White, circular, biconvex tablets 6.5 mm in diameter engraved 3M on one face and TR50 on the other face. Each tablet contains flecainide acetate 50 mg. The tablet formulation is colour-free, preservative-free, sugar-free and does not contain gluten or lactose.

White, circular, biconvex tablets 8.5 mm in diameter marked 3M on one face and TR 100 over a break line on the other face. Each tablet contains flecainide acetate 100 mg. The tablet formulation is colour-free, preservative- free, sugar-free and does not contain gluten or lactose.

Grey and white hard gelatin capsules with the captions 3M and 100 printed in black ink in the axial direction on the respective capsule halves. Each capsule contains flecainide acetate 100 mg. The capsule formulation is preservative- free, sugar-free and does not contain gluten or lactose.

Grey and pink hard gelatin capsules with the captions 3M and 200 printed in black ink in the axial direction on the respective capsule halves. Each capsule contains flecainide acetate 200 mg. The capsule formulation is preservative- free, sugar-free and does not contain gluten or lactose.

Each ampoule contains flecainide acetate 150 mg in acetate buffered Water for Injections BP 15 ml. The injection formulation is colour-free, preservative- free, sugar-free and does not contain gluten or lactose.

Actions

TAMBOCOR (flecainide acetate) has local anaesthetic activity and belongs to the membrane stabilising (Class I) group of antiarrhythmic agents. It has electro-physiological effects characteristic of the IC (fast inward sodium channel blockers) class of antiarrhythmics. TAMBOCOR produces a dose related decrease in intracardiac conduction in all parts of the heart with the greatest effect on the His-Purkinje system (H-V conduction). Effects upon atrioventricular (AV) nodal conduction time and intra-atrial conduction times, although present, are less pronounced than those on ventricular conduction velocity. Significant effects on refractory periods are observed in the atria and ventricles. Sinus node recovery times (corrected) following pacing and spontaneous cycle lengths are somewhat increased. This latter effect may become significant in patients with sinus node dysfunction. TAMBOCOR affects the electrocardiograph (ECG) by widening the PR interval and by prolonging the duration of the QRS complex. The widened QRS complex (ventricular depolarisation) results in a longer QT interval but there is little specific effect on the JT interval (ventricular repolarisation). TAMBOCOR does not usually alter heart rate, although bradycardia and tachycardia have been reported occasionally. Decreases in ejection fraction, consistent with a negative inotropic effect, have been observed after single dose administration of 200 to 250 mg of flecainide in man in multiple dose studies, and exacerbations of clinical congestive heart failure (CHF) have been documented. Increases in ejection fraction may result from restoring normal rhythm.

Pharmacodynamics

In patients with symptomatic paroxysmal atrial fibrillation and flutter, TAMBOCOR prolongs the time to the first recurrence as well as the interval between recurrences of these tachyarrhythmias.

TAMBOCOR causes a dose-related and plasma-level related decrease in single and multiple premature ventricular complexes (PVCs) and chronic therapy can suppress recurrence of ventricular tachycardia. In limited studies

of patients with a history of ventricular tachycardia, flecainide has been successful 30 to 40% of the time in fully suppressing the inducibility of arrhythmias by programmed electrical stimulation.

Pharmacokinetics

Following oral administration, the absorption of flecainide from TAMBOCOR tablets is nearly complete. Peak plasma levels are reached after about three hours in most individuals (range 1 to 6 hours). Flecainide does not undergo any consequential presystemic biotransformation (first-pass effect). Food or antacids do not affect absorption. In studies of healthy subjects the apparent plasma half-life of flecainide averages 13 hours and is quite variable (range 7 to 22 hours). In studies involving patients with chronic PVCs, the apparent plasma half-life after multiple oral doses averaged about 20 hours and was also quite variable (range 12 to 27 hours). With multiple dosing, flecainide accumulates to steady-state plasma levels within 3 to 5 days, but once at steady state no additional or unexpected accumulation of drug in plasma occurs during chronic treatment. Plasma levels in an individual are approximately proportional to dose over the usual therapeutic range, deviating upwards from linearity only slightly (about 10 to 15% per 100 mg on average). TAMBOCOR CR provides prolonged and essentially complete drug absorption which allows for once daily dosing and very sustained, flat plasma level profiles. Peak plasma levels are attained after about 13 hours (range to 15.5 hours) following oral administration during long term therapy with TAMBOCOR CR. The apparent plasma half-life averages about 20 hours and is quite variable after multiple oral doses (range 12 to 27 hours). Plasma levels increase with multiple dosing, because of the long half-life, with steady- state levels being attained in 3 to 7 days. Bioavailability studies with TAMBOCOR CR capsules compared with TAMBOCOR tablets have shown that the controlled-release form of administration is almost completely bioavailable. The same study also demonstrated that steady state plasma levels of flecainide were achieved by day 5 of treatment. Changeover from TAMBOCOR tablets to TAMBOCOR CR can then be conducted without re-instigation of dose-finding. Following a single intravenous dose of TAMBOCOR injection plasma flecainide levels decrease rapidly during the initial 15 to 60 minutes distribution phase, then the rate of disappearance from plasma is relatively slow (half life 7 to 15 hours). In healthy subjects, about 30% of a single oral dose (range 10 to 50%) is excreted in urine as unchanged drug. The two major urinary metabolites are 2,5-dealkylated flecainide (active, but about one fifth as potent) and the 2,5- dealkylated lactam of flecainide (inactive metabolite). These two primarily conjugated metabolites account for most of the remaining portion of the dose. Several minor metabolites (3% of the dose or less) are also found in urine.

