Tambocor Side Effects Center

Last updated on RxList: 3/25/2021
Tambocor Side Effects Center

What Is Tambocor?

Tambocor is an antiarrhythmic prescribed in certain situations to prevent serious heart rhythm disorders including irregular heartbeat (such as persistent ventricular tachycardia and paroxysmal supraventricular tachycardia). Tambocor is also used to prevent certain types of irregular heartbeat from returning (such as atrial fibrillation). Tambocor is available in generic form.

What Are Side Effects of Tambocor?

Common side effects of Tambocor include:

  • dizziness,
  • vision problems (such as blurred vision, problems focusing, seeing spots),
  • shortness of breath,
  • headache,
  • nausea,
  • vomiting,
  • stomach pain,
  • diarrhea,
  • constipation,
  • tremor or shaking,
  • tiredness,
  • weakness,
  • anxiety,
  • depression,
  • numbness or
  • tingling.

Tell your doctor if you have unlikely but serious side effects of Tambocor including new or worsening symptoms of heart failure (such as ankle/leg swelling, increased tiredness, or increased shortness of breath when lying down).

Dosage for Tambocor

The first few doses of Tambocor are administered in a hospital setting in case the medication causes serious side effects. Tell your doctor all medications you are taking.

What Drugs, Substances, or Supplements Interact with Tambocor?

Tambocor may have adverse interactions with many other medications. Interactions may occur with cimetidine, digoxin, diuretics, seizure medications, beta blockers, other heart rhythm medications, and other drugs.

Tambocor During Pregnancy and Breastfeeding

During pregnancy, this medication should be used only when needed. Discuss the risks and benefits with your doctor. This medication passes into breast milk. However, this drug is considered unlikely to harm a nursing infant. Consult your doctor before breastfeeding.

Additional Information

Our Tambocor Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


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Tambocor Consumer Information

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Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • fast or pounding heartbeats;
  • fluttering in your chest, shortness of breath, and sudden dizziness (like you might pass out);
  • slow heart rate, weak pulse, slow breathing (breathing may stop);
  • feeling short of breath;
  • swelling, rapid weight gain;
  • pale skin, easy bruising or bleeding, unusual weakness;
  • fever, flu-like symptoms; or
  • jaundice (yellowing of the skin or eyes).

Common side effects may include:

  • dizziness;
  • vision problems;
  • trouble breathing;
  • headache;
  • nausea; or
  • feeling weak or tired.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


Heart Disease: Symptoms, Signs, and Causes See Slideshow
Tambocor Professional Information


In post-myocardial infarction patients with asymptomatic PVCs and non-sustained ventricular tachycardia, TAMBOCOR (flecainide) therapy was found to be associated with a 5.1% rate of death and non-fatal cardiac arrest, compared with a 2.3% rate in a matched placebo group. (See WARNINGS.)

Adverse effects reported for TAMBOCOR (flecainide) , described in detail in the Warnings section, were new or worsened arrhythmias which occurred in 1% of 108 patients with PSVT and in 7% of 117 patients with PAF; and new or exacerbated ventricular arrhythmias which occurred in 7% of 1330 patients with PVCs, non-sustained or sustained VT. In patients treated with flecainide for sustained VT, 80% (51/64) of proarrhythmic events occurred within 14 days of the onset of therapy. 198 patients with sustained VT experienced a 13% incidence of new or exacerbated ventricular arrhythmias when dosage was initiated at 200 mg/day with slow upward titration, and did not exceed 300 mg/day in most patients. In some patients, TAMBOCOR (flecainide) treatment has been associated with episodes of unresuscitatable VT or ventricular fibrillation (cardiac arrest). (See WARNINGS.) New or worsened CHF occurred in 6.3% of 1046 patients with PVCs, non-sustained or sustained VT. Of 297 patients with sustained VT, 9.1% experienced new or worsened CHF. New or worsened CHF was reported in 0.4% of 225 patients with supraventricular arrhythmias. There have also been instances of second- (0.5%) or third-degree (0.4%) AV block. Patients have developed sinus bradycardia, sinus pause, or sinus arrest, about 1.2% altogether (see WARNINGS). The frequency of most of these serious adverse events probably increases with higher trough plasma levels, especially when these trough levels exceed 1.0μg/mL.

