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TIKOSYN®
(dofetilide)
Capsules

To minimize the risk of induced arrhythmia, patients initiated or re-initiated on TIKOSYN should be placed for a minimum of 3 days in a facility that can provide calculations of creatinine clearance, continuous electrocardiographic monitoring, and cardiac resuscitation. For detailed instructions regarding dose selection, see DOSAGE AND ADMINISTRATION. TIKOSYN is available only to hospitals and prescribers who have received appropriate TIKOSYN dosing and treatment initiation education, see DOSAGE AND ADMINISTRATION.

DESCRIPTION

TIKOSYN (dofetilide) is an antiarrhythmic drug with Class III (cardiac action potential duration prolonging) properties. Its empirical formula is C19H27N3O5S2 and it has a molecular weight of 441.6. The structural formula is

The chemical name for dofetilide is N-[4-[2-[methyl[2-[4-[(methylsulfonyl)amino]phenoxy]ethyl]amino]ethyl]phenyl]-methanesulfonamide.

Dofetilide is a white to off-white powder. It is very slightly soluble in water and propan-2-ol and is soluble in 0.1M aqueous sodium hydroxide, acetone and aqueous 0.1M hydrochloric acid.

TIKOSYN capsules contain the following inactive ingredients: microcrystalline cellulose, corn starch, colloidal silicon dioxide and magnesium stearate. TIKOSYN is supplied for oral administration in three dosage strengths: 125 mcg (0.125 mg) orange and white capsules, 250 mcg (0.25 mg) peach capsules, and 500 mcg (0.5 mg) peach and white capsules.

CLINICAL PHARMACOLOGY

Mechanism of Action

TIKOSYN (dofetilide) shows Vaughan Williams Class III antiarrhythmic activity. The mechanism of action is blockade of the cardiac ion channel carrying the rapid component of the delayed rectifier potassium current, IKr. At concentrations covering several orders of magnitude, dofetilide blocks only IKr with no relevant block of the other repolarizing potassium currents (e.g., IKs, IK1). At clinically relevant concentrations, dofetilide has no effect on sodium channels (associated with Class I effect), adrenergic alpha-receptors, or adrenergic beta-receptors.

Electrophysiology

TIKOSYN (dofetilide) increases the monophasic action potential duration in a predictable, concentration-dependent manner, primarily due to delayed repolarization. This effect, and the related increase in effective refractory period, is observed in the atria and ventricles in both resting and paced electrophysiology studies. The increase in QT interval observed on the surface ECG is a result of prolongation of both effective and functional refractory periods in the His-Purkinje system and the ventricles.

Dofetilide did not influence cardiac conduction velocity and sinus node function in a variety of studies in patients with or without structural heart disease. This is consistent with a lack of effect of dofetilide on the PR interval and QRS width in patients with pre-existing heart block and/or sick sinus syndrome.

In patients, dofetilide terminates induced re-entrant tachyarrhythmias (e.g., atrial fibrillation/flutter and ventricular tachycardia) and prevents their re-induction. TIKOSYN does not increase the electrical energy required to convert electrically-induced ventricular fibrillation, and it significantly reduces the defibrillation threshold in patients with ventricular tachycardia and ventricular fibrillation undergoing implantation of a cardioverter-defibrillator device.

Hemodynamic Effects

In hemodynamic studies, TIKOSYN had no effect on cardiac output, cardiac index, stroke volume index, or systemic vascular resistance in patients with ventricular tachycardia, mild to moderate congestive heart failure or angina and either normal or low left ventricular ejection fraction. There was no evidence of a negative inotropic effect related to TIKOSYN therapy in patients with atrial fibrillation. There was no increase in heart failure in patients with significant left ventricular dysfunction (see Safety in Patients with Structural Heart Disease: DIAMOND Studies). In the overall clinical program, TIKOSYN did not affect blood pressure. Heart rate was decreased by 4-6 bpm in studies in patients.

Pharmacokinetics, General

Pharmacokinetics in Special Populations

Drug-Drug Interactions

Dose-Response and Concentration Response for Increase in QT Interval

Increase in QT interval is directly related to dofetilide dose and plasma concentration. Figure 1 shows that the relationship in normal volunteers between dofetilide plasma concentrations and change in QTc is linear, with a positive slope of approximately 15–25 msec/(ng/mL) after the first dose and approximately 10–15 msec/(ng/mL) at Day 23 (reflecting a steady state of dosing). A linear relationship between mean QTc increase and dofetilide dose was also seen in patients with renal impairment, in patients with ischemic heart disease, and in patients with supraventricular and ventricular arrhythmias.

Figure 1: Mean QTc-Concentration Relationship in Young Volunteers Over 24 Days.

Note: The range of dofetilide plasma concentrations achieved with the 500 mcg BID dose adjusted for creatinine clearance is 1–3.5 ng/mL.

The relationship between dose, efficacy and the increase in QTc from baseline at steady state for the two randomized, placebo-controlled studies (described further below) is shown in Figure 2. The studies examined the effectiveness of TIKOSYN in conversion to sinus rhythm and maintenance of normal sinus rhythm after conversion in patients with atrial fibrillation/flutter of >1 week duration. As shown, both the probability of a patient's remaining in sinus rhythm at six months and the change in QTc from baseline at steady state of dosing increased in an approximately linear fashion with increasing dose of TIKOSYN. Note that in these studies doses were modified by results of creatinine clearance measurement and in-hospital QTc prolongation.

                                          Number of patients evaluated for maintenance of NSR: 503 TIKOSYN, 174 placebo.
                                          Number of patients evaluated for QTc change: 478 TIKOSYN, 167 placebo.

Figure 2: Relationship Between TIKOSYN Dose, QTc Increase and Maintenance of NSR.

CLINICAL STUDIES

Chronic Atrial Fibrillation and/or Atrial Flutter

Two randomized, parallel, double-blind, placebo controlled, dose-response trials evaluated the ability of TIKOSYN 1) to convert patients with atrial fibrillation or atrial flutter (AF/AFl) of more than 1 week duration to normal sinus rhythm (NSR) and 2) to maintain NSR (delay time to recurrence of AF/AFl) after drug-induced or electrical cardioversion. A total of 996 patients with a one week to two year history of atrial fibrillation/atrial flutter were enrolled. Both studies randomized patients to placebo or to doses of TIKOSYN 125 mcg, 250 mcg, 500 mcg or in one study a comparator drug, given twice a day (these doses were lowered based on calculated creatinine clearance and, in one of the studies, for QT interval or QTc). All patients were started on therapy in a hospital where their ECG was monitored (see DOSAGE AND ADMINISTRATION).