Only 5% of the dose is excreted in faeces. Free (unconjugated) plasma levels of the two major metabolites in patients are very low (less that 50 ng/ml). The elimination of flecainide from the body depends on renal function. With increasing renal impairment, the extent of unchanged flecainide excretion in urine is reduced and the plasma half-life of flecainide is prolonged. Elimination of flecainide in these circumstances is linked more closely to its cytochrome P450IID6 dependent hepatic metabolism. Since flecainide is extensively metabolised, there is no simple relationship between renal function, creatinine clearance and the rate of flecainide elimination from plasma. In patients with NYHA class III CHF, the rate of flecainide elimination from plasma is moderately slower (mean half-life 19 hours) than for healthy subjects (mean half-life 14 hours), but similar to the rate for patients with PVCs without CHF. The extent of excretion of unchanged drug in urine is also similar. Haemodialysis removes only about 1% of an oral dose as unchanged flecainide. The extent of flecainide binding to human plasma proteins is about 40% and is independent of plasma level over the range of 15 to about 3400 ng/ml. Clinically significant medicine interactions based on protein binding effects would therefore not be expected.

Indications

TAMBOCOR Tablets and Capsules

In patients without structural heart disease and without myocardial infarction tablets and capsules are indicated for the prevention of: Supraventricular arrhythmias

paroxysmal supraventricular tachycardias (PSVT) including atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia and other supraventricular tachycardias of unspecified mechanism associated with disabling symptoms;
paroxysmal atrial fibrillation/flutter (PAF) associated with disabling symptoms.

Ventricular arrhythmias documented life-threatening ventricular arrhythmias such as sustained ventricular tachycardia (VT) if they are considered life- threatening in the judgement of the attending physician. Not indicated for less severe ventricular arrhythmias even if symptomatic. Use of TAMBOCOR in chronic atrial fibrillation has not been adequately studied and is not recommended.

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TAMBOCOR Injection

TAMBOCOR injection is indicated in patients without structural heart disease when rapid control or short-term prophylaxis of the arrhythmias below is the main clinical requirement, including:

ventricular tachyarrhythmias where these are resistant to other treatment;
AV nodal reciprocating tachycardia, arrhythmias associated with Wolff-Parkinson-White Syndrome and similar conditions with accessory pathways;
paroxysmal atrial fibrillation in patients with disabling symptoms.

Arrhythmias of recent onset will respond more readily.

Dosage and Administration

The following regimen is suggested as a guideline. However, dosage may need to be modified as dictated by the weight, age or clinical status of the patient.

General considerations

Prior to treatment perform an adequate clinical assessment of the patient to establish that there is no structural heart disease or left ventricular systolic dysfunction. TAMBOCOR can increase pacing or defibrillation thresholds, so this should be considered when electrical devices such as pacemakers and defibrillators are used. Because TAMBOCOR slows cardiac conduction, pre-existing blocks may become more pronounced and subclinical blocks may become manifest. Correct electrolyte imbalances before treatment. These may cause or contribute to arrhythmias. Remember that impaired hepatic or renal function, including impairment associated with CHF, can contribute to elevated drug levels and necessitate special caution in dosing. The long half-life of flecainide along with the absence of a satisfactory method to remove the drug encourages one to begin dosing carefully and avoid overload with the drug. Careful gradation of dosing administration is of particular importance with TAMBOCOR CR capsules, where loading doses are specifically not recommended. It should also be noted that amiodarone may increase plasma flecainide concentrations. Treatment with TAMBOCOR should be monitored by frequent ECG recordings and/or plasma level monitoring as recommended.

TAMBOCOR tablets

For patients with paroxysmal supraventricular arrhythmias, oral TAMBOCOR therapy may be started on an outpatient basis. The recommended starting dose is 50 mg every 12 hours. The dose may be increased in increments of 50 mg b.d. at intervals of at least four days until efficacy is achieved. Most patients do not require more than 150 mg every 12 hours (300 mg/day) which is the maximum recommended daily dose. For patients with symptomatic sustained ventricular arrhythmias, oral TAMBOCOR therapy should be started in the hospital. The recommended starting dose is 100 mg every 12 hours. If clinical benefit is not achieved the dose may be increased in increments of 50 mg b.d. at intervals of at least four days until efficacy is achieved. The maximum recommended dose is 400 mg/day. Once adequate control of the arrhythmia has been achieved, it may be possible in some patients to reduce the dose as necessary to minimise side effects or effects on conduction. In such patients, efficacy at the lower dose should be evaluated. An occasional patient not adequately controlled by, or intolerant to, a dose given at 12 hour intervals may be dosed at eight hour intervals.

