CONCOMITANT ADMINISTRATION OF FLECAINIDE WITH OTHER ANTIARRHYTHMICS OR ARRHYTHMOGENIC DRUGS MAY INCREASE THE INCIDENCE OF CARDIAC ARRHYTHMIAS & MYOCARDIAL DEPRESSION. CONCOMITANT USE WITH BETA BLOCKER PRODUCES ADDITIVE NEGATIVE INOTROPIC EFFECTS. IT UNDERGOES METABOLISM IN THE LIVER AND ITS ACTIVITY MAY BE INFLUENCED BY THE DRUGS AFFECTING THE ENZYMES RESPONSIBLE FOR ITS METABOLISM. MILK FEED IN CHILD REDUCED ABSORPTION OF FLECAINIDE FROM THE GUT. CARDIAC TOXICITY OF FLECAINIDE IS INCREASED IF HYPOKALEMIA OCCURE BY THE USE OF DIURETICS. AMIODARONE INCREASES PLASMA FLECAINIDE LEVELS( HALF FLECAINIDE DOSE). TRICYCLIC ANTIDEPRESSANTS, CLOZAPINE( & OTHER ANTIPSYCHOTICS), MIZOLASTINE, TERFENADINE MAY INCREASE THE RISK OF VENTRICULAR ARRHYTHMIAS. ARTEMETHER WITH LUMEFANTRINE MAY ALSO INCREASE RISK OF VENTRICULAR ARRHYTHMIA. CIMETIDINE INCREASES PLASMA LEVELS DUE TO DECREASED METABOLISM. VERAPAMIL & AMIODARONE MAY CAUSE INCREASED MYOCARDIAL DEPRESSION. AMIODARONE HAS LONG HALF LIFE, THERE IS A POTENTIAL FOR DRUG INTERACTIONS TO OCCUR SEVERAL WEEKS OR EVEN MONTHS AFTER TREATMENT WITH IT HAS STOPPED. QUININE, FLUOXETINE & RITONAVIR INCREASE PLASMA FLECAINIDE LEVELS. BRETYLIUM, BUPIVACAINE, DISOPYRAMIDE, PROPAFENONE,QUINIDINE - INCREASED RISK OF MYOCARDIAL DEPRESSION. INCREASED RISK OF SIDE EFFECTS WITH MYELOSUPPRESSIVE DRUGS. AVOID CONCOMITANT USE WITH DRUGS ASSOCIATED WITH A SUBSTANTIAL POTENTIAL FOR CAUSING AGRANULOCYTOSIS.