CADENCE 100

Indications

• Atrial fibrillation
• Atrial flutter
• Ventricular tachycardia
• Paroxysmal supraventricular tachycardia

Dosage

Children: Refer to the BNF for Children for specific dosing information tailored to paediatric patients.

Adults: The usual initial oral dose is 50 mg every 12 hours, which may be increased to 100 mg every 12 hours based on clinical response and tolerability.

Mechanism of action

Flecainide blocks fast inward sodium channels and slowly unbinds during diastole, prolonging the refractory period of the heart. This blockade also shortens the duration of action potentials through the Purkinje fibers. Additionally, flecainide prevents delayed rectifier potassium channels from opening, lengthening the action potential in ventricular and atrial muscle fibers. It also blocks ryanodine receptor opening, reducing calcium release from the sarcoplasmic reticulum, which in turn decreases depolarization of cardiac cells.

Pharmacodynamics

Flecainide inhibits the action of sodium and potassium ion channels in the heart, raising the threshold for depolarization and correcting arrhythmias. It has a long duration of action, which allows for once daily dosing. However, due to its narrow therapeutic index, careful monitoring is required, particularly in patients with pre-existing cardiac conditions such as structural heart disease or left ventricular systolic dysfunction.

Pharmacokinetics

Flecainide is absorbed well from the gastrointestinal tract with a bioavailability of approximately 90%. It undergoes hepatic metabolism, primarily by cytochrome P450 enzymes, with a half-life ranging from 12 to 27 hours. The drug is excreted mainly in urine as metabolites, and renal function can significantly affect its clearance. Dose adjustments may be necessary in patients with impaired renal function.

Contra-indications

• Structural heart disease
• Left ventricular systolic dysfunction
• Previous hypersensitivity to flecainide

Adverse effects

• Dizziness
• Visual disturbances
• Palpitations
• Heart block
• Heart failure
• Torsades de pointes
• Seizures

Interactions

• NSAIDs: Moderate (increases exposure)
• Cimetidine: Moderate (increases exposure)
• Celecoxib: Moderate (increases exposure)
• Cobicistat: Unknown (increases concentration)
• Darifenacin: Unknown (increases concentration)
• Ritonavir: Unknown (increases exposure)

Precautions

• Monitor cardiac function regularly
• Use with caution in patients with renal impairment
• Evaluate electrolyte levels, especially potassium
• Consider potential drug interactions

Pregnancy

Flecainide should only be used if the potential benefit justifies the potential risk to the fetus. Consult relevant guidelines for more detailed information.

Breast-feeding

Flecainide is excreted in breast milk. Caution is advised when administering to nursing mothers.

Storage

Store at room temperature, away from moisture and heat. Keep out of reach of children.

Formulations

• Tablets: 50 mg, 100 mg, 150 mg

Indications

• Supraventricular arrhythmias
• Ventricular arrhythmias
• Paroxysmal supraventricular tachycardias including paroxysmal atrial flutter or fibrillation
• Re-entrant tachycardias involving the AV node or accessory pathway

Dosage

Adults: Initially, 100 mg twice daily for 3-5 days, with a maximum of 400 mg daily for rapid control or in heavily built patients; maintenance dose should be reduced to the lowest effective dose. For ventricular arrhythmias, initiate at

Mechanism of action

Flecainide acetate primarily acts as a sodium channel blocker, inhibiting the influx of sodium ions during depolarization of cardiac cells. This reduces the conduction velocity in the myocardium and prolongs the refractory period, effectively suppressing abnormal electrical activity in the heart. Its antiarrhythmic effects are particularly useful in conditions such as paroxysmal atrial fibrillation and ventricular tachycardia.

Pharmacodynamics

Flecainide demonstrates a dose-dependent effect on cardiac action potentials, notably prolonging the QRS duration on the electrocardiogram (ECG). It has a rapid onset of action and can be used for both acute and chronic management of arrhythmias. The drug's efficacy is enhanced when used in patients with structurally normal hearts; however, its use in patients with underlying heart disease carries a risk of proarrhythmia.

Pharmacokinetics

Flecainide acetate is well-absorbed from the gastrointestinal tract, with peak plasma concentrations typically occurring within 1-3 hours after oral administration. It has a high protein binding rate (approximately 95%) and is extensively metabolized in the liver, primarily by CYP2D6. The elimination half-life ranges from 12 to 27 hours, depending on individual patient factors, including hepatic function. Renal impairment may lead to increased drug accumulation, necessitating dosage adjustments.

Contra-indications

• Abnormal left ventricular function
• Atrial conduction defects (unless pacing rescue available)
• Bundle branch block (unless pacing rescue available)
• Sinus node dysfunction (unless pacing rescue available)
• History of myocardial infarction with asymptomatic ventricular ectopics
• Severe hepatic impairment

Adverse effects

• Dizziness
• Visual disturbances
• Nausea
• Ventricular tachycardia
• Heart failure
• QT interval prolongation
• Torsades de pointes
• Hypotension

Interactions

• Concurrent use of amiodarone may require dose reduction by half
• Caution with lidocaine due to possible accumulation in renal impairment

Precautions

• Monitor ECG and blood pressure regularly
• Caution in patients with a history of heart failure
• Use with caution in elderly patients (risk of accumulation)

Pregnancy

Crosses the placenta but not known to be harmful in animal studies-use if benefit outweighs risk.

Breast-feeding

Present in milk but amount too small to be harmful.

Storage

Store in a cool, dry place, away from light.

Formulations

• 50 mg tablets
• 100 mg tablets

Mechanism of action

Flecainide blocks fast inward sodium channels and slowly unbinds during diastole, prolonging the refractory period of the heart. This blockade also shortens the duration of action potentials through the Purkinjie fibers. Flecainide also prevents delayed rectifier potassium channels from opening, lengthening the action potential through ventricular and atrial muscle fibers. Finally, flecainide also blocks ryanodine receptor opening, reducing calcium release from sarcoplasmic reticulum, which reduces depolarization of cells.

Pharmacodynamics

Flecainide inhibits the action of sodium and potassium ion channels in the heart, raising the threshold for depolarization and correcting arrhythmias. Flecainide has a long duration of action, allowing for once daily dosing. The therapeutic index is narrow. Patients should not take this medication if there is already structural heart disease or left ventricular systolic dysfunction.