RYTHMOL

GlaxoSmithKline LLC

HIGHLIGHTS OF PRESCRIBING INFORMATIONThese highlights do not include all the information needed to use RYTHMOL safely and effectively. See full prescribing information for RYTHMOL. RYTHMOL (propafenone hydrochloride) Tablets for oral useInitial U.S. Approval: 1989BOXED WARNINGWARNING: MORTALITY See full prescribing information for complete boxed warning. • An increased rate of death or reversed cardiac arrest rate was seen in subjects treated with encainide or flecainide (Class IC antiarrhythmics) compared with that seen in subjects assigned to placebo. At present it is prudent to consider any IC antiarrhythmic to have a significant risk of provoking proarrhythmic events in patients with structural heart disease. • Given the lack of any evidence that these drugs improve survival, antiarrhythmic agents should generally be avoided in patients with non-life-threatening ventricular arrhythmias, even if the patients are experiencing unpleasant, but not life-threatening, symptoms or signs. INDICATIONS AND USAGERYTHMOL is an antiarrhythmic indicated to: •prolong the time to recurrence of symptomatic atrial fibrillation (AF) in patients with episodic (most likely paroxysmal or persistent) AF who do not have structural heart disease. (1) •prolong the time to recurrence of paroxysmal supraventricular tachycardia (PSVT) associated with disabling symptoms in patients who do not have structural heart disease. (1) •treat documented life-threatening ventricular arrhythmias. (1) Usage Considerations: •Use in patients with permanent atrial fibrillation or with atrial flutter or PSVT has not been evaluated. Do not use to control ventricular rate during atrial fibrillation. (1) •In patients with atrial fibrillation and atrial flutter, use RYTHMOL with drugs that increase the atrioventricular nodal refractory period. (1) •Because of proarrhythmic effects, use with lesser ventricular arrhythmias is not recommended, even if patients are symptomatic. (1) •The effect of propafenone on mortality has not been determined. (1) DOSAGE AND ADMINISTRATION •Initiate therapy with 150 mg given every 8 hours. (2) •As needed, uptitrate in 3 to 4 days to 225 to 300 mg every 8 hours. (2) •Consider reducing the dose in patients with hepatic impairment, significant widening of the QRS complex, or second- or third-degree AV block. (2) DOSAGE FORMS AND STRENGTHSTablets: 150 mg, 225 mg. (3)CONTRAINDICATIONS •Heart failure, cardiogenic shock, or marked hypotension (4) •Sinoatrial, atrioventricular, and intraventricular disorders of impulse generation or conduction in the absence of pacemaker (4) •Known Brugada Syndrome (4) •Bradycardia (4) •Bronchospastic disorders and severe obstructive pulmonary disease (4) •Marked electrolyte imbalance (4) WARNINGS AND PRECAUTIONS •May cause new or worsened arrhythmias. Evaluate patients via ECG prior to and during therapy. (5.1) •RYTHMOL may unmask Brugada or Brugada-like Syndrome. (4, 5.2) •Avoid use with other drugs that prolong the QT interval. (5.3) •Avoid simultaneous use of propafenone with both a cytochrome P450 2D6 inhibitor and a 3A4 inhibitor. (5.4) •May provoke overt heart failure. (5.5) •May cause dose-related first-degree AV block or other conduction disturbances. Only use in patients with conduction disorders who have pacemakers. (5.6) •May affect artificial pacemakers.Monitor pacemaker function. (5.7) •Agranulocytosis: Patients should report signs of infection. (5.8) •May exacerbate myasthenia gravis. (5.11) Side EffectsThe most commonly reported adverse events with propafenone (>5%) included: unusual taste, nausea and/or vomiting, dizziness, constipation, headache, fatigue, first-degree AV block, and intraventricular conduction delay. (6.1) To report SUSPECTED ADVERSE REACTIONS, contact GlaxoSmithKline at 1-888-825-5249 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. DRUG INTERACTIONS •Inhibitors of CYP2D6, 1A2, and 3A4 increase propafenone exposure. (7.1) •Propafenone may increase digoxin or warfarin levels. (7.2, 7.3) •Orlistat may reduce propafenone exposure. Taper orlistat withdrawal. (7.4) •Lidocaine may increase central nervous system side effects. (7.6)