Patients were excluded from participation if they had had syncope within the past 6 months, AV block greater than first degree, MI or unstable angina within 1 month, cardiac surgery within 2 months, history of QT interval prolongation or polymorphic ventricular tachycardia associated with use of anti-arrhythmic drugs, QT interval or QTc >440 msec, serum creatinine >2.5 mg/mL, significant diseases of other organ systems; used cimetidine; or used drugs known to prolong the QT interval.

Both studies enrolled mostly Caucasians (over 90%), males (over 70%) and patients ≥65 years of age (over 50%). Most (>90%) were NYHA Functional Class I or II. Approximately one-half had structural heart disease (including ischemic heart disease, cardiomyopathies, and valvular disease) and about one-half were hypertensive. A substantial proportion of patients were on concomitant therapy, including digoxin (over 60%), diuretics (over 20%) and ACE inhibitors (over 30%). About 90% were on anticoagulants.

Acute conversion rates are shown in Table 1 for randomized doses (doses were adjusted for calculated creatinine clearance and, in Study 1, for QT interval or QTc). Of patients who converted pharmacologically, approximately 70% converted within 24–36 hours.

Table 1: Conversion of Atrial Fibrillation/Flutter to Normal Sinus Rhythm
TIKOSYN Dose
125 mcg
BID
250 mcg
BID
500 mcg
BID
Placebo
Study 15/82(6%)8/82(10%)23/77(30%)1/84(1%)
Study 28/135(6%)14/133(11%)38/129(29%)2/137(1%)

Patients who did not convert to NSR with randomized therapy within 48–72 hours had electrical cardioversion. Those patients remaining in NSR after conversion in hospital were continued on randomized therapy as outpatients (maintenance period) for up to one year unless they experienced a recurrence of atrial fibrillation/atrial flutter or withdrew for other reasons.

Table 2 shows, by randomized dose, the percentage of patients at 6 and 12 months in both studies, who remained on treatment in NSR and the percentage of patients who withdrew because of recurrence of AF/AFl or adverse events.

Table 2: Patient Status at 6 and 12 Months Post Randomization
TIKOSYN Dose
125 mcg BID250 mcg BID500 mcg BIDPlacebo
Please note that columns do not add up to 100% due to discontinuations for "other" reasons.
Study 1
Randomized82827784
Achieved NSR60616168
  6 months
    Still on treatment in NSR38%44%52%32%
      D/C for recurrence55%49%33%63%
      D/C for AEs3%3%8%4%
  12 months
    Still on treatment in NSR32%26%46%22%
      D/C for recurrence58%57%36%72%
      D/C for AEs7%11%8%6%
Study 2
Randomized135133129137
Achieved NSR103118100106
  6 months
    Still on treatment in NSR41%49%57%22%
      D/C for recurrence48%42%27%72%
      D/C for AEs9%6%10%4%
  12 months
    Still on treatment in NSR25%42%49%16%
      D/C for recurrence59%47%32%76%
      D/C for AEs11%6%12%5%

Table 3 and Figures 3 and 4 show, by randomized dose, the effectiveness of TIKOSYN in maintaining NSR using Kaplan Meier analysis, which shows patients remaining on treatment.

Table 3: P-Values and Median Time (days) to Recurrence of AF/AFl
TIKOSYN Dose
125 mcg BID250 mcg BID500 mcg BIDPlacebo
Median time to recurrence of AF/AFl could not be estimated accurately for the 250 mcg BID treatment group in Study 2 and the 500 mcg BID treatment groups in Studies 1 and 2 because TIKOSYN maintained >50% of patients (51%, 58% and 66%, respectively) in NSR for the 12 months duration of the studies.
Study 1
  p-value vs placeboP=0.21P=0.10P<0.001
  Median time to recurrence (days)31179>36527
Study 2
  p-value vs placeboP=0.006P<0.001P<0.001
  Median time to recurrence (days)182>365>36534
Figure 3: Maintenance of Normal Sinus Rhythm, TIKOSYN Regimen vs. Placebo (Study 1).

The point estimates of the probabilities of remaining in NSR at 6 and 12 months were 62% and 58% respectively for TIKOSYN 500 mcg BID, 50% and 37% for TIKOSYN 250 mcg BID, and 37% and 25% respectively on placebo.

Figure 4: Maintenance of Normal Sinus Rhythm, TIKOSYN Regimen vs. Placebo (Study 2).

The point estimates of the probabilities of remaining in NSR at 6 and 12 months were 71% and 66% respectively for TIKOSYN 500 mcg BID, 56% and 51% for TIKOSYN 250 mcg BID, and 26% and 21% respectively on placebo.

In both studies, TIKOSYN resulted in a dose-related increase in the number of patients maintained in NSR at all time periods and delayed the time of recurrence of sustained AF. Data pooled from both studies show that there is a positive relationship between the probability of staying in NSR, TIKOSYN dose, and increase in QTc (see Figure 2 in CLINICAL PHARMACOLOGY: Dose-Response and Concentration Response for QT Interval).

Analysis of pooled data for patients randomized to a TIKOSYN dose of 500 mcg twice daily showed that maintenance of NSR was similar in both males and females, in both patients aged <65 years and patients ≥65 years of age, and in both patients with atrial flutter as a primary diagnosis and those with a primary diagnosis of atrial fibrillation.

During the period of in-hospital initiation of dosing, 23% of patients in Studies 1 and 2 had their dose adjusted downward on the basis of their calculated creatinine clearance, and 3% had their dose down-titrated due to increased QT interval or QTc. Increased QT interval or QTc led to discontinuation of therapy in 3% of patients.

