) • Renal function (CrCl), hepatic panel • Cardiac imaging (EF) if indicated |
| During Therapy |
• ECG at 24 h, 1 wk, and at every dose increment (QRS ≤ 130 ms, QTc < 450 ms) • Blood flecainide level (if adverse effect or dose adjustment) • Renal & hepatic labs monthly in chronic use • Monitor for drug‑drug interactions |
| Post‑Procedure |
• Continuous telemetry for 24 h after IV bolus or ablation • Follow‑up arrhythmia recurrence assessment |
--
•
Clinical Pearls
- "QRS ≤ 120 ms is the golden rule" – a narrow QRS on baseline ECG predicts favorable conduction properties and reduces the risk of proarrhythmia.
- Flecainide + β‑blocker: Combining with short‑acting β‑blockers (e.g., metoprolol) can mitigate atrial‑to‑ventricular conduction delays and lower syncope risk during initial titration.
- Sodium‑channel blockade in ischemia: Avoid flecainide in patients with recent MI or known coronary artery disease; even a brief ischemic insult can provoke malignant arrhythmias.
- Renal dose adjustment: In chronic kidney disease (CrCl 30–50 mL/min) reduce maintenance dose to 200 mg bid; if CrCl 120 ms.
- Drug holidays: For patients presenting with atrial flutter conversion and early recurrence, a short (48‑72 h) drug holiday can help assess intrinsic AF tendency versus refractory arrhythmia.
--
• *This drug card is intended for educational purposes. Always corroborate with current prescribing information and institutional protocols before clinical use.*