FULL PRESCRIBING INFORMATION: CONTENTS*

• WARNING: MORTALITY
• 1 RYTHMOL INDICATIONS AND USAGE
• 2 RYTHMOL DOSAGE AND ADMINISTRATION
• 3 DOSAGE FORMS AND STRENGTHS
• 4 RYTHMOL CONTRAINDICATIONS
• 5 WARNINGS AND PRECAUTIONS
  • 5.1 Proarrhythmic Effects
  • 5.3 Use With Drugs That Prolong the QT Interval and Antiarrhythmic Agents
  • 5.4 Drug Interactions: Simultaneous Use With Inhibitors of Cytochrome P450 Isoenzymes 2D6 and 3A4
  • 5.5 Use in Patients With a History of Heart Failure
  • 5.6 Conduction Disturbances
  • 5.7 Effects on Pacemaker Threshold
  • 5.8 Agranulocytosis
  • 5.9 Use in Patients With Hepatic Dysfunction
  • 5.10 Use in Patients With Renal Dysfunction
  • 5.11 Use in Patients With Myasthenia Gravis
  • 5.12 Elevated ANA Titers
  • 5.13 Impaired Spermatogenesis
• 6 RYTHMOL ADVERSE REACTIONS
  • 6.1 Clinical Trials Experience
  • 6.2 Postmarketing Experience
• 7 DRUG INTERACTIONS
  • 7.1 CYP2D6 and CYP3A4 Inhibitors
  • 7.2 Digoxin
  • 7.3 Warfarin
  • 7.4 Orlistat
  • 7.5 Beta-Antagonists
  • 7.6 Lidocaine
• 8 USE IN SPECIFIC POPULATIONS
  • 8.1 Pregnancy
  • 8.2 Labor and Delivery
  • 8.3 Nursing Mothers
  • 8.4 Pediatric Use
  • 8.5 Geriatric Use
• 10 OVERDOSAGE
• 11 RYTHMOL DESCRIPTION
• 12 CLINICAL PHARMACOLOGY
  • 12.1 Mechanism of Action
  • 12.2 Pharmacodynamics
  • 12.3 Pharmacokinetics
• 13 NONCLINICAL TOXICOLOGY
  • 13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility
  • 13.2 Animal Toxicology and/or Pharmacology
• 14 CLINICAL STUDIES
• 16 HOW SUPPLIED/STORAGE AND HANDLING
• 17 PATIENT COUNSELING INFORMATION
  • 17.1 Information for Patients

FULL PRESCRIBING INFORMATION

1 INDICATIONS AND USAGE

RYTHMOL^® is indicated to:

• •prolong the time to recurrence of paroxysmal atrial fibrillation/flutter (PAF) associated with disabling symptoms in patients without structural heart disease.
• •prolong the time to recurrence of paroxysmal supraventricular tachycardia (PSVT) associated with disabling symptoms in patients without structural heart disease.
• •treat documented ventricular arrhythmias, such as sustained ventricular tachycardia that, in the judgment of the physician, are life-threatening. Initiate treatment in the hospital.

Usage Considerations:

• •The use of RYTHMOL in patients with permanent atrial fibrillation (AF) or in patients exclusively with atrial flutter or PSVT has not been evaluated. Do not use RYTHMOL to control ventricular rate during AF.
• •Some patients with atrial flutter treated with propafenone have developed 1:1 conduction, producing an increase in ventricular rate. Concomitant treatment with drugs that increase the functional atrioventricular (AV) nodal refractory period is recommended.
• •The use of RYTHMOL in patients with chronic atrial fibrillation has not been evaluated.
• •Because of the proarrhythmic effects of RYTHMOL, its use with lesser ventricular arrhythmias is not recommended, even if patients are symptomatic, and any use of the drug should be reserved for patients in whom, in the opinion of the physician, the potential benefits outweigh the risks.
• •The effect of propafenone on mortality has not been determined [see Boxed Warning].