Safety in Patients with Structural Heart Disease: DIAMOND Studies (The Danish Investigations of Arrhythmia and Mortality on Dofetilide)

The two DIAMOND studies were 3-year trials comparing the effects of TIKOSYN and placebo on mortality and morbidity in patients with impaired left ventricular function (ejection fraction ≤35%). Patients were treated for at least one year. One study was in patients with moderate to severe (60% NYHA Class III or IV) congestive heart failure (DIAMOND CHF) and the other was in patients with recent myocardial infarction (DIAMOND MI) (of whom 40% had NYHA Class III or IV heart failure). Both groups were at relatively high risk of sudden death. The DIAMOND trials were intended to determine whether TIKOSYN could reduce that risk. The trials did not demonstrate a reduction in mortality; however, they provide reassurance that, when initiated carefully, in a hospital or equivalent setting, TIKOSYN did not increase mortality in patients with structural heart disease, an important finding because other antiarrhythmics [notably the Class IC antiarrhythmics studied in the Cardiac Arrhythmia Suppression Trial (CAST) and a pure Class III antiarrhythmic, d-sotalol (SWORD)] have increased mortality in post-infarction populations. The DIAMOND trials therefore provide evidence of a method of safe use of TIKOSYN in a population susceptible to ventricular arrhythmias. In addition, the subset of patients with AF in the DIAMOND trials provide further evidence of safety in a population of patients with structural heart disease accompanying the AF. Note, however, that this AF population was given a lower (250 mcg BID) dose (see DIAMOND Patients with Atrial Fibrillation).

In both DIAMOND studies, patients were randomized to 500 mcg BID of TIKOSYN, but this was reduced to 250 mcg BID if calculated creatinine clearance was 40–60 mL/min, if patients had AF, or if QT interval prolongation (>550 msec or >20% increase from baseline) occurred after dosing. Dose reductions for reduced calculated creatinine clearance occurred in 47% and 45% of DIAMOND CHF and MI patients. Dose reductions for increased QT interval or QTc occurred in 5% and 7% of DIAMOND CHF and MI patients, respectively. Increased QT interval or QTc (>550 msec or >20% increase from baseline) resulted in discontinuation of 1.8% of patients in DIAMOND CHF and 2.5% of patients in DIAMOND MI.

In the DIAMOND studies all patients were hospitalized for at least 3 days after treatment was initiated and monitored by telemetry. Patients with QTc greater than 460 msec, second or third degree AV block (unless with pacemaker), resting heart rate <50 bpm, or prior history of polymorphic ventricular tachycardia were excluded.

DIAMOND CHF studied 1518 patients hospitalized with severe CHF who had confirmed impaired left ventricular function (ejection fraction ≤35%). Patients received a median duration of therapy of greater than one year. There were 311 deaths from all causes in patients randomized to TIKOSYN (n=762) and 317 deaths in patients randomized to placebo (n=756). The probability of survival at one year was 73% (95% CI: 70%– 76%) in the TIKOSYN group and 72% (95% CI: 69%– 75%) in the placebo group. Similar results were seen for cardiac deaths and arrhythmic deaths. Torsade de pointes occurred in 25/762 patients (3.3%) receiving TIKOSYN. The majority of cases (76%) occurred within the first 3 days of dosing. In all, 437/762 (57%) of patients on TIKOSYN and 459/756 (61%) on placebo required hospitalization. Of these, 229/762 (30%) of patients on TIKOSYN and 290/756 (38%) on placebo required hospitalization because of worsening heart failure.

DIAMOND MI studied 1510 patients hospitalized with recent myocardial infarction (2–7 days) who had confirmed impaired left ventricular function (ejection fraction ≤35%). Patients received a median duration of therapy of greater than one year. There were 230 deaths in patients randomized to TIKOSYN (n=749) and 243 deaths in patients randomized to placebo (n=761). The probability of survival at one year was 79% (95% CI: 76%– 82%) in the TIKOSYN group and 77% (95% CI: 74%– 80%) in the placebo group. Cardiac and arrhythmic mortality showed a similar result. Torsade de pointes occurred in 7/749 patients (0.9%) receiving TIKOSYN. Of these, 4 cases occurred within the first 3 days of dosing and 3 cases occurred between Day 4 and the conclusion of the study. In all, 371/749 (50%) of patients on TIKOSYN and 419/761 (55%) on placebo required hospitalization. Of these, 200/749 (27%) of patients on TIKOSYN and 205/761 (27%) on placebo required hospitalization because of worsening heart failure.

DIAMOND Patients with Atrial Fibrillation (the DIAMOND AF subpopulation). There were 506 patients in the two DIAMOND studies who had atrial fibrillation (AF) at entry to the studies (249 randomized to TIKOSYN and 257 randomized to placebo). DIAMOND AF patients randomized to TIKOSYN received 250 mcg BID; 65% of these patients had impaired renal function, so that 250 mcg BID represents the dose they would have received in the AF trials, which would give drug exposure similar to a person with normal renal function given 500 mcg BID. In the DIAMOND AF subpopulation there were 111 deaths (45%) in the 249 patients in the TIKOSYN group and 116 deaths (45%) in the 257 patients in the placebo group. Hospital readmission rates for any reason were 125/249 or 50% on TIKOSYN and 156/257 or 61% for placebo. Of these, readmission rates for worsening heart failure were 73/249 or 29% on TIKOSYN and 102/257 or 40% for placebo.

Of the 506 patients in the DIAMOND studies who had atrial fibrillation or flutter at baseline, 12% of patients in the TIKOSYN group and 2% of patients in the placebo group had converted to normal sinus rhythm after one month. In those patients converted to normal sinus rhythm, 79% of the TIKOSYN group and 42% of the placebo group remained in normal sinus rhythm for one year.

In the DIAMOND studies, although torsade de pointes occurred more frequently in the TIKOSYN-treated patients (see ADVERSE REACTIONS), TIKOSYN, given with an initial 3-day hospitalization and with dose modified for reduced creatinine clearance and increased QT interval, was not associated with an excess risk of mortality in these populations with structural heart disease in the individual studies or in an analysis of the combined studies. The presence of atrial fibrillation did not affect outcome.

INDICATIONS AND USAGE

Maintenance of Normal Sinus Rhythm (Delay in AF/AFl Recurrence)

TIKOSYN is indicated for the maintenance of normal sinus rhythm (delay in time to recurrence of atrial fibrillation/atrial flutter [AF/AFl]) in patients with atrial fibrillation/atrial flutter of greater than one week duration who have been converted to normal sinus rhythm. Because TIKOSYN can cause life threatening ventricular arrhythmias, it should be reserved for patients in whom atrial fibrillation/atrial flutter is highly symptomatic.

In general, antiarrhythmic therapy for atrial fibrillation/atrial flutter aims to prolong the time in normal sinus rhythm. Recurrence is expected in some patients. (See CLINICAL STUDIES.)