Amiodarone:

As for many other anti-arrhythmic agents, in the presence of amiodarone, plasma levels of flecainide may be altered. Four situations may be encountered:

and plasma level monitoring of flecainide should be done frequently. Based on therapeutic response and plasma levels, the dosage of TAMBOCOR can be adjusted accordingly. Increases in TAMBOCOR

dosage should be made carefully in increments not exceeding 50 mg b.d. and only after levels of flecainide have been obtained. If the dosage of amiodarone is changed, again carefully monitor plasma levels of flecainide and adjust TAMBOCOR dosage accordingly.

TAMBOCOR CR capsules

The overall dosage guidance follows the same general approach as the conventional tablets. Owing to the drug-specific metabolism and elimination of flecainide, an optimal effect may not be achieved in steady state conditions for patients without dose restrictions (see below and Warnings and Precautions) until after about 7 days with TAMBOCOR CR. However, in patients with dose restrictions, the time to reach steady state conditions may take 2 to 3 weeks. TAMBOCOR CR should be administered gradually. Loading doses are not recommended. TAMBOCOR CR capsules should be taken with a glass of water during or after meals. The normal recommended TAMBOCOR CR dose for patients of about 70 kg body weight is 100 mg/day. If necessary, the dose can be increased gradually using frequent ECG monitoring to a maximum of 300 mg/day. Dose increases should not exceed 100 mg. Dose increases should be made no more frequently than once every 7 days. For patients weighing considerably more or less than 70 kg, the dosage should be adjusted accordingly. Note: If a patient is changed over from TAMBOCOR tablets to TAMBOCOR CR capsules, the dosage should be based on the total daily dose (eg 2 x TAMBOCOR 100 mg tablets to TAMBOCOR CR 200 mg). A low starting dose and cautious increases of dosage with ECG and plasma level monitoring will often be necessary for patients with renal impairment. In elderly patients the initial dosage of TAMBOCOR CR should be no more than 100 mg/day. The TAMBOCOR CR dosage for patients receiving concomitant amiodarone or cimetidine therapy should generally not exceed 200 mg/day. If TAMBOCOR CR is used in patients with pacemakers, the dosage should generally not exceed 200 mg/day due to possible effects on cardiac conduction (increase of endocardial pacing thresholds).

TAMBOCOR injection

TAMBOCOR Injection should preferably be diluted with, or injected into, sterile solutions of 5% glucose. If chloride containing solutions, such as sodium chloride or Ringer's lactate are used, the injection should be added to a volume of not less than 500 ml, otherwise a precipitate will form.

TAMBOCOR Injection can be given in an emergency or for rapid effect for the cardioversion of acute atrial fibrillation or flutter, by a slow injection of 1 to 2

mg/kg over not less than 10 minutes, or in divided doses, to a maximum recommended dose of 150 mg. Dilution in 20 ml of 5% glucose is appropriate for this injection. If preferred, the dose may be diluted in a slightly larger volume of 5% glucose (eg 100 ml) and given as a mini-infusion. Continuous ECG monitoring is recommended in all patients receiving intravenous TAMBOCOR. The injection should be stopped when there is control of the arrhythmia. Similar caution should apply to patients with a history of cardiac failure, who may become decompensated during the administration. For such patients it is recommended that the initial dose be given over 30 minutes diluted in a 5% glucose infusion. For all patients, if cardioversion is not achieved during the initial slow injection/infusion, a continued infusion given at the following recommended rates can be attempted.

First hour 1.2 to 1.5 mg/kg/hour (0.02 to 0.025 mg/kg/minute). Second and later hours 0.12 to 0.25 mg/kg/hour (0.002 to 0.004 mg/kg/minute). It is recommended that the infusion duration should not exceed 24 hours, or only with extreme caution unless the oral preparation cannot be used and plasma level monitoring is available. Where treatment is considered absolutely necessary, or for patients receiving the upper end of the dose range, ECG and plasma level monitoring is strongly recommended. The maximum cumulative dose given in the first 24 hours should not exceed 600 mg. In patients with severe renal impairment (creatinine clearance <35 ml/min/1.73 m2) each of the above dosage recommendations should be reduced by half. Transition to oral dosing should be accomplished as soon as possible by stopping the infusion and administering the first required oral dose. Dosing with oral TAMBOCOR can begin with the appropriate recommended oral dose 6 to 12 hours after having ceased the infusion. Oral maintenance is then continued as indicated in the relevant oral dosage instructions.

