TAMBOCOR
Clinical safety rating
cautionComprehensive clinical and safety monograph for TAMBOCOR (TAMBOCOR).
Class Ic antiarrhythmic agent; blocks sodium channels, slowing conduction velocity and prolonging refractoriness in cardiac tissues.
| Metabolism | Hepatic metabolism via CYP2D6; active metabolite; renal excretion of unchanged drug and metabolites. |
| Excretion | Renal: 85% (30% unchanged, 55% as inactive metabolites); Fecal: 5%; Biliary: negligible. |
| Half-life | Terminal elimination half-life: 12–27 hours (mean 20 hours); prolonged to 58 hours in heart failure or renal impairment (CrCl < 35 mL/min). |
| Protein binding | 90–95% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 8–10 L/kg; extensive tissue distribution (lung, heart, liver). |
| Bioavailability | Oral: 85–90% (first-pass metabolism minimal). |
| Onset of Action | Oral: 1–2 hours; IV: not available in US (oral only). |
| Duration of Action | 12–24 hours; steady-state achieved in 3–5 days. Dosing interval 12 hours. |
| Molecular Weight | 414.37 |
For atrial fibrillation/flutter: 50 mg orally every 12 hours; may increase by 50 mg every 4 days up to 300 mg/day. For life-threatening ventricular arrhythmias: 100 mg orally every 12 hours; increase by 50 mg every 4 days up to 400 mg/day.
| Dosage form | TABLET |
| Renal impairment | CrCl >50 mL/min: no adjustment; CrCl 35-50 mL/min: 50 mg every 12 hours; CrCl <35 mL/min: 100 mg every 24 hours or 50 mg every 12 hours with caution. |
| Liver impairment | Child-Pugh class A: no adjustment; Child-Pugh class B: reduce dose by 25-50%; Child-Pugh class C: contraindicated or use with extreme caution. |
| Pediatric use | Dosing not established; limited data: 1-3 mg/kg/day orally divided every 8-12 hours; maximum 6 mg/kg/day. |
| Geriatric use | Start at 50 mg every 12 hours; increase slowly with close monitoring of plasma levels and ECG; consider lower doses due to reduced renal function. |
| 1st trimester | Animal studies have shown teratogenic effects; no adequate human studies. Use only if potential benefit justifies risk to fetus. |
| 2nd trimester | May cause fetal arrhythmias; use only if clearly needed. |
| 3rd trimester | May cause fetal arrhythmias; monitor fetal heart rate. Use only if clearly needed. |
Clinical note
Comprehensive clinical and safety monograph for TAMBOCOR (TAMBOCOR).
| Placental transfer | Crosses placenta; cord blood concentrations ~50% of maternal serum. |
| Breastfeeding | Flecainide is excreted into breast milk in small amounts (milk:plasma ratio ~1.0). Monitor infant for bradycardia and arrhythmias. Consider alternative if infant has cardiac disease. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category C. Flecainide crosses the placenta. First trimester: Limited human data; animal studies show fetal toxicity at maternally toxic doses. Second and third trimesters: Risk of fetal arrhythmia, including tachycardia or heart block; may require fetal echocardiography. Avoid in pregnancy unless benefit outweighs risk. |
| Fetal Monitoring | Maternal: ECG monitoring for QRS prolongation, PR interval, and QT interval; plasma flecainide levels (therapeutic range 0.2–1.0 mcg/mL); renal function. Fetal: Fetal heart rate monitoring and echocardiography for signs of arrhythmia or hydrops. |
| Fertility Effects | No specific human data on fertility impairment. Animal studies show no adverse effects on fertility. Theoretical risk of reduced sperm motility due to sodium channel blockade, but not confirmed. |
■ FDA Black Box Warning
May increase mortality in patients with structural heart disease (e.g., post-MI, cardiomyopathy). Reserved for life-threatening arrhythmias.
| Serious Effects |
Pre-existing second- or third-degree AV blockRight bundle branch block with left hemiblock (bifascicular block) unless pacemakerCardiogenic shockKnown hypersensitivity to flecainide
| Precautions | Proarrhythmic effects including new or worsened ventricular arrhythmias, Use caution in patients with conduction abnormalities (e.g., SA node dysfunction, bundle branch block), Heart failure exacerbation due to negative inotropic effects, Electrolyte disturbances (hypokalemia, hypomagnesemia) should be corrected, Plasma monitoring recommended due to narrow therapeutic index |
| Food/Dietary | Grapefruit juice increases flecainide AUC by 15-40% and should be avoided. High-fat meals may delay absorption but do not significantly alter overall exposure. No other specific dietary restrictions. |
| Clinical Pearls | Tambocor (flecainide) is a class Ic antiarrhythmic used for life-threatening ventricular arrhythmias and paroxysmal atrial fibrillation/flutter. It has a narrow therapeutic index and requires ECG monitoring for QRS prolongation (>140 ms) or new arrhythmias. Contraindicated in ischemic heart disease due to increased mortality (CAST trial). Adjust dose in renal impairment (CrCl < 50 mL/min: start at 50 mg q12h). Proarrhythmic risk is highest in patients with structural heart disease or reduced EF. Monitor trough levels (therapeutic range: 0.2-1.0 mcg/mL). |
| Patient Advice | Take exactly as prescribed; do not stop or change dose without consulting your doctor. · Report any new or worsening chest pain, palpitations, fainting, or difficulty breathing immediately. · Avoid grapefruit juice as it can increase flecainide levels and risk of side effects. · Take with or without food; maintain consistent timing to keep levels stable. · Do not crush or chew extended-release capsules; swallow whole. |
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