Interactions : אינטראקציות

4.5 Interaction with other medicinal products and other forms of interaction

It is important to consider the following interactions with this medicinal product: 
Flecainide should not be administered concomitantly with other class I antiarrhythmics or other sodium channel blockers because of the increased risk of cardiac side effects (see section 4.3).
Flecainide and other class antiarrhythmics should only be administered concomitantly if there is a tangible therapeutic effect; this requires close clinical and ECG monitoring.

In view of the possible additive effects, due caution is required for the concomitant use of flecainide and drugs with a negative inotropic or bradycardic effect, as well as drugs that slow atrioventricular or intraventricular conduction, such as beta blockers, verapamil-type calcium antagonists, cardiac glycosides or amiodarone. These interactions require a dose reduction.
The concomitant use of flecainide and propranolol can increase the flecainide plasma level by up to 20% and the propranolol plasma level by up to 30%, which may make a dose adjustment necessary for both substances.
The concomitant use of flecainide and digoxin can increase the digoxin plasma level by about 15–25%. As such, digoxin effects should be monitored clinically by repeated ECG studies or digoxin plasma level studies as appropriate. It is recommended that the digoxin plasma level in digitalised patients be measured no less than 6 hours after any digoxin dose, before or after administration of flecainide.

Diuretics produce a class effect due to potential hypokalaemia giving rise to cardiotoxicity.

Treatment with flecainide is compatible with the concomitant use of oral anticoagulants.
Life-threatening or even lethal adverse events may occur due to interactions causing increased plasma concentrations (see section 4.9).
Concurrent use of flecainide and other drugs that are also metabolised by, or that inhibit, the cytochrome P450 2D6 (CYP2D6) can slow the breakdown and increase plasma concentrations of flecainide.

Inhibitors include, for example, antidepressants, neuroleptics, propranolol, ritonavir, some antihistamines; inducers include phenytoin, phenobarbital and carbamazepine.

Enzyme inhibitors
Antiarrhythmics
Concurrent use of flecainide and amiodarone can double the flecainide plasma level, meaning that the dose of flecainide should be reduced by up to 50% (see section 4.2).

Antihistamines
Increased risk of ventricular arrhythmias with concomitant use of mizolastine and terfenadine. Avoid concomitant use.
Concurrent use of flecainide and cimetidine can double the flecainide plasma level, especially in patients with reduced kidney function (renal failure), meaning that the dose of flecainide should be reduced by up to 50% (see section 4.2).

Antiviral substances
Concurrent use of flecainide and indinavir can increase the flecainide plasma level (increased risk of ventricular arrhythmias). Avoid concomitant use.

Antidepressants
Concurrent use of flecainide and fluoxetine, paroxetine or moclobemide can increase the flecainide plasma level. Concurrent use of flecainide and tricyclics increases the risk of arrhythmias.
Neuroleptics
Concurrent use of flecainide and clozapine increases the risk of arrhythmias.

Antimalarials
Quinine and quinidine increase the plasma concentration of flecainide.

Antifungals
Terbinafine may increase plasma concentrations of flecainide.
Co-administration of bupropion, a medication to help people stop smoking that is metabolised by CYP2D6, with flecainide should be approached with caution and should use the lowest effective dose of the concomitant medication. If bupropion is added to the treatment regimen of a patient already receiving flecainide, the need to decrease the dose of the existing medication should be considered.

Enzyme inducers
Concurrent use of flecainide and known enzyme inducers (such as phenytoin, phenobarbital and carbamazepine) can increase the elimination of flecainide by up to 30%.