Structural Heart Disease

Use of TAMBOCOR in the presence of structural heart disease (SHD) is not advised. SHD is defined as ventricular dysfunction or hypertrophy, symptomatic ischaemic heart disease or valvular heart disease. SHD usually would not include haemodynamically insignificant valvular heart disease, mitral valve prolapse or treated hypertension.

ECG monitoring

Frequent and long term ECG monitoring should be performed in all patients to guide dosage of TAMBOCOR. This applies to the initiation of therapy, changes in dosage and control of long term therapy with TAMBOCOR. ECG monitoring should be performed at 2 to 4 day intervals at the beginning of therapy, and particularly following dose increases. Particular attention must be paid during ECG monitoring to possible widening of the QRS complex during treatment. If QRS widening occurs by more than 25% compared to baseline, the dosage should be reduced or TAMBOCOR discontinued until the ECG reverts to normal. Frequent ECG monitoring should also be performed to guide dosage if amiodarone or cimetidine is given in combination with TAMBOCOR.

Plasma Level Monitoring

Periodic monitoring of trough plasma levels may be useful in patient management. The large majority of patients successfully treated with TAMBOCOR were found to have trough plasma levels between 200 to 1000 ng/ml. Plasma levels above 700 to 1000 ng/ml are associated with increased likelihood of adverse experiences. The probability of adverse experiences, especially cardiac adverse experiences such as conduction defects or bradycardia, may increase with higher trough plasma levels, especially when these exceed 1000 ng/ml. Recognition of the correlation of plasma levels to proarrhythmic events associated with treatment of ventricular tachycardia appears to have led to a reduced frequency and severity of such events. Plasma level monitoring is required in patients with renal failure or hepatic disease, since elimination of flecainide from plasma may be markedly slower. Dosage adjustment may be necessary. Monitoring of plasma levels is also strongly recommended in patients on concurrent amiodarone therapy and may be helpful in patients with congestive heart failure and in patients with moderate renal disease.

Children

TAMBOCOR is not recommended in children under 12 as there is insufficient evidence of its use in this age group. However, a considerable body of experiential evidence has accumulated which is strongly suggestive of the clinical effectiveness of TAMBOCOR in children of varying ages with supraventricular tachycardia but with structurally normal hearts. Similar empirical evidence of effectiveness exists for the use of TAMBOCOR in foetal tachyarrhythmias. There is an age dependent variability in the elimination half- life of flecainide in children and the available clinical evidence suggests an effective dose of TAMBOCOR in young patients, based either on body surface area or body weight, varies from 100 to 200 mg/m2/day or 1 to 8 mg/kg/day respectively. These daily doses were administered every 8 to 12 hours and adjusted according to patient age and trough plasma flecainide levels.

Elderly

From age 20 to 80, plasma flecainide levels are only slightly higher with advancing age. With usual doses the rate of flecainide elimination from plasma is somewhat slower in elderly than in younger subjects. This should be taken into consideration when making dose adjustments.

Contraindications

Warnings and Precautions

Mortality:

In the Cardiac Arrhythmia Suppression Trial (CAST), a long-term, large scale, multi-centre, double-blind, randomised, placebo-controlled clinical trial in patients with asymptomatic non-life threatening ventricular arrhythmias who had myocardial infarction more than six days but less than two years previously, oral flecainide was associated with a higher incidence of mortality or non-fatal cardiac arrest (19/323) as compared with its matching placebo (7/318). The average duration of treatment with flecainide in this study was 10 months. In that same study, an even higher incidence of mortality was observed in flecainide-treated patients with more than one myocardial infarction. While there are no comparable mortality trial data for other Class I antiarrhythmic agents post myocardial infarction, meta-analysis of small scale clinical trials of these agents in similar populations suggests a trend towards increased mortality compared to placebo. In the light of this information, it is

prudent to consider the prophylactic use of Class I antiarrhythmic drugs following myocardial infarction as potentially hazardous. Indeed, the use of these agents for other than life-threatening arrhythmias or severe symptoms due to arrhythmias, is not recommended. Comparable placebo-controlled clinical trials have not been done to determine if flecainide is associated with a higher risk of mortality in other patient groups. Structural Heart Disease: Patients with structural heart disease, treated with TAMBOCOR for supraventricular arrhythmias, may be at increased risk for proarrhythmia and cardiac adverse events. The use of TAMBOCOR in these patients has been associated with life-threatening and occasionally fatal ventricular arrhythmias. Therefore, in these patients, especially in the presence of impaired left ventricular function with ejection fraction <= 40%, TAMBOCOR should be used with extreme caution, preferably after other antiarrhythmic drugs have been tried or considered inappropriate.

Ventricular Proarrhythmic Effects in Patients with Atrial Fibrillation /Flutter:

A review of the world literature revealed reports of 568 patients treated with oral TAMBOCOR (flecainide acetate) for paroxysmal atrial fibrillation/flutter (PAF). Ventricular tachycardia was experienced in 0.4% (2/568) of these patients. Of 19 patients in the literature with chronic atrial fibrillation, 10.5% (2/19) experienced ventricular tachycardia or ventricular fibrillation.

