Use of flecainide with other sodium channel blockers is not recommended.
Treatment with Tambocor is compatible with use of oral anti-coagulants.
Flecainide can cause the plasma digoxin level rise by about 15%, which is unlikely to be of clinical significance for patients with plasma levels in the therapeutic range.
It is recommended that the digoxin plasma level in digitalised patients should be measured not less than six hours after any digoxin dose, before or after administration of flecainide.
The possibility of additive negative inotrophic effects of beta blockers and other cardiac depressants with flecainide should be recognised.
Limited data in patients receiving known enzyme inducers (phenytoin, phenobarbital, carbamazepine) indicate only 30% increase in the rate of flecainide elimination.
In healthy subjects receiving cimetidine (1 g daily) for one week, plasma flecainide levels increased by about 30% and the half life increased by 10%.
When flecainide is given in the presence of amiodarone, the usual flecainide dosage should be reduced by 50% and the patient monitored closely for adverse effects.
Plasma level monitoring is strongly recommended in these circumstances.