Conversion of Atrial Fibrillation/Flutter

TIKOSYN is indicated for the conversion of atrial fibrillation and atrial flutter to normal sinus rhythm.

TIKOSYN has not been shown to be effective in patients with paroxysmal atrial fibrillation.

CONTRAINDICATIONS

TIKOSYN is contraindicated in patients with congenital or acquired long QT syndromes. TIKOSYN should not be used in patients with a baseline QT interval or QTc >440 msec (500 msec in patients with ventricular conduction abnormalities). TIKOSYN is also contraindicated in patients with severe renal impairment (calculated creatinine clearance <20 mL/min).

The concomitant use of verapamil or the cation transport system inhibitors cimetidine, trimethoprim (alone or in combination with sulfamethoxazole) or ketoconazole with TIKOSYN is contraindicated (see WARNINGS, PRECAUTIONS, Drug-Drug Interactions), as each of these drugs cause a substantial increase in dofetilide plasma concentrations. In addition, other known inhibitors of the renal cation transport system such as prochlorperazine and megestrol should not be used in patients on TIKOSYN.

The concomitant use of hydrochlorothiazide (alone or in combinations such as with triamterene) with TIKOSYN is contraindicated (see PRECAUTIONS, Drug-Drug Interactions) because this has been shown to significantly increase dofetilide plasma concentrations and QT interval prolongation.

TIKOSYN is also contraindicated in patients with a known hypersensitivity to the drug.

WARNINGS

Ventricular Arrhythmia

TIKOSYN (dofetilide) can cause serious ventricular arrhythmias, primarily torsade de pointes (TdP) type ventricular tachycardia, a polymorphic ventricular tachycardia associated with QT interval prolongation. QT interval prolongation is directly related to dofetilide plasma concentration. Factors such as reduced creatinine clearance or certain dofetilide drug interactions will increase dofetilide plasma concentration. The risk of TdP can be reduced by controlling the plasma concentration through adjustment of the initial dofetilide dose according to creatinine clearance and by monitoring the ECG for excessive increases in the QT interval.

Treatment with dofetilide must therefore be started only in patients placed for a minimum of three days in a facility that can provide electrocardiographic monitoring and in the presence of personnel trained in the management of serious ventricular arrhythmias. Calculation of the creatinine clearance for all patients must precede administration of the first dose of dofetilide. For detailed instructions regarding dose selection, seeDOSAGE AND ADMINISTRATION.

The risk of dofetilide induced ventricular arrhythmia was assessed in three ways in clinical studies:

  • by description of the QT interval and its relation to the dose and plasma concentration of dofetilide;
  • by observing the frequency of TdP in TIKOSYN treated patients according to dose;
  • by observing the overall mortality rate in patients with atrial fibrillation and in patients with structural heart disease.

Drug-Drug Interactions

(see CONTRAINDICATIONS)

Because there is a linear relationship between dofetilide plasma concentration and QTc, concomitant drugs that interfere with the metabolism or renal elimination of dofetilide may increase the risk of arrhythmia (torsade de pointes). TIKOSYN is metabolized to a small degree by the CYP3A4 isoenzyme of the cytochrome P450 system and an inhibitor of this system could increase systemic dofetilide exposure. More important, dofetilide is eliminated by cationic renal secretion, and three inhibitors of this process have been shown to increase systemic dofetilide exposure. The magnitude of the effect on renal elimination by cimetidine, trimethoprim and ketoconazole (all contraindicated concomitant uses with dofetilide) suggests that all renal cation transport inhibitors should be contraindicated.

Hypokalemia and Potassium-Depleting Diuretics

Hypokalemia or hypomagnesemia may occur with administration of potassium-depleting diuretics, increasing the potential for torsade de pointes. Potassium levels should be within the normal range prior to administration of TIKOSYN and maintained in the normal range during administration of TIKOSYN (see DOSAGE AND ADMINISTRATION).

Use with Drugs that Prolong QT Interval and Antiarrhythmic Agents

The use of TIKOSYN in conjunction with other drugs that prolong the QT interval has not been studied and is not recommended. Such drugs include phenothiazines, cisapride, bepridil, tricyclic antidepressants, certain oral macrolides, and certain fluoroquinolones. Class I or Class III antiarrhythmic agents should be withheld for at least three half-lives prior to dosing with TIKOSYN. In clinical trials, TIKOSYN was administered to patients previously treated with oral amiodarone only if serum amiodarone levels were below 0.3 mg/L or amiodarone had been withdrawn for at least three months.

PRECAUTIONS

Renal Impairment

The overall systemic clearance of dofetilide is decreased and plasma concentration increased with decreasing creatinine clearance. The dose of TIKOSYN must be adjusted based on creatinine clearance (see DOSAGE AND ADMINISTRATION). Patients undergoing dialysis were not included in clinical studies, and appropriate dosing recommendations for these patients are unknown. There is no information about the effectiveness of hemodialysis in removing dofetilide from plasma.

Hepatic Impairment

After adjustment for creatinine clearance, no additional dose adjustment is required for patients with mild or moderate hepatic impairment. Patients with severe hepatic impairment have not been studied. TIKOSYN should be used with particular caution in these patients.

Cardiac Conduction Disturbances

Animal and human studies have not shown any adverse effects of dofetilide on conduction velocity. No effect on AV nodal conduction following TIKOSYN treatment was noted in normal volunteers and in patients with 1st degree heart block. Patients with sick sinus syndrome or with 2nd or 3rd degree heart block were not included in the Phase 3 clinical trials unless a functioning pacemaker was present. TIKOSYN has been used safely in conjunction with pacemakers (53 patients in DIAMOND studies, 136 in trials in patients with ventricular and supraventricular arrhythmias).

Information For Patients

Please refer patient to the patient package insert.

Prior to initiation of TIKOSYN therapy, the patient should be advised to read the patient package insert and reread it each time therapy is renewed in case the patient's status has changed. The patient should be fully instructed on the need for compliance with the recommended dosing of TIKOSYN and the potential for drug interactions, and the need for periodic monitoring of QTc and renal function to minimize the risk of serious abnormal rhythms.

Drug/Laboratory Test Interactions

None known.

Drug-Drug Interactions

Potential Drug Interactions

Dofetilide is eliminated in the kidney by cationic secretion. Inhibitors of renal cationic secretion are contraindicated with TIKOSYN. In addition, drugs that are actively secreted via this route (e.g., triamterene, metformin and amiloride) should be co-administered with care as they might increase dofetilide levels.