There have been rare reports of isolated elevations of serum alkaline phosphatase and isolated elevations of serum transaminase levels. These elevations have been asymptomatic and no cause and effect relationship with TAMBOCOR (flecainide) has been established. In foreign postmarketing surveillance studies, there have been rare reports of hepatic dysfunction including reports of cholestasis and hepatic failure, and extremely rare reports of blood dyscrasias. Although no cause and effect relationship has been established, it is advisable to discontinue TAMBOCOR (flecainide) in patients who develop unexplained jaundice or signs of hepatic dysfunction or blood dyscrasias in order to eliminate TAMBOCOR (flecainide) as the possible causative agent.

Incidence figures for other adverse effects in patients with ventricular arrhythmias are based on a multicenter efficacy study, utilizing starting doses of 200 mg/day with gradual upward titration to 400 mg/day. Patients were treated for an average of 4.7 months, with some receiving up to 22 months of therapy. In this trial, 5.4% of patients discontinued due to non-cardiac adverse effects.

Table 1 Most Common Non-Cardiac Adverse Effects in Ventricular Arrhythmia Patients Treated with TAMBOCOR (flecainide) in the Multicenter Study

Adverse Effect Incidence
All 429 Patients at Any Dose
Incidence by Dose During Upward Titration
Dizziness* 18.9% 11.0% 10.6% 13.0%
Visual Disturbances† 15.9% 5.4% 12.3% 18.0%
Dyspnea 10.3% 5.2% 7.5% 4.0%
Headache 9.6% 4.5% 6.1% 9.0%
Nausea 8.9% 4.9% 4.8% 6.0%
Fatigue 7.7% 4.5% 4.4% 3.0%
Palpitation 6.1% 3.5% 2.4% 7.0%
Chest Pain 5.4% 3.1% 3.8% 1.0%
Asthenia 4.9% 2.6% 2.0% 4.0%
Tremor 4.7% 2.4% 3.4% 2.0%
Constipation 4.4% 2.8% 2.1% 1.0%
Edema 3.5% 1.9% 1.4% 2.0%
Abdominal Pain 3.3% 1.9% 2.4% 1.0%
* Dizziness includes reports of dizziness, lightheadedness, faintness, unsteadiness, near syncope, etc.
†Visual disturbance includes reports of blurred vision, difficulty in focusing, spots before eyes, etc.

The following additional adverse experiences, possibly related to TAMBOCOR (flecainide) therapy and occurring in 1% to less than 3% of patients, have been reported in acute and chronic studies: Body as a Whole– malaise, fever; Cardiovascular– tachycardia, sinus pause or arrest; Gastrointestinal– vomiting, diarrhea, dyspepsia, anorexia; Skin– rash; Visual– diplopia; Nervous System– hypoesthesia, paresthesia, paresis, ataxia, flushing, increased sweating, vertigo, syncope, somnolence, tinnitus; Psychiatric– anxiety, insomnia, depression.

The following additional adverse experiences, possibly related to TAMBOCOR (flecainide) , have been reported in less than 1% of patients: Body as a Whole– swollen lips, tongue and mouth; arthralgia, bronchospasm, myalgia; Cardiovascular– angina pectoris, seconddegree and third-degree AV block, bradycardia, hypertension, hypotension; Gastrointestinal– flatulence; Urinary System– polyuria, urinary retention; Hematologic– leukopenia, granulocytopenia, thrombocytopenia; Skin– urticaria, exfoliative dermatitis, pruritis, alopecia; Visual– eye pain or irritation, photophobia, nystagmus; Nervous System– twitching, weakness, change in taste, dry mouth, convulsions, impotence, speech disorder, stupor, neuropathy; Respiratory– pneumonitis/pulmonary infiltration possibly due to chronic flecainide treatment; Psychiatric– amnesia, confusion, decreased libido, depersonalization, euphoria, morbid dreams, apathy. For patients with supraventricular arrhythmias, the most commonly reported noncardiac adverse experiences remain consistent with those known for patients treated with TAMBOCOR (flecainide) for ventricular arrhythmias. Dizziness is possibly more frequent in PAF patients.

Read the entire FDA prescribing information for Tambocor (Flecainide)


In the U.S., 1 in every 4 deaths is caused by heart disease. See Answer

© Tambocor Patient Information is supplied by Cerner Multum, Inc. and Tambocor Consumer information is supplied by First Databank, Inc., used under license and subject to their respective copyrights.

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