FLECAINIDE IS NOT RECOMMENDED FOR USE IN PATIENTS WITH CHRONIC ATRIAL FIBRILLATION. Case reports of ventricular proarrhythmic effects in patients treated with TAMBOCOR for atrial fibrillation/flutter included increased premature ventricular contractions (PVCs), ventricular tachycardia (VT), ventricular fibrillation (VF) and death. As with other class I agents, patients treated with TAMBOCOR for atrial flutter have been reported with 1:1 atrioventricular conduction due to slowing of the atrial rate. A paradoxical increase in the ventricular rate also may occur in patients with atrial fibrillation who receive TAMBOCOR. Concomitant negative chronotropic therapy such as digoxin or ss-blockers may lower the risk of this complication.

Proarrhythmic Effects:

As with other antiarrhythmic drugs TAMBOCOR has been associated with the development of new or worsened arrhythmias. These so-called proarrhythmic effects may range in severity from an increase in frequency of PVCs to the development of more severe forms of ventricular tachycardia. In a few patients TAMBOCOR has been associated with episodes of unresuscitatable ventricular tachycardia or ventricular fibrillation. The incidence of proarrhythmic events was higher in studies of patients treated for recurrent ventricular tachycardia, often with coexisting congestive heart failure, than in studies of patients treated for stable ventricular ectopy. Treatment with any antiarrhythmic agent should be initiated in hospital in patients treated for recurrent sustained ventricular tachycardia, especially those with congestive heart failure or low ejection fractions. Effective use of

TAMBOCOR may be assisted in some patients by electrophysiological investigation.

Heart Failure:

Because TAMBOCOR has a mild negative inotropic effect, it may cause or worsen congestive heart failure, particularly in patients with cardiomyopathy, pre-existing severe heart failure (NYHA functional class III or

IV) or ejection fractions <= 40%. TAMBOCOR should, therefore, be used cautiously in patients who are known to have a history of congestive heart failure or myocardial dysfunction. The initial dose should be no more than 100 mg b.d. (see "Dosage and Administration") and they should be monitored carefully. Careful attention must be given to maintenance of cardiac function, including optimisation of digitalis, diuretic or other therapy. In the cases where congestive heart failure has occurred during TAMBOCOR therapy, the onset has ranged from a few hours to several months after starting therapy. Some patients who develop evidence of reduced myocardial function while on TAMBOCOR can continue on TAMBOCOR with adjustment of digitalis or diuretic, others may require dosage reduction or discontinuation of TAMBOCOR. When feasible, it is recommended that plasma flecainide levels be monitored. Attempts should be made to keep trough plasma levels below 0.7 to 1.0 ug/mL. Effects on Cardiac Conduction: TAMBOCOR slows cardiac conduction sufficiently in most patients to produce measurable increases in the duration of the PR, QRS and QT intervals on the electrocardiogram. This is an extension of the pharmacological action of the drug and most patients experience no detrimental clinical effects from these changes in conduction. Increases of more than 25% in the duration of the PR interval occur commonly and approximately one third of patients may develop first-degree heart block (PR interval greater than or equal to 0.20 seconds). Widening of the QRS of 25% or more is also common and many patients develop QRS complexes with a duration of 0.12 seconds or more. The QT (uncorrected) interval widens about 8% on the average, mostly due to the widening of the QRS. (The JT interval [QT minus QRS] is usually unaffected or widens about 4%.) Although clinically significant conduction changes such as sinus pause, sinus arrest, second or third degree AV block occasionally occur, an attempt should be made to reduce the dosage of TAMBOCOR (see "Dosage and Administration") to the lowest effective dose in an effort to minimise these effects. If second or third-degree AV block, or right bundle branch block associated with a left hemi-block occur, TAMBOCOR therapy should be discontinued unless the ventricular rate is adequately controlled by a temporary or implanted ventricular pacemaker. Sick Sinus Syndrome (Bradycardia-Tachycardia Syndrome): TAMBOCOR should not be used in patients with advanced sinus node disease and should be used only with extreme caution in patients with sick sinus syndrome because it may cause sinus bradycardia, sinus pause, or sinus arrest. Pacing rescue facilities should be available.

Digitalis Intoxication:

TAMBOCOR has not been evaluated in the treatment of arrhythmias secondary to digitalis intoxication and it increases the plasma level of digoxin (see "Interactions with Other Medicines"), therefore it is not recommended for such use.

Electrolyte Disturbances:

The presence of a potassium excess or deficit may alter the effects of Class I antiarrhythmic drugs. Any pre-existing hypokalaemia or hyperkalaemia or other electrolyte disturbances should be corrected before administration of TAMBOCOR.