Dofetilide is metabolized to a small extent by the CYP3A4 isoenzyme of the cytochrome P450 system. Inhibitors of the CYP3A4 isoenzyme could increase systemic dofetilide exposure. Inhibitors of this isoenzyme (e.g., macrolide antibiotics, azole antifungal agents, protease inhibitors, serotonin reuptake inhibitors, amiodarone, cannabinoids, diltiazem, grapefruit juice, nefazadone, norfloxacin, quinine, zafirlukast) should be cautiously coadministered with TIKOSYN as they can potentially increase dofetilide levels. Dofetilide is not an inhibitor of CYP3A4 nor of other cytochrome P450 isoenzymes (e.g., CYP2C9, CYP2D6) and is not expected to increase levels of drugs metabolized by CYP3A4.

Other Drug Interaction Information

Carcinogenesis, Mutagenesis, Impairment Of Fertility

Dofetilide had no genotoxic effects, with or without metabolic activation, based on the bacterial mutation assay and tests of cytogenetic aberrations in vivo in mouse bone marrow and in vitro in human lymphocytes. Rats and mice treated with dofetilide in the diet for two years showed no evidence of an increased incidence of tumors compared to controls. The highest dofetilide dose administered for 24 months was 10 mg/kg/day to rats and 20 mg/kg/day to mice. Mean dofetilide AUCs(0-24hr) at these doses were about 26 and 10 times, respectively, the maximum likely human AUC.

There was no effect on mating or fertility when dofetilide was administered to male and female rats at doses as high as 1.0 mg/kg/day, a dose that would be expected to provide a mean dofetilide AUC(0-24hr) about 3 times the maximum likely human AUC. Increased incidences of testicular atrophy and epididymal oligospermia and a reduction in testicular weight were, however, observed in other studies in rats. Reduced testicular weight and increased incidence of testicular atrophy were also consistent findings in dogs and mice. The no effect doses for these findings in chronic administration studies in these 3 species (3, 0.1 and 6 mg/kg/day) were associated with mean dofetilide AUCs that were about 4, 1.3 and 3 times the maximum likely human AUC, respectively.

Pregnancy Category C

Dofetilide has been shown to adversely affect in utero growth and survival of rats and mice when orally administered during organogenesis at doses of 2 or more mg/kg/day. Other than an increased incidence of non-ossified 5th metacarpal, and the occurrence of hydroureter and hydronephroses at doses as low as 1 mg/kg/day in the rat, structural anomalies associated with drug treatment were not observed in either species at doses below 2 mg/kg/day. The clearest drug-effect associations were for sternebral and vertebral anomalies in both species; cleft palate, adactyly, levocardia, dilation of cerebral ventricles, hydroureter, hydronephroses, and unossified metacarpal in the rat; and increased incidence of unossified calcaneum in the mouse. The "no observed adverse effect dose" in both species was 0.5 mg/kg/day. The mean dofetilide AUCs(0-24hr) at this dose in the rat and mouse are estimated to be about equal to the maximum likely human AUC and about half the likely human AUC, respectively. There are no adequate and well controlled studies in pregnant women. Therefore, dofetilide should only be administered to pregnant women where the benefit to the patient justifies the potential risk to the fetus.

Nursing Mothers

There is no information on the presence of dofetilide in breast milk. Patients should be advised not to breast feed an infant if they are taking TIKOSYN.

Geriatric Use

Of the total number of patients in clinical studies of TIKOSYN, 46% were 65 to 89 years old. No overall differences in safety, effect on QTc, or effectiveness were observed between elderly and younger patients. Because elderly patients are more likely to have decreased renal function with a reduced creatinine clearance, care must be taken in dose selection. (See DOSAGE AND ADMINISTRATION.)

Use in Women

Female patients constituted 32% of the patients in the placebo-controlled trials of TIKOSYN. As with other drugs that cause torsade de pointes, TIKOSYN was associated with a greater risk of torsade de pointes in female patients than in male patients. During the TIKOSYN clinical development program the risk of torsade de pointes in females was approximately 3 times the risk in males. Unlike torsade de pointes, the incidence of other ventricular arrhythmias was similar in female patients receiving TIKOSYN and patients receiving placebo. Although no study specifically investigated this risk, in post-hoc analyses, no increased mortality was observed in females on TIKOSYN compared to females on placebo.

Pediatric Use

The safety and effectiveness of TIKOSYN in children (<18 years old) has not been established.

ADVERSE REACTIONS

The TIKOSYN clinical program involved approximately 8,600 patients in 130 clinical studies of normal volunteers and patients with supraventricular and ventricular arrhythmias. TIKOSYN was administered to 5,194 patients, including two large, placebo-controlled mortality trials (DIAMOND CHF and DIAMOND MI) in which 1,511 patients received TIKOSYN for up to three years.

In the following section, adverse reaction data for cardiac arrhythmias and non-cardiac adverse reactions are presented separately for patients included in the supraventricular arrhythmia development program and for patients included in the DIAMOND CHF and MI mortality trials (see CLINICAL STUDIES: Safety in Patients with Structural Heart Disease - DIAMOND Studies, for a description of these trials).

In studies of patients with supraventricular arrhythmias a total of 1346 and 677 patients were exposed to TIKOSYN and placebo for 551 and 207 patient years, respectively. A total of 8.7% of patients in the dofetilide groups were discontinued from clinical trials due to adverse events compared to 8.0% in the placebo groups. The most frequent reason for discontinuation (>1%) was ventricular tachycardia (2.0% on dofetilide vs. 1.3% on placebo). The most frequent adverse events were headache, chest pain, and dizziness.

Serious Arrhythmias and Conduction Disturbances

Torsade de pointes is the only arrhythmia that showed a dose-response relationship to TIKOSYN treatment. It did not occur in placebo treated patients. The incidence of torsade de pointes in patients with supraventricular arrhythmias was 0.8% (11/1346) (see WARNINGS). The incidence of torsade de pointes in patients who were dosed according to the recommended dosing regimen (see DOSAGE AND ADMINISTRATION) was 0.8% (4/525). Table 6 shows the frequency by randomized dose of serious arrhythmias and conduction disturbances reported as adverse events in patients with supraventricular arrhythmias.

