No specific antidote has been identified for the treatment of flecainide overdosage. Overdoses ranging up to 8000 mg have been survived, with peak plasma flecainide concentrations as high as 5.3 mcg/mL. Untoward effects in these cases included nausea and vomiting, convulsions, hypotension, bradycardia, syncope, extreme widening of the QRS complex, widening of the QT interval, widening of the PR interval, ventricular tachycardia, AV nodal block, asystole, bundle branch block, cardiac failure and cardiac arrest. The spectrum of events observed in fatal cases was much the same as that seen in the non-fatal cases. Death has resulted following ingestion of as little as 1000 mg; concomitant overdose of other drugs and/or alcohol in many instances undoubtedly contributed to the fatal outcome. Treatment of overdosage should be supportive and may include the following: removal of unabsorbed drug from the gastrointestinal tract, administration of inotropic agents or cardiac stimulants such as dopamine, dobutamine or isoproterenol; mechanically assisted respiration; circulatory assists such as intra-aortic balloon pumping; and transvenous pacing in the event of conduction block. Because of the long plasma half-life of flecainide (12 to 27 hours in patients receiving usual doses), and the possibility of markedly non-linear elimination kinetics at very high doses, these supportive treatments may need to be continued for extended periods of time.
Hemodialysis is not an effective means of removing flecainide from the body. Since flecainide elimination is much slower when urine is very alkaline (pH 8 or higher), theoretically, acidification of urine to promote drug excretion may be beneficial in overdose cases with very alkaline urine. There is no evidence that acidification from normal urinary pH increases excretion.
For patients with sustained VT, no matter what their cardiac status, flecainide, like other antiarrhythmics, should be initiated in hospital with rhythm monitoring.
Flecainide has a long half-life (12 to 27 hours in patients). Steady-state plasma levels, in patients with normal renal and hepatic function, may not be achieved until the patient has received 3 to 5 days of therapy at a given dose. Therefore, increases in dosage should be made no more frequently than once every four days , since during the first 2 to 3 days of therapy the optimal effect of a given dose may not be achieved.
For patients with PSVT and patients with PAF the recommended starting dose is 50 mg every 12 hours. Flecainide acetate doses may be increased in increments of 50 mg bid every four days until efficacy is achieved. For PAF patients, a substantial increase in efficacy without a substantial increase in discontinuations for adverse experiences may be achieved by increasing the flecainide acetate dose from 50 to 100 mg bid. The maximum recommended dose for patients with paroxysmal supraventricular arrhythmias is 300 mg/day.
For sustained VT the recommended starting dose is 100 mg every 12 hours. This dose may be increased in increments of 50 mg bid every four days until efficacy is achieved. Most patients with sustained VT do not require more than 150 mg every 12 hours (300 mg/day), and the maximum dose recommended is 400 mg/day.
In patients with sustained VT, use of higher initial doses and more rapid dosage adjustments have resulted in an increased incidence of proarrhythmic events and CHF, particularly during the first few days of dosing (see WARNINGS). Therefore, a loading dose is not recommended.
Intravenous lidocaine has been used occasionally with flecainide while awaiting the therapeutic effect of flecainide. No adverse drug interactions were apparent. However, no formal studies have been performed to demonstrate the usefulness of this regimen.
An occasional patient not adequately controlled by (or intolerant to) a dose given at 12-hour intervals may be dosed at eight-hour intervals.
Once adequate control of the arrhythmia has been achieved, it may be possible in some patients to reduce the dose as necessary to minimize side effects or effects on conduction. In such patients, efficacy at the lower dose should be evaluated.
Flecainide should be used cautiously in patients with a history of CHF or myocardial dysfunction (see WARNINGS).