Effects on Pacemaker Thresholds:

TAMBOCOR is known to reversibly increase endocardial pacing thresholds and may suppress ventricular escape rhythms. It should 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. It is suggested that the threshold in patients with pacemakers be determined prior to instituting therapy with TAMBOCOR, again after one week of administration and at regular intervals thereafter. Generally threshold changes are within the range of multi- programmable pacemakers and when these changes occur, usually a doubling of either voltage or pulse width is sufficient to regain capture.

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 co-administration with TAMBOCOR are unknown. Neither disopyramide nor verapamil should be administered concurrently with TAMBOCOR, unless, in the judgement of the physician, the benefit of this combination outweighs the risks. 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 judgement of the physician the benefits outweigh the risks and TAMBOCOR is to be administered in the presence of amiodarone, the dose of TAMBOCOR should be reduced (see "Dosage and Administration") with plasma flecainide monitoring.

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.

Alkaline Urine:

In the presence of alkaline urine (pH greater than 7.0) which may result from diet, concomitant medication or disease states, TAMBOCOR elimination may be slower, as has also been reported for other basic compounds and TAMBOCOR dosage may need to be reduced.

Renal or Hepatic Impairment:

Manifest hepatic functional impairment (liver failure) or renal impairment requires particular caution during treatment with TAMBOCOR.

A lower starting dose at half the usual dosing recommendations, cautious increases of dosage and plasma level monitoring will often be necessary for patients with significant renal disease (creatinine clearance of <35 ml/min/1.73 m2). In patients with less severe renal disease the initial dosage may be as great as 100 mg every 12 hours. When used in such patients, frequent plasma level monitoring is strongly recommended to guide dosage adjustments. In both groups of patients, dosage increases should be made very cautiously when plasma levels have plateaued (after more than four days with TAMBOCOR tablets), observing the patient closely for signs of adverse cardiac effects or other toxicity. Since elimination of flecainide from plasma can be markedly slower in patients with significant hepatic impairment, treatment with TAMBOCOR should not be used in such patients unless the potential benefits clearly outweigh the risks. If used, frequent and early plasma flecainide level monitoring is required to guide dosage and increases should be made very cautiously when plasma levels have reached a plateau. It should be borne in mind that in patients with renal or hepatic impairment, it may take longer than four days before a new steady-state plasma level is reached following a dosage change.

Cytochrome P450IID6 Metabolism:

The biotransformation of flecainide is catalysed by cytochrome P450IID6 and is subject to genetic polymorphism. This is further complicated by the influence of renal excretion. In poor metabolisers, especially those with renal impairment, flecainide will tend to reach higher plasma concentrations. However, in extensive metabolisers, again especially in subjects with renal impairment, drugs that inhibit cytochrome P450IID6 might increase the plasma concentrations of flecainide during chronic therapy. Furthermore, flecainide is itself an inhibitor of cytochrome P450IID6 and may contribute to such increases in its own plasma levels.

Use in Pregnancy (Category B3):

Flecainide has been shown to have teratogenic effects (eg. club paws, sternebral and vertebral abnormalities, pale hearts with contracted ventricular septa) and an embryotoxic effect (eg. increased resorptions) in one breed of rabbit (New Zealand White) but not in another (Dutch Belted), when given in doses about four times (but not three times) the usual human dose (assuming a patient weight of 50 kg). No teratogenic effects were observed in rats or mice given doses up to 50 and 80 mg/kg/day, respectively, however, delayed sternebral and vertebral ossification was observed at the high dose in rats. Although the significance of these findings to humans is uncertain, since there is no information on the effect on the human foetus, TAMBOCOR should not be used during pregnancy unless as a drug of last resort in life-threatening arrhythmias.

Labour and Delivery:

It is not known whether the use of TAMBOCOR during labour or delivery has immediate or delayed adverse effects on the mother or foetus, affects the duration of labour or delivery or increases the possibility of forceps delivery or other obstetrical intervention.

Use in Lactation:

No specific studies are available to determine the excretion of TAMBOCOR in human breast milk. However, limited data indicate that flecainide is excreted in breast milk. The benefit of TAMBOCOR during lactation should therefore be weighed against possible effects on the child.

Interactions with Other Medicines:

During multiple oral dosage of TAMBOCOR to healthy subjects stabilised on a maintenance dose of digoxin, a 13% +- 19% increase in plasma digoxin levels occurred at six hours post dose. These small changes in digoxin levels should be of no clinical consequence for patients receiving chronic digoxin therapy. TAMBOCOR has been administered to patients receiving digitalis preparation without adverse effects.

ss-adrenergic blocking agents: TAMBOCOR has been administered to patients receiving ss-adrenergic blocking agents without adverse effects. In a formal interaction study conducted in healthy males receiving TAMBOCOR and propranolol concurrently, plasma TAMBOCOR levels were about 20% higher and propranolol levels about 30% higher, in comparison to control values. These small changes should be of no clinical consequence. In this study, TAMBOCOR and propranolol were each found to have slight negative inotropic effects on cardiac function; when administered together these effects were never any more than additive. The effects of concomitant administration of TAMBOCOR and propranolol on the PR interval were less than additive. While these effects were of little clinical consequence in healthy subjects, the possibility of exaggerated effects from this combination in patients with reduced left ventricular function should be borne in mind. In TAMBOCOR clinical trials, patients who were receiving ss-blockers concurrently did not experience an increased incidence of side effects. Nevertheless, the possibility of additive negative inotropic effects of ss-blockers and flecainide should be recognised.