Table 6: Incidence of Serious Arrhythmias and Conduction Disturbances in Patients with Supraventricular Arrhythmias
TIKOSYN DosePlacebo
Arrhythmia event:<250 mcg BID
N=217
250 mcg
BID
N=388
>250–500 mcg
BID
N=703
>500 mcg BID
N=38
N=677
Ventricular arrhythmiasPatients with more than one arrhythmia are counted only once in this category.Ventricular arrhythmias and ventricular tachycardia include all cases of torsade de pointes.3.7%2.6%3.4%15.8%2.7%
  Ventricular fibrillation00.3%0.4%2.6%0.1%
  Ventricular tachycardia3.7%2.6%3.3%13.2%2.5%
    Torsade de pointes00.3%0.9%10.5%0
Various forms of block
  AV block0.9%1.5%0.4%00.3%
  Bundle branch block00.5%0.1%00.1%
  Heart block00.5%0.1%00.1%

In the DIAMOND trials a total of 1511 patients were exposed to TIKOSYN for 1757 patient years. The incidence of torsade de pointes was 3.3% in CHF patients and 0.9% in patients with a recent MI.

Table 7 shows the incidence of serious arrhythmias and conduction disturbances reported as adverse events in the DIAMOND subpopulation that had AF at entry to these trials.

Table 7: Incidence of Serious Arrhythmias and Conduction Disturbances in Patients with AF at Entry to the DIAMOND Studies
TIKOSYNPlacebo
N=249N=257
Ventricular arrhythmiasPatients with more than one arrhythmia are counted only once in this category.Ventricular arrhythmias and ventricular tachycardia include all cases of torsade de pointes.14.5%13.6%
  Ventricular fibrillation4.8%3.1%
  Ventricular tachycardia12.4%11.3%
    Torsade de pointes1.6%0
Various forms of block
  AV block0.8%2.7%
  (Left) bundle branch block00.4%
  Heart block1.2%0.8%

Other Adverse Reactions

Table 8 presents other adverse events reported with a frequency of >2% on TIKOSYN and reported numerically more frequently on TIKOSYN than on placebo in the studies of patients with supraventricular arrhythmias.

Table 8: Frequency of Adverse Events Occurring at >2% on TIKOSYN, and Numerically More Frequently on TIKOSYN than Placebo in Patients with Supraventricular Arrhythmias
TIKOSYNPlacebo
Adverse Event%%
      
headache119
chest pain107
dizziness86
respiratory tract infection75
dyspnea65
nausea54
flu syndrome42
insomnia43
accidental injury31
back pain32
procedure (medical/surgical/health service)32
diarrhea32
rash32
abdominal pain32

Adverse events reported at a rate >2% but no more frequently on TIKOSYN than on placebo were: angina pectoris, anxiety, arthralgia, asthenia, atrial fibrillation, complications (application, injection, incision, insertion, or device), hypertension, pain, palpitation, peripheral edema, supraventricular tachycardia, sweating, urinary tract infection, ventricular tachycardia.

The following adverse events have been reported with a frequency of ≤2% and numerically more frequently with TIKOSYN than placebo in patients with supraventricular arrhythmias: angioedema, bradycardia, cerebral ischemia, cerebrovascular accident, edema, facial paralysis, flaccid paralysis, heart arrest, increased cough, liver damage, migraine, myocardial infarct, paralysis, paresthesia, sudden death, and syncope.

The incidences of clinically significant laboratory test abnormalities in patients with supraventricular arrhythmias were similar for patients on TIKOSYN and those on placebo. No clinically relevant effects were noted in serum alkaline phosphatase, serum GGT, LDH, AST, ALT, total bilirubin, total protein, blood urea nitrogen, creatinine, serum electrolytes (calcium, chloride, glucose, magnesium, potassium, sodium) or creatine kinase. Similarly, no clinically relevant effects were observed in hematologic parameters.

In the DIAMOND population, adverse events other than those related to the post-infarction and heart failure patient population were generally similar to those seen in the supraventricular arrhythmia groups.

OVERDOSAGE

There is no known antidote to TIKOSYN; treatment of overdose should therefore be symptomatic and supportive. The most prominent manifestation of overdosage is likely to be excessive prolongation of the QT interval.

In cases of overdose cardiac monitoring should be initiated. Charcoal slurry may be given soon after overdosing but has been useful only when given within 15 minutes of TIKOSYN administration. Treatment of torsade de pointes or overdose may include administration of isoproterenol infusion, with or without cardiac pacing. Administration of intravenous magnesium sulfate may be effective in the management of torsade de pointes. Close medical monitoring and supervision should continue until the QT interval returns to normal levels.

Isoproterenol infusion into anesthetized dogs with cardiac pacing rapidly attenuates the dofetilide-induced prolongation of atrial and ventricular effective refractory periods in a dose-dependent manner. Magnesium sulfate, administered prophylactically either intravenously or orally in a dog model, was effective in the prevention of dofetilide-induced torsade de pointes ventricular tachycardia. Similarly, in man, intravenous magnesium sulfate may terminate torsade de pointes, irrespective of cause.

TIKOSYN overdose was rare in clinical studies; there were two reported cases of TIKOSYN overdose in the oral clinical program. One patient received very high multiples of the recommended dose (28 capsules), was treated with gastric aspiration 30 minutes later, and experienced no events. One patient inadvertently received two 500 mcg doses one hour apart and experienced ventricular fibrillation and cardiac arrest 2 hours after the second dose.

In the supraventricular arrhythmia population only 38 patients received doses greater than 500 mcg BID, all of whom received 750 mcg BID irrespective of creatinine clearance. In this very small patient population the incidence of torsade de pointes was 10.5% (4/38 patients), and the incidence of new ventricular fibrillation was 2.6% (1/38 patients).

