Flecainide Toxicity - Symptoms, Diagnosis, and Treatment

Introduction

Flecainide is a class of antiarrhythmic agents used to prevent and treat heart rhythm disorders. An overdose of flecainide can cause heart failure, dysrhythmias, and cardiac arrest. Yet, despite these severe side effects of flecainide, clinicians are unaware of the toxicities. Flecainide intoxication is rare but serious due to the potential for cardiogenic (heart) shock. Flecainide toxicity diagnosis can be difficult and usually misdiagnosed. The clinicians are unfamiliar with the signs and symptoms of Flecainide toxicity as the Flecainide serum level may take days to result. The clinicians should be aware as the usage of Flecainide is growing and count it as a differential diagnosis in patients who are on Flecainide. Treatment can be lifesaving if initiated promptly after proper diagnosis.

What Is Flecainide?

Flecainide is a subclass of antiarrhythmic drugs. Anti-arrhythmic drugs are used to prevent and treat irregularities of cardiac rhythm. Cardiac arrhythmias arise due to abnormal impulse generation or abnormal impulse conduction or both. Impulse generation refers to the signal that arises from the heart, which is sent to the brain. Arrhythmias are caused by altering the electrophysiological (electric activity of the heart) properties of the heart’s fibers. In addition, the imbalance of electrolytes and pH, stretching, injury, drug, and anti-arrhythmic drugs can cause arrhythmia.

Anti-arrhythmic drugs are classified into four class system, which considers the drug's primary action:

• Class 1- The primary action of the drug in this class is to limit the conductance of sodium and potassium across the cell membrane and act as a local anesthetic (a substance that induces insensitivity to pain)action.

  • Subclass 1(A) - Quinidine, Procainamide.

  • Subclass 1(B) - Lidocaine, Mexiletine.

  • Subclass 1(C) - Flecainide.

• Class 2 - The primary action of class 2 drugs is to suppress adrenergically mediated ectopic activity and delay after-depolarization. Example - Propranolol.

• Class 3 - The characteristic action of class 3 anti-arrhythmic is the prolongation of repolarization. Example - Dofetilide

• Class 4 - The Class 4 drug are calcium channel blockers. Example - Verapamil, Diltiazem.

Flecainide is a subclass of class 1(C) drugs. Flecainide is the most potent sodium channel blocker. Flecainide delay conduction in the heart in patients with arrhythmias.

What Are the Side-Effects of Flecainide?

The following are the side effects of Flecainide:

• Dizziness.

• Visual disturbances.

• Headache.

• Nausea.

• Dyspnea (shortness of breath).

• Chest pain.

• Cardiac arrest (when the heart suddenly stops beating, resulting in death).

• Arrhythmias (a condition characterized by abnormal heart rhythm).

• Heart failure (a condition that affects the pumping of the heart).

• Acute kidney failure.

• Hypokalemia (low level of potassium).

• Hypotension (low blood pressure).

• Seizures (sudden disturbances in the brain) in worst cases of Flecainide overdose.

What Is Flecainide Toxicity?

Antiarrhythmic drugs have the potential to cause or trigger arrhythmias instead of suppressing them. This proarrhythmic activity occurs in 4 percent to 12 percent of patients on flecainide therapy. These activities with a similar percentage are noted with other antiarrhythmic agents. The overdose of Flecainide in the cardiac patient during the treatment of arrhythmia causes Flecainide toxicity. The most dangerous adverse effect is ventricular tachycardia. Several studies suggest a daily maintenance dose of 200 mg or less.

The following are the side effects of Flecainide toxicity:

• Ventricular Tachycardia - Ventricular tachyarrhythmias are Flecainide toxicity's most serious side effects. Ventricular tachyarrhythmias refer to the irregular signal from the ventricle (lower chamber of the heart). These rhythms can degenerate into ventricular fibrillation (fibrosis of the lower chamber of the heart) and lead to sudden cardiac death.

• Severe Bradycardia - Bradycardia refers to a decreased heartbeat.

What Are the Symptoms of Flecainide Toxicity?

Flunacide toxicity is a serious condition. The toxic effects of Flunacide can cause damage to the liver, kidneys, and gastrointestinal tract, and can even be fatal in some cases.

The following are the symptoms of flecainide toxicity:

• Loss of appetite.

• Vomiting and diarrhea.

• Lethargy and weakness.

• Difficulty urinating.

• Yellowing of the skin and mucous membranes (jaundice).

• Seizures or convulsions.

How to Diagnose Flecainide Toxicity?

Flecainide toxicity is rare but usually misdiagnosed. The diagnosis of Flecainide toxicity is difficult as Flecainide serum level may take days to result. The dysrhythmia impact linked with Flecainide use is one of the most problematic side effects. Hence it is typically diagnosed best by electrocardiogram (ECG).

The following ways to diagnose Flecainide toxicity:

• Blood Tests - A complete blood test will show a high level of Flecainide in the blood. Patients with Flecainide toxicities are detected with hypokalemia. Blood tests can examine the low level of potassium in the blood.

• Electrocardiogram (ECG) - Easy is a technique to measure the heart's electric impulses. Patients with Flecainide toxicities show abnormal electric activities obtained from the heart.

• Liver Function Tests (LFT) - LFT is done to detect abnormalities in the level of enzymes of the liver. Patients with Flecainide toxicities have abnormal LFTs.

How to Treat Flecainide Toxicity?

Fatalities usually occur due to rapid-onset hypotension and ventricular dysrhythmias after severe overdoses. Therefore, early recognition and proper treatment are vital. The treatment of Flecainide toxicity involves cessation of Flecainide medication as soon as possible.

The following ways can treat Flecainide toxicity:

• Flecainide therapy should be discontinued as the signs of intoxication is observed.

• Increasing the excretion of Flecainide.

• The patient should be intubated and ventilated mechanically.

• Cardiogenic shock can be treated with Dopamine and a sodium load infusion.

• Physostigmine salicylate can be given to protect against many cardiotoxic agents.

• Norepinephrine infusion for blood pressure support to treat hypotension.

• The ventricular tachycardia resolved once the Flecainide was discontinued.

• Acute kidney failure (AKI) resolved after stabilization of hemodynamic (circulatory support).

• The toxic amounts of flecainide were removed with gastric lavage (emptying of gastroesophageal passage).

Conclusion

Flecainide intoxication is rare but serious due to the potential for cardiogenic shock. The potential to cause heart failure is a serious complication that highlights the importance of maintaining doctors' differential diagnosis for the patient taking Flecainide. Flecainide intoxication is caused due to overdose of Flecainide. The recommended dose of Flecainide is 200 mg or less. With proper investigation, such as ECG and laboratory investigation, can point out Flecainide intoxication. Early recognition and proper treatment can be life-saving if initiated promptly.