There has been too little experience with the co- administration of TAMBOCOR with nifedipine or diltiazem to recommend concomitant use.

TAMBOCOR has been used in large numbers of patients receiving diuretics without apparent interactive effects.

In healthy subjects receiving cimetidine (1 g daily) for one week, plasma flecainide levels increased by about 30% and half-life increased by about 10%.

Although formal interaction studies have not been conducted with TAMBOCOR and other drugs, TAMBOCOR is not extensively bound to plasma proteins and consequently interactions with other drugs which are highly protein bound (eg. anticoagulants) would not be expected.

Limited data in patients receiving known enzyme inducers (phenytoin, phenobarbital, carbamazepine) indicate only a 30% increase in the rate of flecainide elimination.

Blood Dyscrasias:

There have been extremely rare reports of blood dyscrasias (pancytopenia, anaemia, thrombocytopenia, leukopenia, granulocytopenia) Although no causal relationship has been established, it is advisable to discontinue TAMBOCOR in patients who develop blood dyscrasias in order to eliminate TAMBOCOR as the possible causative agent.

Lung Disease:

There have been very rare reports of lung disease (pulmonary fibrosis, interstitial lung disease and pneumonitis). Although no causal relationship has been established, it is advisable to discontinue TAMBOCOR in patients who develop lung disease in order to eliminate TAMBOCOR as the possible causative agent.

Occupational Hazards:

Since TAMBOCOR can cause dizziness, light headedness, faintness and visual disturbance, patients should be cautioned about engaging in activities requiring judgement and physical coordination (such as driving an automobile or operating dangerous machinery) when these effects occur.

ADVERSE EFFECTS

TAMBOCOR has been evaluated in 1,224 patients participating in clinical trials which included both life threatening and non-life threatening ventricular arrhythmias. The most serious adverse reactions reported for TAMBOCOR in patients with ventricular arrhythmias were new or exacerbated ventricular arrhythmias which occurred in 6.8% of patients and new or worsened congestive heart failure which occurred in 3.9% of patients. In some patients, TAMBOCOR treatment has been associated with episodes of unresuscitatable ventricular tachycardia or ventricular fibrillation. There have also been instances of second- (0.5%) or third-degree (0.4%) AV block. A total of 1.2% of patients developed sinus bradycardia, sinus pause, or sinus arrest (see "Warnings and Precautions"). The frequency of most of these serious adverse reactions probably increases with higher trough plasma levels, especially when these trough levels exceed 1.0 ug/mL.

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The most commonly reported non-cardiac reactions experienced by patients with ventricular arrhythmias were dizziness 27%, visual disturbance 26% (includes blurred vision, diplopia, visual field effects, photophobia), headache 10%, nausea 10% and dyspnoea 9%. Other adverse reactions occurring in over 3% of the patients in clinical trials: Body as a Whole - fatigue 7%, asthenia 5%; Cardiovascular - palpitations 6%, chest pain 6.%; Gastrointestinal - constipation 4%, abdominal pain 3%; Nervous System - tremor 6%, nervousness 3%, paraesthesia 3%; Skin - rash 4%. The following additional adverse reactions, possibly related to TAMBOCOR therapy and occurring in 1 to less than 3% of patients have been reported in clinical trials: Body as a Whole - pain, increased sweating, flushing, dry mouth, swollen lips, tongue and mouth, eye pain and irritation, arthralgia, fever, myalgia, hemiparesis, weakness; Cardiovascular - oedema, syncope, tachycardia, angina pectoris, conduction disturbance; Gastrointestinal - vomiting, diarrhoea, anorexia; Nervous System - hypoaesthesia, somnolence, insomnia, ataxia, depression; Respiratory - coughing; Skin - pruritus;

Special Senses - tinnitus; Urinary System - micturition disorder (includes urinary retention, frequency, polyuria, dysuria). The following additional adverse experiences, possibly related to TAMBOCOR, have been reported in less than 1% of patients: Body as a Whole - impotence, decreased libido, gynaecomastia, malaise, vertigo; Cardiovascular - bradycardia, EC abnormality, hypertension, hypotension, heart disorder, myocardial infarction, peripheral ischaemia, pulmonary oedema; Gastrointestinal - dyspepsia, flatulence, GI haemorrhage; Nervous System - anxiety, twitching, convulsions, nystagmus, stupor, dysphonia, speech disorder, coma, amnesia, confusion, depersonalisation, hallucination, paranoid reaction, euphoria, apathy, morbid dreams; Respiratory - bronchospasm, laryngismus; Skin - dermatitis, hypertrichosis, photosensitivity reaction, skin discolouration; Special Senses - deafness, parosmia, loss of taste, taste perversion; Urinary System - renal failure, haematuria;

Laboratory Abnormalities

- hyperglycaemia, increased nonprotein nitrogen, increased serum alkaline phosphatase, increased serum SGPT and SGOT. Patients with elevations of liver function tests have been asymptomatic and no cause and effect relationship with TAMBOCOR has been established.