DOSAGE AND ADMINISTRATION

  • Therapy with TIKOSYN must be initiated (and, if necessary, re-initiated) in a setting that provides continuous electrocardiographic (ECG) monitoring and in the presence of personnel trained in the management of serious ventricular arrhythmias. Patients should continue to be monitored in this way for a minimum of three days. Additionally, patients should not be discharged within 12 hours of electrical or pharmacological conversion to normal sinus rhythm.
  • The dose of TIKOSYN must be individualized according to calculated creatinine clearance and QTc. (QT interval should be used if the heart rate is <60 beats per minute. There are no data on use of TIKOSYN when the heart rate is <50 beats per minute.) The usual recommended dose of TIKOSYN is 500 mcg BID, as modified by the dosing algorithm described below. For consideration of a lower dose, see Special Considerations below.
  • Serum potassium should be maintained within the normal range before TIKOSYN treatment is initiated and should be maintained within the normal range while the patient remains on TIKOSYN therapy. (See WARNINGS, Hypokalemia and Potassium Depleting Diuretics) In clinical trials potassium levels were generally maintained above 3.6–4.0 mEq/L.
  • Patients with atrial fibrillation should be anticoagulated according to usual medical practice prior to electrical or pharmacological cardioversion. Anticoagulant therapy may be continued after cardioversion according to usual medical practice for the treatment of people with AF. Hypokalemia should be corrected before initiation of TIKOSYN therapy (see WARNINGS, Ventricular Arrhythmia).
  • Patients to be discharged on TIKOSYN therapy from an in-patient setting as described above must have an adequate supply of TIKOSYN, at the patient's individualized dose, to allow uninterrupted dosing until the patient receives the first outpatient supply.
  • TIKOSYN is distributed only to those hospitals and other appropriate institutions confirmed to have received applicable dosing and treatment initiation education programs. Inpatient and subsequent outpatient discharge and refill prescriptions are filled only upon confirmation that the prescribing physician has received applicable dosing and treatment initiation education programs. For this purpose, a ul for use by pharmacists is maintained containing hospitals and physicians who have received one of the education programs.

Instructions for Individualized Dose Initiation

Maintenance of TIKOSYN Therapy

Renal function and QTc should be re-evaluated every three months or as medically warranted. If QTc exceeds 500 milliseconds (550 msec in patients with ventricular conduction abnormalities), TIKOSYN therapy should be discontinued and patients should be carefully monitored until QTc returns to baseline levels. If renal function deteriorates, adjust dose as described in Initiation of TIKOSYN Therapy, Step 3.

Special Considerations

Switch to TIKOSYN from Class I or other Class III Antiarrhythmic Therapy

Before initiating TIKOSYN therapy, previous antiarrhythmic therapy should be withdrawn under careful monitoring for a minimum of three (3) plasma half-lives. Because of the unpredictable pharmacokinetics of amiodarone, TIKOSYN should not be initiated following amiodarone therapy until amiodarone plasma levels are below 0.3 mcg/mL or until amiodarone has been withdrawn for at least three months.

Stopping TIKOSYN Prior to Administration of Potentially Interacting Drugs

If TIKOSYN needs to be discontinued to allow dosing of other potentially interacting drug(s), a washout period of at least two days should be followed before starting the other drug(s).

HOW SUPPLIED

TIKOSYN® 125 mcg (0.125 mg) capsules are supplied as No. 4 capsules with a light orange cap and white body, printed with TKN 125 PFIZER, and are available in:

TIKOSYN® 250 mcg (0.25 mg) capsules are supplied as No. 4 capsules, peach cap and body, printed with TKN 250 PFIZER, and are available in:

TIKOSYN® 500 mcg (0.5 mg) capsules are supplied as No. 2 capsules, peach cap and white body, printed with TKN 500 PFIZER, and are available in:

125 mcg (0.125 mg)250 mcg (0.25 mg)500 mcg (0.5 mg)
ObverseTKN 125TKN 250TKN 500
ReversePFIZERPFIZERPFIZER
Bottle of 140069-5800-610069-5810-610069-5820-61
Bottle of 600069-5800-600069-5810-600069-5820-60
Unit dose / 400069-5800-430069-5810-430069-5820-43

Store at controlled room temperature, 15° to 30°C (59° to 86°F).

PROTECT FROM MOISTURE AND HUMIDITY.

Dispense in tight containers (USP).

Rx only

LAB-0067-5.0

November 2006

PATIENT INFORMATION ABOUT TIKOSYN® (Tee' ko sin) (generic name: dofetilide)

This leaflet includes information about Tikosyn® that is important for you to know. Read this information carefully before you start taking Tikosyn. Also read it each time you get a refill of Tikosyn to see whether any information regarding your condition has changed. Talk with your doctor or pharmacist if you have any questions. The information in this leaflet cannot take the place of discussions with your health care provider.

What is the most important information I should know about Tikosyn?

Because you have irregular heartbeats (atrial fibrillation) that are troublesome to you, Tikosyn has been prescribed to help your heart to beat in a more normal way. However, in some patients Tikosyn can cause a different type of abnormal heartbeat, that can be dangerous, and in rare instances can even cause death. You may feel this different type of abnormal heartbeat as a fast beating of the heart with lightheadedness and fainting. The possibility of this different type of abnormal heartbeat is the reason you and your doctor have discussed whether your symptoms are troublesome enough for you to start taking Tikosyn.

Clinical studies using Tikosyn have shown that the most important way to decrease your chance of getting this different type of dangerous abnormal heartbeat is for you to take the dose of Tikosyn that is right for you. If this abnormal heartbeat occurs, it usually happens during the first few days of treatment. This is why you should be started on Tikosyn in a hospital or another place where your heartbeat can be watched closely by health care professionals for the first few days. They can help you if problems occur. When Tikosyn is started this way, this different type of abnormal heartbeat is rare and the hospital staff are there to treat it.

It is important that when you go home, you take the exact dose the doctor prescribed for you. At any time while you are taking Tikosyn, watch for signs that you may be getting this different type of abnormal heartbeat and call your doctor if they occur.

Call your doctor right away if you:

  • faint,
  • become dizzy, or
  • have fast heartbeats.

If you cannot reach your doctor, go to the nearest hospital emergency room. Take your Tikosyn capsules with you and show them to the doctor or nurse.

Also, call your doctor right away if you have any of the following conditions:

  • severe diarrhea,
  • unusual sweating,
  • vomiting,
  • less appetite than normal, or
  • more thirst than normal.

These are conditions that will make you more likely to get the different type of abnormal heartbeat.

If you take Tikosyn with certain other medicines, you will increase your chance of getting this different type of abnormal heartbeat. These medicines are uled below under "Who should not take Tikosyn?".

Once your doctor finds the right dose for you, always take that exact amount of Tikosyn. Never take an extra dose and never skip a dose of Tikosyn.

What is Tikosyn?