2 DOSAGE AND ADMINISTRATION

The dose of RYTHMOL must be individually titrated on the basis of response and tolerance. Initiate therapy with RYTHMOL 150 mg given every 8 hours (450 mg/day). Dosage may be increased at a minimum of 3 to 4 day intervals to 225 mg every 8 hours (675 mg/day). If additional therapeutic effect is needed, the dose of RYTHMOL may be increased to 300 mg every 8 hours (900 mg/day). The usefulness and safety of dosages exceeding 900 mg per day have not been established.

In patients with hepatic impairment or those with significant widening of the QRS complex or second- or third-degree AV block, consider reducing the dose.

As with other antiarrhythmic agents, in the elderly or in ventricular arrhythmia patients with marked previous myocardial damage, the dose of RYTHMOL should be increased more gradually during the initial phase of treatment.

The combination of CYP3A4 inhibition and either CYP2D6 deficiency or CYP2D6 inhibition with the simultaneous administration of propafenone may significantly increase the concentration of propafenone and thereby increase the risk of proarrhythmia and other adverse events. Therefore, avoid simultaneous use of RYTHMOL with both a CYP2D6 inhibitor and a CYP3A4 inhibitor [see Warnings and Precautions (5.4), Drug Interactions (7.1)].

3 DOSAGE FORMS AND STRENGTHS

150-mg and 225-mg scored, round, film-coated tablets.

4 CONTRAINDICATIONS

RYTHMOL is contraindicated in the following circumstances:

• •Heart failure
• •Cardiogenic shock
• •Sinoatrial, atrioventricular, and intraventricular disorders of impulse generation or conduction (e.g., sick sinus node syndrome, AV block) in the absence of an artificial pacemaker
• • Known Brugada Syndrome
• •Bradycardia
• •Marked hypotension
• •Bronchospastic disorders or severe obstructive pulmonary disease
• •Marked electrolyte imbalance

5 WARNINGS AND PRECAUTIONS

5.1 Proarrhythmic Effects

Propafenone has caused new or worsened arrhythmias. Such proarrhythmic effects include sudden death and life-threatening ventricular arrhythmias such as ventricular fibrillation, ventricular tachycardia, asystole, and torsade de pointes. It may also worsen premature ventricular contractions or supraventricular arrhythmias, and it may prolong the QT interval. It is therefore essential that each patient given RYTHMOL be evaluated electrocardiographically prior to and during therapy to determine whether the response to RYTHMOL supports continued treatment. Because propafenone prolongs the QRS interval in the electrocardiogram, changes in the QT interval are difficult to interpret [see Clinical Pharmacology (12.2)].

In a US uncontrolled, open-label, multicenter trial in subjects with symptomatic supraventricular tachycardia (SVT), 1.9% (9/474) of these subjects experienced ventricular tachycardia (VT) or ventricular fibrillation (VF) during the trial. However, in 4 of the 9 subjects, the ventricular tachycardia was of atrial origin. Six of the 9 subjects that developed ventricular arrhythmias did so within 14 days of onset of therapy. About 2.3% (11/474) of all subjects had a recurrence of SVT during the trial which could have been a change in the subjects’ arrhythmia behavior or could represent a proarrhythmic event. Case reports in patients treated with propafenone for atrial fibrillation/flutter have included increased premature ventricular contractions (PVCs), VT, VF, torsade de pointes, asystole, and death.

Overall in clinical trials with RYTHMOL (which included subjects treated for ventricular arrhythmias, atrial fibrillation/flutter, and PSVT), 4.7% of all subjects had new or worsened ventricular arrhythmia possibly representing a proarrhythmic event (0.7% was an increase in PVCs; 4.0% a worsening, or new appearance, of VT or VF). Of the subjects who had worsening of VT (4%), 92% had a history of VT and/or VT/VF, 71% had coronary artery disease, and 68% had a prior myocardial infarction. The incidence of proarrhythmia in subjects with less serious or benign arrhythmias, which include subjects with an increase in frequency of PVCs, was 1.6%. Although most proarrhythmic events occurred during the first week of therapy, late events also were seen and the CAST trial [see Boxed Warning: Mortality] suggests that an increased risk of proarrythmia is present throughout treatment.

