indication

Flecainide is is a class Ic antiarrhythmic agent and as such, it is used for the prevention of paroxysmal supraventricular tachycardias (PSVT), including atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia and other supraventricular tachycardias of unspecified mechanism associated with disablin.

pharmacology

Flecainide has local anesthetic activity and belongs to the membrane stabilizing (Class 1) group of antiarrhythmic agents; it has electrophysiologic effects characteristic of the IC class of antiarrhythmics.

mechanism of action

Flecainide acts on sodium channels on the neuronal cell membrane, limiting the spread of seizure activity and reducing seizure propagation. The antiarrhythmic actions are mediated through effects on sodium channels in Purkinje fibers. Flecainide is a sodium channel blocker, binding to voltage gated sodium channels. It stabilizes the neuronal membrane by inhibiting the ionic fluxes required for the initiation and conduction of impulses. Ventricular excitability is depressed and the stimulation threshold of the ventricle is increased during diastole.

toxicity

Oral LD50 is 50-498 mg/kg in rat. Symptoms of overdose include nausea and vomiting, convulsions, hypotension, bradycardia, syncope, extreme widening of the QRS complex, widening of the QT interval, widening of the PR interval, ventricular tachycardia, AV nodal block, asystole, bundle branch block, cardiac failure, and cardiac arrest.

biotransformation

Hepatic. Flecainide does not undergo any consequential presystemic biotransformation. The two major urinary metabolites are meta-O-dealkylated flecainide (active, but about one-fifth as potent) and the meta-O-dealkylated lactam of flecainide (non-active metabolite).

absorption

Nearly complete following oral administration.

half life

20 hours (range 12-27 hours)

route of elimination

In healthy subjects, about 30% of a single oral dose (range, 10 to 50%) is excreted in urine as unchanged drug. Several minor metabolites (3% of the dose or less) are also found in urine; only 5% of an oral dose is excreted in feces. In patients, free (unconjugated) plasma levels of the two major metabolites are very low (less than 0.05 μg/mL).

drug interactions

Amiodarone: Amiodarone may increase the effect and toxicity of flecainide

Artemether: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Cimetidine: Cimetidine, a moderate CYP2D6 inhibitor, may decrease the metabolism of flecainide.

Cisapride: Increased risk of cardiotoxicity and arrhythmias

Duloxetine: Possible increase in the levels of this agent when used with duloxetine

Lumefantrine: Additive QTc-prolongation may occur. Concomitant therapy should be avoided.

Mesoridazine: Increased risk of cardiotoxicity and arrhythmias

Quinupristin: This combination presents an increased risk of toxicity

Ritonavir: Ritonavir increases the toxicity of the anti-arrhythmic

Tacrolimus: Additive QTc-prolongation may occur increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution.

Terbinafine: Terbinafine may reduce the metabolism and clearance of Flecainide. Consider alternate therapy or monitor for therapeutic/adverse effects of Flecainide if Terbinafine is initiated, discontinued or dose changed.

Terfenadine: Increased risk of cardiotoxicity and arrhythmias

Thioridazine: Increased risk of cardiotoxicity and arrhythmias

Thiothixene: May cause additive QTc-prolonging effects. Increased risk of ventricular arrhythmias. Consider alternate therapy. Thorough risk:benefit assessment is required prior to co-administration.

Tipranavir: Tipranavir, co-administered with Ritonavir, may increase the plasma concentration of Flecainide. Concomitant therapy is contraindicated.

Toremifene: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Consider alternate therapy. A thorough risk:benefit assessment is required prior to co-administration.

Trimipramine: Additive QTc-prolongation may occur, increasing the risk of serious ventricular arrhythmias. Concomitant therapy should be used with caution.

Voriconazole: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Vorinostat: Additive QTc prolongation may occur. Consider alternate therapy or monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).

Ziprasidone: Additive QTc-prolonging effects may increase the risk of severe arrhythmias. Concomitant therapy is contraindicated.

Zuclopenthixol: Additive QTc prolongation may occur. Consider alternate therapy or use caution and monitor for QTc prolongation as this can lead to Torsade de Pointes (TdP).