Tikosyn is a medicine that is given to patients with atrial fibrillation (irregular heartbeats). Atrial fibrillation happens when certain parts of the heart (the chambers known as atria) beat too fast or irregularly. When this happens, your heart cannot pump blood through your body as well as it should. This may make you feel weak and tired, or get out of breath easily. You may get an uncomfortable feeling in your chest and "fluttering" or "palpitations". Atrial fibrillation can be changed back (converted) to normal heart rhythm by an electric shock or by using certain medicines. However, atrial fibrillation can return. Tikosyn may help your heart to beat more regularly and stay beating regularly for a longer period of time.

Who should not take Tikosyn?

Tikosyn is not for everyone with irregular heartbeats (atrial fibrillation). This is why you and your doctor need to discuss the benefits and risks of Tikosyn and whether your symptoms are troublesome enough for you to start taking Tikosyn.

Do not take Tikosyn if you:

  • are taking certain other medicines, including
    • cimetidine (TAGAMET, TAGAMET HB)Listed trademarks are the property of their respective owners., used to treat heartburn, upset stomach, and stomach ulcers, available both by prescription and without a prescription
    • verapamil (CALAN, CALAN SR, COVERA-HS, ISOPTIN, ISOPTIN SR, VERELAN, VERELAN PM), used to treat high blood pressure and certain heart problems
    • ketoconazole (NIZORAL), used to treat certain fungus infections
    • trimethoprim alone (PROLOPRIM, TRIMPEX) or the combination of trimethoprim and sulfamethoxazole (BACTRIM, SEPTRA), used to treat certain bacterial infections
    • prochlorperazine (COMPAZINE), used to treat nausea and vomiting
    • megestrol (MEGACE), used to treat certain types of cancer or loss of appetite and weight loss associated with AIDS
    • hydrochlorothiazide alone or in combination with other medicines (such as ESIDRIX, EZIDE, HYDRODIURIL, HYDRO-PAR, MICROZIDE, or ORETIC)
  • have serious kidney problems or are on kidney dialysis.

Taking certain other medicines with Tikosyn can increase the chance that you will get the dangerous abnormal heartbeat discussed in "What is the most important information I should know about Tikosyn?". These include medicines used to treat heart conditions, high blood pressure, depression and other mental problems, asthma, allergies, hay fever, skin problems and infections. Therefore, you should be sure to tell your health care provider about all prescription and non-prescription medicines you are taking, as well as vitamins, dietary supplements, and any natural or herbal remedies.

In addition, tell your doctor about any problems you have with your heart, kidneys or liver.

If you are pregnant, you should know there is no information about the safety of Tikosyn in pregnant women or whether Tikosyn is passed into breast milk. Women who are taking Tikosyn should not breast feed a child.

Tikosyn is not recommended for children.

How should I take Tikosyn?

Your doctor will start you on Tikosyn in the hospital and will check your heart rhythm for the first 3 days of treatment. This will allow your doctor to find the right dose for you. Always take the exact amount your doctor prescribes. Never change your Tikosyn dose unless your doctor tells you to. Your doctor will do regular tests to check that the amount youre taking is still right for you.

Keep taking your Tikosyn until your doctor tells you to stop. Keep taking it even if you feel fine. However, never take an extra dose of Tikosyn, even if you do not feel well.

You may take Tikosyn with or without food. However, it is important to take Tikosyn at the same time every day. This gives your heart a steady supply of the medicine. It might be helpful to take Tikosyn at the same time as something you regularly do every day.

Never try to make up for a missed dose of Tikosyn. You could increase your chance of getting the different type of abnormal heartbeat. If you miss taking a dose of Tikosyn, just take your normal amount at the next scheduled time.

If you take more Tikosyn than you should have, call your doctor right away. If you cannot reach your doctor, go to the nearest hospital emergency room. Take your Tikosyn capsules with you to show to the doctor or nurse.

What should I avoid while taking Tikosyn?

Certain other medicines can increase the amount of Tikosyn in your body (see "Who should not take Tikosyn?"). This can increase your chance of getting the different type of abnormal heartbeat. Do not take Tikosyn with these medicines. Before you start taking Tikosyn tell your doctor about all prescription and non-prescription medicines you are taking (see also "Who should not take Tikosyn?"). Once you begin taking Tikosyn, do not start taking any new medicines until you check with your doctor.

Carry a ul of all the medicines and supplements you take. If you have to go to the hospital or are treated by new or different health care providers, tell them you are taking Tikosyn and show them the ul of other medicines you take. They need this information to make sure your medicines are safe to take at the same time.

What are the possible side effects of Tikosyn?

Tikosyn's most serious side effect, a different type of dangerous abnormal heartbeat, is discussed in "What is the most important information I should know about Tikosyn?". Dangerous abnormal heartbeats happen rarely. But they can be serious and, in rare instances, can even cause death.

Tikosyn's most common side effects are headache, chest pain, and dizziness. Tikosyn can also cause other side effects. If you are concerned about these or any other side effects, ask your doctor.

Important points about Tikosyn

Tikosyn can help you best if you take it as your doctor has prescribed it.

  • Take your medicine every day as prescribed
  • Do not miss doses or take extra doses
  • Call your doctor right away if you feel new fast heartbeats with lightheadedness and fainting. These can be serious and in rare instances can even cause death.
  • Tell your doctor and pharmacist the names of all medications (prescription, non-prescription, and natural/herbal remedies) you are taking
  • Do not start taking any other medicines without telling your doctor
  • Do not take cimetidine (TAGAMET, TAGAMET HB) or verapamil (CALAN, CALAN SR, COVERA-HS, ISOPTIN, ISOPTIN SR or VERELAN, VERELAN PM) or ketoconazole (NIZORAL), trimethoprim alone (PROLOPRIM, TRIMPEX) or in combination with sulfamethoxazole (BACTRIM, SEPTRA), prochlorperazine (COMPAZINE) or megestrol (MEGACE) , or hydrochlorothiazide alone or in combination with other medicines (such as ESIDRIX, EZIDE, HYDRODIURIL, HYDRO-PAR, MICROZIDE, or ORETIC)
  • Go for all your regular checkups
  • Get your refills on time
  • Do not stop taking Tikosyn until your doctor tells you to stop.

This leaflet provides a summary of information about Tikosyn. Your doctor or pharmacist has a longer leaflet written for healthcare professionals that you can ask to read. Tikosyn was prescribed for your particular condition. Do not use it for another condition or give it to others.

LAB-0068-5.0

November 2006