Electrolyte disturbances should be corrected before using Flecainide acetate (Tambocor). Since flecainide elimination from the plasma can be markedly slower, in patients with significant hepatic impairment, flecainide should not be used in such patients unless the potential benefits clearly outweigh the risks.
Plasma level monitoring strongly recommended in these circumstances.
Flecainide acetate (Tambocor) is known to increase endocardial pacing thresholds - i.e. to decrease endocardial pacing sensitivity. This effect is reversible and is more marked on the acute pacing threshold than on the chronic.
Flecainide acetate (Tambocor) should thus be used with caution in all patients with permanent pacemakers or temporary pacing electrodes, and should not be administered to patients with existing poor thresholds or non-programmable pacemakers unless suitable pacing rescue is available.
Generally, a doubling of either pulse width or current is sufficient to regain capture, but it may be difficult to obtain ventricular thresholds less than 1 volt at initial implantation in the presence of Flecainide acetate (Tambocor).
The minor negative inotropic effect of flecainide may assume importance in patients predisposed to cardiac failure.
Difficulty has been experienced in defibrillating some patients. Most of the cases reported had pre-existing heart disease with cardiac enlargement, a history of myocardial infarction, arterio-sclerotic heart disease and cardiac failure.
Concomitant antiarrhythmic therapy. Due to limited exposure, the concomitant use of Tambocor and other antiarrhythmic agents is not recommended.
Both disopyramide and verapamil have negative inotropic properties and the effects of coadministration with Tambocor are unknown. Neither disopyramide nor verapamil should be administered concurrently with Tambocor unless, in the judgment of the doctor, the benefit of this combination outweighs the risk.
Formal interaction studies have not been conducted with amiodarone and Tambocor. However clinical experience indicates, as for many other antiarrhythmic agents, that amiodarone can increase plasma levels of flecainide.
If, in the judgment of the doctor, the benefits outweigh the risks and Tambocor is to be administered in the presence of amiodarone, the dose of Tambocor should be reduced with plasma flecainide monitoring.
Lignocaine has been used occasionally with Tambocor while awaiting the therapeutic effect of Tambocor. No adverse drug interactions were apparent.
However, no studies have been performed to demonstrate the usefulness of this regimen.
Recommendations for initiation of treatment: For patients with paroxysmal supraventricular arrhythmias, oral flecainide therapy may be started on an outpatient basis.
For patients with symptomatic sustained ventricular tachycardia, oral flecainide therapy should be started in the hospital.
For patients with premature ventricular contractions and/or non-sustained ventricular tachycardia causing disabling symptoms, a decision regarding outpatient or inpatient initiation of oral flecainide therapy must be based upon the physician's assessment of the individual patient.