Any use of flecainide in children should be directly supervised by a cardiologist skilled in the treatment of arrhythmias in children. Because of the evolving nature of information in this area, specialized literature should be consulted. Under six months of age, the initial starting dose of flecainide acetate in children is approximately 50 mg/M2 body surface area daily, divided into two or three equally spaced doses. Over six months of age, the initial starting dose may be increased to 100 mg/M2 per day. The maximum recommended dose is 200 mg/M2 per day. This dose should not be exceeded. In some children on higher doses, despite previously low plasma levels, the level has increased rapidly to far above therapeutic values while taking the same dose. Small changes in dose may also lead to disproportionate increases in plasma levels. Plasma trough (less than one hour pre-dose) flecainide levels and electrocardiograms should be obtained at presumed steady state (after at least five doses) either after initiation or change in flecainide dose, whether the dose was increased for lack of effectiveness, or increased growth of the patient. For the first year on therapy, whenever the patient is seen for reasons of clinical follow-up, it is suggested that a 12-lead electrocardiogram and plasma trough flecainide level are obtained. The usual therapeutic level of flecainide in children is 200 to 500 ng/mL. In some cases, levels as high as 800 ng/mL may be required for control.
In patients with severe renal impairment (creatinine clearance of 35 mL/min/1.73 square meters or less), the initial dosage should be 100 mg once daily (or 50 mg bid); when used in such patients, frequent plasma level monitoring is required to guide dosage adjustments (see Plasma Level Monitoring). In patients with less severe renal disease, the initial dosage should be 100 mg every 12 hours; plasma level monitoring may also be useful in these patients during dosage adjustment. In both groups of patients, dosage increases should be made very cautiously when plasma levels have plateaued (after more than four days), observing the patient closely for signs of adverse cardiac effects or other toxicity. It should be borne in mind that in these patients it may take longer than four days before a new steady-state plasma level is reached following a dosage change.
Based on theoretical considerations, rather than experimental data, the following suggestion is made: when transferring patients from another antiarrhythmic drug to flecainide allow at least two to four plasma half-lives to elapse for the drug being discontinued before starting flecainide at the usual dosage. In patients where withdrawal of a previous antiarrhythmic agent is likely to produce life-threatening arrhythmias, the physician should consider hospitalizing the patient.
When flecainide is given in the presence of amiodarone, reduce the usual flecainide dose by 50% and monitor the patient closely for adverse effects. Plasma level monitoring is strongly recommended to guide dosage with such combination therapy (see below).
The large majority of patients successfully treated with flecainide were found to have trough plasma levels between 0.2 and 1 mcg/mL. The probability of adverse experiences, especially cardiac, may increase with higher trough plasma levels, especially when these exceed 1 mcg/mL. Periodic monitoring of trough plasma levels may be useful in patient management. Plasma level monitoring is required in patients with severe renal failure or severe hepatic disease, since elimination of flecainide from plasma may be markedly slower. Monitoring of plasma levels is strongly recommended in patients on concurrent amiodarone therapy and may also be helpful in patients with CHF and in patients with moderate renal disease.
Flecainide Acetate Tablets, USP are available as follows:
50 mg: White, round tablets debossed with “AN” above “641” on one side and plain on other side.
Bottles of 100: NDC 53746-641-01
Bottles of 1000: NDC 53746-641-10
100 mg: White, round tablets debossed with “AN” above “642” with a single-line bisect separating them on one side and plain on other side.
Bottles of 100: NDC 53746-642-01
Bottles of 1000: NDC 53746-642-10
150 mg: White, oval tablets debossed with “AN”, “643” with a single-line bisect separating them on one side and plain on other side.
Bottles of 100: NDC 53746-643-01
Bottles of 1000: NDC 53746-643-10
Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].
Store in a tight, light-resistant container.
Amneal Pharmaceuticals Pvt. Ltd.
Ahmedabad 382220, INDIA
Amneal Pharmaceuticals LLC
Bridgewater, NJ 08807
All MedLibrary.org resources are included in as near-original form as possible, meaning that the information from the original provider has been rendered here with only typographical or stylistic modifications and not with any substantive alterations of content, meaning or intent.