In a trial of sustained-release propafenone (RYTHMOL SR^®), there were too few deaths to assess the long-term risk to patients. There were 5 deaths, 3 in the pooled group for RYTHMOL SR (0.8%) and 2 in the placebo group (1.6%). In the overall database of 8 trials of RYTHMOL SR and immediate-release RYTHMOL, the mortality rate was 2.5% per year on propafenone and 4.0% per year on placebo. Concurrent use of propafenone with other antiarrhythmic agents has not been well studied.

Brugada Syndrome may be unmasked after exposure to RYTHMOL. Perform an ECG after initiation of RYTHMOL, and discontinue the drug if changes are suggestive of Brugada Syndrome [see Contraindications (4)].

5.3 Use With Drugs That Prolong the QT Interval and Antiarrhythmic Agents

The use of RYTHMOL in conjunction with other drugs that prolong the QT interval has not been extensively studied. Such drugs may include many antiarrhythmics, some phenothiazines, tricyclic antidepressants, and oral macrolides. Withhold Class IA and III antiarrhythmic agents for at least 5 half-lives prior to dosing with RYTHMOL. Avoid the use of propafenone with Class IA and III antiarrhythmic agents (including quinidine and amiodarone). There is only limited experience with the concomitant use of Class IB or IC antiarrhythmics.

5.4 Drug Interactions: Simultaneous Use With Inhibitors of Cytochrome P450 Isoenzymes 2D6 and 3A4

Propafenone is metabolized by CYP2D6, CYP3A4, and CYP1A2 isoenzymes. Approximately 6% of Caucasians in the US population are naturally deficient in CYP2D6 activity and to a somewhat lesser extent in other demographic groups. Drugs that inhibit these CYP pathways (such as desipramine, paroxetine, ritonavir, sertraline for CYP2D6; ketoconazole, erythromycin, saquinavir, and grapefruit juice for CYP3A4; and amiodarone and tobacco smoke for CYP1A2) can be expected to cause increased plasma levels of propafenone.

Increased exposure to propafenone may lead to cardiac arrhythmias and exaggerated beta-adrenergic blocking activity. Because of its metabolism, the combination of CYP3A4 inhibition and either CYP2D6 deficiency or CYP2D6 inhibition in users of propafenone is potentially hazardous. Therefore, avoid simultaneous use of RYTHMOL with both a CYP2D6 inhibitor and a CYP3A4 inhibitor.

5.5 Use in Patients With a History of Heart Failure

Propafenone exerts a negative inotropic activity on the myocardium as well as beta-blockade effects and may provoke overt heart failure.

In clinical trial experience with RYTHMOL, new or worsened congestive heart failure (CHF) has been reported in 3.7% of subjects with ventricular arrhythmia; of those 0.9% were considered probably or definitely related to propafenone HCl. Of the subjects with CHF probably related to propafenone, 80% had pre-existing heart failure and 85% had coronary artery disease. CHF attributable to propafenone HCl developed rarely (<0.2%) in ventricular arrhythmia subjects who had no previous history of CHF. CHF occurred in 1.9% of subjects studied with PAF or PSVT.

In a US trial of RYTHMOL SR in subjects with symptomatic AF, heart failure was reported in 4 (1.0%) subjects receiving RYTHMOL SR (all doses), compared with 1 (0.8%) subject receiving placebo.

5.6 Conduction Disturbances

Propafenone slows atrioventricular conduction and may also cause dose-related first-degree AV block. Average PR interval prolongation and increases in QRS duration are also dose-related. Do not give propafenone to patients with atrioventricular and intraventricular conduction defects in the absence of a pacemaker [see Contraindications (4), Clinical Pharmacology (12.2)].

The incidence of first-degree, second-degree, and third-degree AV block observed in 2,127 subjects with ventricular arrhythmia was 2.5%, 0.6%, and 0.2%, respectively. Development of second- or third-degree AV block requires a reduction in dosage or discontinuation of propafenone HCl. Bundle branch block (1.2%) and intraventricular conduction delay (1.1%) have been reported in subjects receiving propafenone. Bradycardia has also been reported (1.5%). Experience in patients with sick sinus node syndrome is limited and these patients should not be treated with propafenone.

In a US trial in 523 subjects with a history of symptomatic AF treated with RYTHMOL SR, sinus bradycardia (rate <50 beats/min) was reported with the same frequency with RYTHMOL SR and placebo.