Adverse reactions leading to discontinuation of therapy occurred in 18.5% of the patients. The two most common were non-cardiac adverse reactions 9.0% and new or worsened arrhythmias 6.8%. TAMBOCOR has been evaluated in 225 patients with supraventricular arrhythmias. The most serious adverse reactions reported for TAMBOCOR in patients with supraventricular arrhythmias were new or worsened supraventricular or ventricular arrhythmias which were reported in 4% of patients (see "Warnings and Precautions"), conduction disturbance which occurred in 2% of patients and new or worsened congestive heart failure which occurred in 0.4% of patients. The most commonly reported non-cardiac adverse reactions for supraventricular arrhythmia patients remain consistent with those known for

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patients treated with TAMBOCOR for ventricular arrhythmias: vision disturbance 38%, dizziness 37%, headache 18%, nausea 18%, dyspnoea 13%, fatigue 13%, chest pain 12%, palpitations 11%. Although these incidences are higher than those reported in ventricular arrhythmia patients it is difficult to compare supraventricular and ventricular data bases because many of the supraventricular arrhythmia patients were dosed to tolerance in the clinical trials. In postmarketing surveillance experience, there have been rare reports of hepatic dysfunction including reports of cholestasis and hepatic failure, very rare reports of pulmonary fibrosis, interstitial lung disease and pneumonitis, and extremely rare reports of blood dyscrasias (see "Warnings and Precautions"). Although no cause and effect relationship has been established, it is advisable to discontinue TAMBOCOR in these patients in order to eliminate TAMBOCOR as the possible causative agent.

Cardiovascular/pro-arrhythmic effects

Pro-arrhythmic effects occur but are most likely in patients with structural heart disease and/or significant left ventricular impairment. AV heart block, angina pectoris, hypertension and hypotension have been reported. The most serious adverse effects reported for TAMBOCOR are new or exacerbated ventricular arrhythmias and new or worsened congestive heart failure. In some patients, flecainide treatment has been associated with episodes of unresuscitatable ventricular tachycardia or ventricular fibrillation. Rare occurrences of second or third-degree AV block, sinus bradycardia, sinus pause or sinus arrest have been reported. In patients with atrial flutter the use of TAMBOCOR has been associated with 1:1 AV conduction following initial atrial slowing with resultant ventricular acceleration. This has been seen most commonly following the use of TAMBOCOR Injection for conversion of acute arrhythmias. This effect is usually short lived and abates quickly following cessation of therapy.

Overdosage

Clinical Features:

No data are available concerning overdosage of TAMBOCOR in humans. However, animal studies suggest the following events may occur: lengthening of the PR interval; increases in the QRS duration, QT interval and amplitude of the T-wave; a reduction in myocardial rate and contractility; conduction disturbances; hypotension; and death from respiratory failure or asystole.

Management:

Treatment of overdosage should be supportive and may include the following: administration of inotropic agents or cardiac stimulants such as dopamine, dobutamine or isoprenaline; mechanically assisted

respiration; circulatory assistance such as intra-aortic balloon pumping and transvenous pacing in the event of conduction block. Because of the long plasma half-life of TAMBOCOR (range from 12 to 27 hours in patients), these supportive treatments may need to be continued for extended periods of time. Haemodialysis is not an effective means of removing TAMBOCOR from the body. For the treatment of TAMBOCOR overdose when urine is clearly alkaline, acidification of urine (eg. with ammonium chloride) may promote TAMBOCOR elimination. When urine is not clearly alkaline, it may be of some benefit to empirically acidify the urine in severe overdose cases.

Pharmaceutical Precautions

Storage conditions

TAMBOCOR tablets and TAMBOCOR CR capsules should be stored below 30degC. TAMBOCOR injection should be protected from light and stored between 5degC and 30degC. Do not freeze.

Medicine Classification

Package Quantities

Further Information

Name and Address

iNova Pharmaceuticals (New Zealand) Limited C/o Simpson Grierson 88 Shortland Street Auckland Distributed by: Douglas Pharmaceuticals Limited, Auckland Telephone: (09) 835 0660; Facsimile: (09) 835 0685

Flecainide acetate 50 mg and 100 mg tablets

Flecainide acetate 100 mg and 200 mg modified release capsules

Flecainide acetate 10 mg/ml intravenous injection

Presentation

Uses