Tambocor

Tam·bo·cor (tmb-kôr)

A trademark for the drug flecainide acetate.

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flecainide acetate Warning - Hazardous drug!

Tambocor

Pharmacologic class: Cardiac benzamide local anesthetic

Therapeutic class: Antiarrhythmic (class IC)

Pregnancy risk category C

FDA Boxed Warning

• In patients with non-life-threatening ventricular arrhythmias who had recent myocardial infarctions and were receiving drug, excessive deaths and nonfatal cardiac arrest rates occurred. Don't give to patients without life-threatening ventricular arrhythmias.
• Drug isn't recommended for patients with chronic atrial fibrillation.
• Patients who received drug for atrial flutter have experienced 1:1 atrioventricular conduction. Paradoxical increase in ventricular rate also may occur in patients with atrial fibrillation who receive drug.

Action

Inhibits fast sodium channels of myocardial cell membrane. Also slows conduction, shortens action potential, stops paroxysmal reentrant supraventricular tachycardia, and decreases conduction in accessory pathways in Wolff-Parkinson-White syndrome.

Availability

Tablets: 50 mg, 100 mg, 150 mg

⊘Indications and dosages

➣ Supraventricular tachyarrhythmias (including paroxysmal supraventricular tachycardia and paroxysmal atrial fibrillation or flutter)

Adults: Initially, 50 mg P.O. q 12 hours, increased by 50 mg b.i.d. q 4 days until desired response occurs or maximum daily dosage of 300 mg is reached.

➣ Sustained, life-threatening ventricular tachycardia

Adults: Initially, 100 mg P.O. q 12 hours, increased by 50 mg b.i.d. q 4 days until desired response occurs or maximum daily dosage of 400 mg is reached.

Dosage adjustment

• Heart failure
• Renal impairment

Off-label uses

• Ventricular arrhythmias
• Wolff-Parkinson-White syndrome

Contraindications

• Hypersensitivity to drug
• Preexisting atrioventricular block or right bundle-branch block
• Recent MI
• Cardiogenic shock

Precautions

Use cautiously in:
• heart failure, renal impairment
• patients taking concurrent amiodarone, beta-adrenergic blockers, disopyramide, or verapamil
• pregnant or breastfeeding patients
• children (safety not established).

Administration

• Initiate therapy only in hospital setting with trained personnel and continuous ECG monitoring.
• Before giving, correct hypokalemia or hyperkalemia.
• Be aware that dosage may be reduced once arrhythmias have been adequately controlled.

Route	Onset	Peak	Duration
P.O.	Unknown	2-3 hr	12 hr

Adverse reactions

CNS: dizziness, anxiety, fatigue, headache, depression, malaise, tremor, weakness, hypoesthesia, paresthesia

CV: chest pain, palpitations, second- or third-degree heart block, heart failure, new or worsening arrhythmias

EENT: blurred vision, visual disturbances, corneal deposits

GI: nausea, vomiting, constipation, abdominal pain, dyspepsia, anorexia

Hepatic: hepatitis

Respiratory: dyspnea

Skin: rash, diaphoresis

Other: edema, fever

Interactions

Drug-drug. Acidifying drugs: increased renal elimination, decreased efficacy of flecainide (with urine pH below 5)

Alkalizing drugs: increased flecainide blood level, possible toxicity

Amiodarone: doubling of flecainide blood level

Beta-adrenergic blockers: increased blood levels of both drugs

Beta-adrenergic blockers, disopyramide, verapamil: additive myocardial depressant effect

Digoxin: 15% to 25% increase in digoxin blood level

Other antiarrhythmics (including calcium channel blockers): increased risk of arrhythmias

Drug-diagnostic tests. Alkaline phosphatase: increased level (with prolonged therapy)

Drug-food. Foods that decrease urine pH below 5 (such as acidic juices): increased renal elimination and possibly decreased efficacy of drug

Foods that increase urine pH above 7 (as in strict vegetarian diets): increased drug blood level

Drug-behaviors. Smoking: increased plasma clearance and decreased efficacy of drug

Patient monitoring

☞ Monitor ECG for worsening arrhythmias.
• Measure pacing threshold 1 week before therapy starts and again after 1 week of therapy.
• Monitor potassium and flecainide blood levels.
• Assess respiratory status regularly.
• Monitor hepatic function tests.

Patient teaching

☞ Instruct patient to immediately report cardiac or respiratory symptoms, unusual tiredness, or yellowing of skin or eyes.
• Tell patient drug may cause numbness. Advise him to avoid injury to areas with sensory impairment.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, alertness, and vision.
• Advise patient to minimize GI upset by eating small, frequent servings of food and drinking adequate fluids.
• Tell female patient to inform prescriber if she is pregnant or breastfeeding.
• Inform patient that he'll undergo regular blood testing during therapy.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, foods, and behaviors mentioned above.