5.7 Effects on Pacemaker Threshold

Propafenone may alter both pacing and sensing thresholds of implanted pacemakers and defibrillators. During and after therapy, monitor and re-program these devices accordingly.

5.8 Agranulocytosis

Agranulocytosis has been reported in patients receiving propafenone. Generally, the agranulocytosis occurred within the first 2 months of propafenone therapy and upon discontinuation of therapy; the white count usually normalized by 14 days. Unexplained fever or decrease in white cell count, particularly during the initial 3 months of therapy, warrant consideration of possible agranulocytosis or granulocytopenia. Instruct patients to report promptly any signs of infection such as fever, sore throat, or chills.

5.9 Use in Patients With Hepatic Dysfunction

Propafenone is highly metabolized by the liver. Severe liver dysfunction increases the bioavailability of propafenone to approximately 70% compared with 3% to 40% in patients with normal liver function. In 8 subjects with moderate to severe liver disease, the mean half-life was approximately 9 hours. Increased bioavailability of propafenone in these patients may result in excessive accumulation. Carefully monitor patients with impaired hepatic function for excessive pharmacological effects [see Overdosage (10)].

5.10 Use in Patients With Renal Dysfunction

Approximately 50% of propafenone metabolites are excreted in the urine following administration of RYTHMOL.

In patients with impaired renal function, monitor for signs of overdosage [see Overdosage (10)].

5.11 Use in Patients With Myasthenia Gravis

Exacerbation of myasthenia gravis has been reported during propafenone therapy.

5.12 Elevated ANA Titers

Positive ANA titers have been reported in patients receiving propafenone. They have been reversible upon cessation of treatment and may disappear even in the face of continued propafenone therapy. These laboratory findings were usually not associated with clinical symptoms, but there is one published case of drug-induced lupus erythematosis (positive rechallenge); it resolved completely upon discontinuation of therapy. Carefully evaluate patients who develop an abnormal ANA test and, if persistent or worsening elevation of ANA titers is detected, consider discontinuing therapy.

5.13 Impaired Spermatogenesis

Reversible disorders of spermatogenesis have been demonstrated in monkeys, dogs, and rabbits after high-dose intravenous administration of propafenone. Evaluation of the effects of short-term administration of RYTHMOL on spermatogenesis in 11 normal subjects suggested that propafenone produced a reversible, short-term drop (within normal range) in sperm count.

6 ADVERSE REACTIONS

6.1 Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Adverse reactions associated with RYTHMOL occur most frequently in the gastrointestinal, cardiovascular, and central nervous systems. About 20% of subjects treated with RYTHMOL have discontinued treatment because of adverse reactions.

Adverse reactions reported for > 1.5% of 474 subjects with SVT who received RYTHMOL in US clinical trials are presented in Table 1 by incidence and percent discontinuation, reported to the nearest percent.

In controlled trials in subjects with ventricular arrhythmia, the most common reactions reported for RYTHMOL and more frequent than on placebo were unusual taste, dizziness, first degree AV block, intraventricular conduction delay, nausea and/or vomiting, and constipation. Headache was relatively common also, but was not increased compared with placebo. Other reactions reported more frequently than on placebo or comparator and not already reported elsewhere included anxiety, angina, second-degree AV block, bundle branch block, loss of balance, congestive heart failure, and dyspepsia.

Adverse reactions reported for ≥1% of 2,127 subjects with ventricular arrhythmia who received propafenone in US clinical trials were evaluated by daily dose. The most common adverse reactions appeared dose-related (but note that most subjects spent more time at the larger doses), especially dizziness, nausea and/or vomiting, unusual taste, constipation, and blurred vision. Some less common reactions may also have been dose-related such as first-degree AV block, congestive heart failure, dyspepsia, and weakness. Other adverse reactions included rash, syncope, chest pain, abdominal pain, ataxia, and hypotension.

In addition, the following adverse reactions were reported less frequently than 1% either in clinical trials or in marketing experience. Causality and relationship to propafenone therapy cannot necessarily be judged from these events.

Cardiovascular System: Atrial flutter, AV dissociation, cardiac arrest, flushing, hot flashes, sick sinus syndrome, sinus pause or arrest, supraventricular tachycardia.

