TAMBOCOR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TAMBOCOR (TAMBOCOR).

How it works

Class Ic antiarrhythmic agent; blocks sodium channels, slowing conduction velocity and prolonging refractoriness in cardiac tissues.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TAMBOCOR (TAMBOCOR).

Breastfeeding	Flecainide is excreted into breast milk. Milk-to-plasma ratio approximately 2.5 (range 1.4–3.8). Infant exposure estimated at 3–5% of maternal weight-adjusted dose. Monitor infant for bradycardia, arrhythmia, and feeding difficulties. Use with caution; alternative agents preferred.
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.

Warnings & precautions

■ FDA Black Box Warning

May increase mortality in patients with structural heart disease (e.g., post-MI, cardiomyopathy). Reserved for life-threatening arrhythmias.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Second- or third-degree AV block (unless pacemaker in place)","Bifascicular block or distal conduction blocks","Cardiogenic shock or severe hypotension","Pre-existing prolonged QT interval","History of ventricular arrhythmias associated with structural heart disease"]

Clinical Precautions

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"]

Clinical Tips & Counseling

Drug interactions

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TAMBOCOR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for TAMBOCOR (TAMBOCOR).

How it works

Class Ic antiarrhythmic agent; blocks sodium channels, slowing conduction velocity and prolonging refractoriness in cardiac tissues.

What the body does with it

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.

Classification & Brands

Dosing & administration

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.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for TAMBOCOR (TAMBOCOR).

Breastfeeding	Flecainide is excreted into breast milk. Milk-to-plasma ratio approximately 2.5 (range 1.4–3.8). Infant exposure estimated at 3–5% of maternal weight-adjusted dose. Monitor infant for bradycardia, arrhythmia, and feeding difficulties. Use with caution; alternative agents preferred.
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.

Warnings & precautions

■ FDA Black Box Warning

May increase mortality in patients with structural heart disease (e.g., post-MI, cardiomyopathy). Reserved for life-threatening arrhythmias.