Tambocor

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.

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 рH 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.