Nervous System: Abnormal dreams, abnormal speech, abnormal vision, confusion, depression, memory loss, numbness, paresthesias, psychosis/mania, seizures (0.3%), tinnitus, unusual smell sensation, vertigo.

Gastrointestinal: Cholestasis , elevated liver enzymes (alkaline phosphatase, serum transaminases), gastroenteritis, hepatitis .

Hematologic: Agranulocytosis, anemia, bruising, granulocytopenia, leukopenia, purpura, thrombocytopenia.

Other: Alopecia, eye irritation, impotence, increased glucose, positive ANA (0.7%), muscle cramps, muscle weakness, nephrotic syndrome, pain, pruritus.

6.2 Postmarketing Experience

The following adverse reactions have been identified during post-approval use of RYTHMOL. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Gastrointestinal: A number of patients with liver abnormalities associated with propafenone therapy have been reported in postmarketing experience. Some appeared due to hepatocellular injury, some were cholestatic, and some showed a mixed picture. Some of these reports were simply discovered through clinical chemistries, others because of clinical symptoms including fulminant hepatitis and death. One case was rechallenged with a positive outcome.

Blood and Lymphatic System: Increased bleeding time.

Immune System: Lupus erythematosis.

Nervous System: Apnea, coma.

Renal and Urinary: Hyponatremia/inappropriate ADH secretion, kidney failure.

7 DRUG INTERACTIONS

7.1 CYP2D6 and CYP3A4 Inhibitors

Drugs that inhibit CYP2D6 (such as desipramine, paroxetine, ritonavir, or sertraline) and CYP3A4 (such as ketoconazole, ritonavir, saquinavir, erythromycin, or grapefruit juice) can be expected to cause increased plasma levels of propafenone. The combination of CYP3A4 inhibition and either CYP2D6 deficiency or CYP2D6 inhibition with administration of propafenone may increase the risk of adverse reactions, including proarrhythmia. Therefore, simultaneous use of RYTHMOL with both a CYP2D6 inhibitor and a CYP3A4 inhibitor should be avoided [see Warnings and Precautions (5.4), Dosage and Administration (2)].

Amiodarone: Concomitant administration of propafenone and amiodarone can affect conduction and repolarization and is not recommended.

Cimetidine: Concomitant administration of propafenone immediate-release tablets and cimetidine in 12 healthy subjects resulted in a 20% increase in steady-state plasma concentrations of propafenone.

Fluoxetine: Concomitant administration of propafenone and fluoxetine in extensive metabolizers increased the S-propafenone C_max and AUC by 39% and 50%, respectively, and the R propafenone C_max and AUC by 71% and 50%, respectively.

Quinidine: Small doses of quinidine completely inhibit the CYP2D6 hydroxylation metabolic pathway, making all patients, in effect, slow metabolizers [see Clinical Pharmacology (12)]. Concomitant administration of quinidine (50 mg 3 times daily) with 150 mg immediate-release propafenone 3 times daily decreased the clearance of propafenone by 60% in extensive metabolizers, making them slow metabolizers. Steady-state plasma concentrations more than doubled for propafenone, and decreased 50% for 5-OH-propafenone. A 100-mg dose of quinidine tripled steady-state concentrations of propafenone. Avoid concomitant use of propafenone and quinidine.

Rifampin: Concomitant administration of rifampin and propafenone in extensive metabolizers decreased the plasma concentrations of propafenone by 67% with a corresponding decrease of 5-OH-propafenone by 65%. The concentrations of norpropafenone increased by 30%. In slow metabolizers, there was a 50% decrease in propafenone plasma concentrations and an increase in the AUC and C_max of norpropafenone by 74% and 20%, respectively. Urinary excretion of propafenone and its metabolites decreased significantly. Similar results were noted in elderly patients: Both the AUC and C_max of propafenone decreased by 84%, with a corresponding decrease in AUC and C_max of 5-OH‑propafenone by 69% and 57%, respectively.

7.2 Digoxin

Concomitant use of propafenone and digoxin increased steady-state serum digoxin exposure (AUC) in patients by 60% to 270%, and decreased the clearance of digoxin by 31% to 67%. Monitor plasma digoxin levels of patients receiving propafenone and adjust digoxin dosage as needed.

