Tambocor Side Effects

Generic name: flecainide

Note: This document contains side effect information about flecainide. Some of the dosage forms listed on this page may not apply to the brand name Tambocor.

Some side effects of Tambocor may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to flecainide: oral tablet

Get emergency medical help if you have any of these signs of an allergic reaction while taking flecainide (the active ingredient contained in Tambocor) hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have a serious side effect such as:

• slow heart rate, weak pulse, fainting, slow breathing (breathing may stop);

• dizziness, fainting, fast or pounding heartbeat;

• feeling short of breath, even with mild exertion;

• swelling, rapid weight gain;

• low potassium (confusion, uneven heart rate, extreme thirst, increased urination, leg discomfort, muscle weakness or limp feeling);

• high potassium (slow heart rate, weak pulse, muscle weakness, tingly feeling);

• pale skin, easy bruising or bleeding, unusual weakness; or

• jaundice (yellowing of the skin or eyes).

Less serious side effects of flecainide may include:

• dizziness;

• tremor or shaking;

• headache;

• anxiety or depression;

• vision problems;

• nausea, vomiting, stomach pain;

• diarrhea, constipation; or

• numbness or tingling.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

For Healthcare Professionals

Applies to flecainide: oral tablet

General

The Cardiac Arrhythmia Suppression Trial (CAST) revealed significantly higher mortality associated with flecainide (the active ingredient contained in Tambocor) in patients with a recent history (more than six days but less than two years prior to study) of myocardial infarction (MI) and non-life-threatening ventricular ectopy relative to placebo (5.1% versus 2.3%). The risk of death relative to placebo in patients with a recent history of Q-wave MI and non-Q-wave MI is 8.7 and 1.7, respectively. Use of flecainide in this context is potentially harmful.

Side effects are more likely when plasma flecainide concentrations are greater than 1.0 mcg/mL.

Cardiovascular

Risk factors for a proarrhythmic effect include underlying congenital or structural heart disease.

A case of "pseudoinfarction" has been reported in which flecainide (the active ingredient contained in Tambocor) induced a transient right bundle branch block with a focal block in the septal fibers of the left bundle branch system. An electrocardiogram (ECG) also revealed ST segment elevations and a Q-wave pattern, consistent with septal infarction. The patient did not have a myocardial infarction by enzyme studies, and the ECG abnormalities resolved after discontinuation of flecainide.

One patient with a history of ischemic congestive heart failure, myocardial infarction (MI), and ventricular arrhythmias developed profound cardiogenic shock without evidence of MI or a new or worsened ventricular arrhythmia. The associated serum flecainide concentration was 1.8 mcg/mL.

Cardiovascular side effects including arrhythmias are the most serious side effects. Flecainide may cause or exacerbate arrhythmias in 1% of patients with preexisting paroxysmal supraventricular tachycardia and in 7% of patients with paroxysmal atrial fibrillation. Flecainide may also exacerbate arrhythmias in 7% to 13% of patients with preexisting sustained or nonsustained ventricular arrhythmias.

Flecainide-induced arrhythmias include sinus bradycardia or arrest in 2%, bundle branch blocks in 1%, increased premature ventricular depolarizations in 1%, ventricular tachycardia or fibrillation in 0.5%, and sudden death in 0.2% of patients. New ventricular arrhythmias have been reported in 3.4% of patients.

Flecainide may cause prolongation of the PR, QRS, and corrected QT intervals. Most of the QT interval prolongation is attributable to widening of the QRS complex rather than prolongation of the JT interval. Rare cases of torsades de pointes have been reported.

Exacerbation of congestive heart failure is rare and only occurs in about 0.5% and 9% of patients with preexisting supraventricular arrhythmias and ventricular arrhythmias, respectively. Hypotension is almost exclusively associated with intravenous administration of flecainide.

Nervous system

Nervous system side effects, such as dizziness and visual disturbances (including blurred vision, decreased acuity, and scotomata) occur in 13% to 28% of patients who are taking flecainide (the active ingredient contained in Tambocor) doses of 400 mg per day. Transient headaches, asthenia, feelings of a thick tongue or lips, fatigue, paresthesias, and tremors have been reported in 2% to 10% of patients.

Flecainide may exacerbate myasthenia gravis.

At least 6 cases of flecainide-induced peripheral neuropathy (sensory loss) have been reported and it appears to develop after prolonged use ( 2 to 10 years). Following discontinuation of flecainide therapy, symptoms (e.g., lower-extremity weakness and/or paresthesias, gait disturbance) resolved over 3 to 6 months. However, in some cases the neuropathy did not resolve after discontinuation of flecainide.

Gastrointestinal

Gastrointestinal side effects include abdominal pain, nausea, and constipation in 1% to 4% of patients. Diarrhea occurs rarely.

Musculoskeletal

Musculoskeletal side effects including weakness has been reported and may be more likely in patients with underlying muscular disorders.

A 33-year-old woman with atrial fibrillation, mitral valve prolapse, and a congenital muscle fiber disproportion myopathy developed muscle weakness which partially resolved after flecainide dosage reduction and completely resolved after substitution of flecainide with other antiarrhythmic agents.

Ocular

High performance liquid chromatographic analysis of excised corneal deposits in one patient revealed opacities with the same chromatographic characteristics of flecainide (the active ingredient contained in Tambocor)

Ocular side effects are limited to rare cases of corneal deposits.

Genitourinary

Class I antiarrhythmic agents such as flecainide (the active ingredient contained in Tambocor) have local anesthetic and anticholinergic properties which may rarely cause urinary retention.

Genitourinary side effects including complaints of impotence are reported in 4% of patients. A case of urinary retention associated with flecainide has been reported.

Respiratory

A case of reversible flecainide-induced pneumonitis was reported in a 61-year-old man with a remote history of pulmonary tuberculosis. A complete infectious disease work-up was negative. Serial bronchial-alveolar lavages and chest radiographs were consistent with a drug-induced process.

Respiratory side effects are extremely rare.

Hematologic

One patient developed leukopenia after 5 months of flecainide (the active ingredient contained in Tambocor) therapy. The leukopenia resolved after drug discontinuation and did not recur when flecainide was reinstituted. The leukopenia may have been due to a concurrent viral infection.

Hematologic side effects are extremely rare.

Hepatic

Hepatic side effects including enzyme concentration elevations have been reported in rare cases.

Psychiatric

Psychiatric side effects including paranoid psychosis was reported in a 62-year-old patient receiving flecainide (the active ingredient contained in Tambocor) for the treatment of malignant neuropathic pain.

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