7.3 Warfarin

The concomitant administration of propafenone and warfarin increased warfarin plasma concentrations at steady state by 39% in healthy volunteers and prolonged the prothrombin time (PT) in patients taking warfarin. Adjust the warfarin dose as needed by monitoring INR (international normalized ratio).

7.4 Orlistat

Orlistat may limit the fraction of propafenone available for absorption. In postmarketing reports, abrupt cessation of orlistat in patients stabilized on propafenone has resulted in severe adverse events including convulsions, atrioventricular block, and acute circulatory failure.

7.5 Beta-Antagonists

Concomitant use of propafenone and propranolol in healthy subjects increased propranolol plasma concentrations at steady state by 113%. In 4 patients, administration of metoprolol with propafenone increased the metoprolol plasma concentrations at steady state by 100% to 400%. The pharmacokinetics of propafenone was not affected by the coadministration of either propranolol or metoprolol. In clinical trials using propafenone immediate-release tablets, subjects who were receiving beta-blockers concurrently did not experience an increased incidence of side effects.

7.6 Lidocaine

No significant effects on the pharmacokinetics of propafenone or lidocaine have been seen following their concomitant use in patients. However, concomitant use of propafenone and lidocaine has been reported to increase the risks of central nervous system side effects of lidocaine.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Pregnancy Category C. There are no adequate and well-controlled studies in pregnant women. RYTHMOL should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Animal Data: Teratogenic Effects: Propafenone has been shown to be embryotoxic (decreased survival) in rabbits and rats when given in oral maternally toxic doses of 150 mg/kg day (about 3 times the maximum recommended human dose [MRHD] on a mg/m² basis) and 600 mg/kg/day (about 6 times the MRHD on a mg/m² basis), respectively. Although maternally tolerated doses (up to 270 mg/kg/day, about 3 times the MRHD on a mg/m² basis) produced no evidence of embryotoxicity in rats; post-implantation loss was elevated in all rabbit treatment groups (doses as low as 15 mg/kg/day, about 1/3 the MRHD on a mg/m² basis).

Non-teratogenic Effects: In a study in which female rats received daily oral doses of propafenone from mid-gestation through weaning of their offspring, doses as low as 90 mg/kg/day (equivalent to the MRHD on a mg/m² basis) produced increases in maternal deaths. Doses of 360 or more mg/kg/day (4 or more times the MRHD on a mg/m² basis) resulted in reductions in neonatal survival, body weight gain, and physiological development.

8.2 Labor and Delivery

It is not known whether the use of propafenone during labor or delivery has immediate or delayed adverse effects on the fetus, or whether it prolongs the duration of labor or increases the need for forceps delivery or other obstetrical intervention.

8.3 Nursing Mothers

Propafenone is excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from propafenone, decide whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

8.4 Pediatric Use

The safety and effectiveness of propafenone in pediatric patients have not been established.

8.5 Geriatric Use

Clinical trials of RYTHMOL did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger subjects. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

10 OVERDOSAGE

The symptoms of overdosage may include hypotension, somnolence, bradycardia, intra-atrial and intraventricular conduction disturbances, and rarely, convulsions and high-grade ventricular arrhythmias. Defibrillation, as well as infusion of dopamine and isoproterenol have been effective in controlling abnormal rhythm and blood pressure. Convulsions have been alleviated with intravenous diazepam. General supportive measures such as mechanical respiratory assistance and external cardiac massage may be necessary.

The hemodialysis of propafenone in patients with an overdose is expected to be of limited value in the removal of propafenone as a result of both its high protein binding (>95%) and large volume of distribution.

11 DESCRIPTION

RYTHMOL (propafenone hydrochloride) is an antiarrhythmic drug supplied in scored, film-coated tablets of 150 and 225 mg for oral administration. Propafenone has some structural similarities to beta-blocking agents.

Chemically, propafenone hydrochloride (HCl) is 2’-[2-hydroxy-3-(propylamino)-propoxy]-3-phenylpropiophenone hydrochloride, with a molecular weight of 377.92. The molecular formula is C₂₁H₂₇NO₃•HCl. The structural formula of propafenone HCl is given below: