PROPAFENONE Drug Interactions: What You Need to Know

INTERACTIONS

• Inhibitors of CYP2D6, 1A2, and 3A4 may increase propafenone levels which may lead to cardiac arrhythmias. Simultaneous use with both a CYP3A4 and CYP2D6 inhibitor (or in patients with CYP2D6 deficiency) should be avoided. ( 7.1 )
• Propafenone may increase digoxin or warfarin levels. ( 7.2 , 7.3 )
• Orlistat may reduce propafenone concentrations. Abrupt cessation of orlistat in patients stable on propafenone hydrochloride extended-release capsules has resulted in convulsions, atrioventricular block, and circulatory failure. ( 7.4 )
• Concomitant use of lidocaine may increase central nervous system side effects. ( 7.6 )

7.1 CYP2D6 and CYP3A4 Inhibitors Drugs that inhibit CYP2D6 (such as desipramine, paroxetine, ritonavir, sertraline) and CYP3A4 (such as ketoconazole, ritonavir, saquinavir, erythromycin, and 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 propafenone hydrochloride extended-release capsules with both a CYP2D6 inhibitor and a CYP3A4 inhibitor should be avoided <span class="opacity-50 text-xs">[see Warnings and Precautions ( 5.4 ) and Dosage and Administration ( 2 )]</span>.

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 ( 12.3 )] . 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 poor metabolizers. Steady-state plasma concentrations increased by more than 2-fold for propafenone and decreased 50% for 5-OH-propafenone. A 100 mg dose of quinidine increased steady-state concentrations of propafenone 3-fold. 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 poor 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, patients 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.

Propafenone hydrochloride extended-release capsules are 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
• Heart failure ( 4 )
• Cardiogenic shock ( 4 )
• Sinoatrial, atrioventricular, and intraventricular disorders of impulse generation and/or conduction in the absence of pacemaker ( 4 )
• Known Brugada Syndrome ( 4 )
• Bradycardia ( 4 )
• Marked hypotension ( 4 )
• Bronchospastic disorders and severe obstructive pulmonary disease ( 4 )
• Marked electrolyte imbalance ( 4 )

AND PRECAUTIONS May cause new or worsened arrhythmias. Evaluate patients via ECG prior to and during therapy. (5.1) Propafenone hydrochloride extended-release capsules may unmask Brugada or Brugada-like Syndrome. Evaluate patients via ECG after initiation of therapy. (4, 5.2) Avoid use with other antiarrhythmic agents or drugs that prolong the QT interval. (5.3) Avoid simultaneous use of propafenone with both a cytochrome P450 2D6 (CYP2D6) inhibitor and a 3A4 inhibitor (CYP3A4). (5.4) May provoke overt heart failure. (5.5) May cause dose-related first-degree AV block or other conduction disturbances. Should not be given to patients with conduction defects in absence of a pacemaker. (5.6) May affect artificial pacemakers. Pacemakers should be monitored during therapy. (5.7) Agranulocytosis: Patients should report signs of infection. (5.8) Administer cautiously to patients with impaired hepatic and renal function. (5.9, 5.10) Exacerbation of myasthenia gravis has been reported. (5.11) Propafenone hydrochloride extended-release capsules 225 mg & 325 mg contains FD&C Yellow No. 5 (tartrazine) which may cause allergic-type reactions (including bronchial asthma) in certain susceptible persons. Although the overall incidence of FD&C Yellow No. 5 (tartrazine) sensitivity in the general population is low, it is frequently seen in patients who also have aspirin hypersensitivity.

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 torsades 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 propafenone hydrochloride extended-release capsules be evaluated electrocardiographically prior to and during therapy to determine whether the response to propafenone hydrochloride extended-release capsules supports continued treatment. Because propafenone prolongs the QRS interval in the electrocardiogram, changes in the QT interval are difficult to interpret <span class="opacity-50 text-xs">[see Clinical Pharmacology (12.2)]</span>. In the RYTHMOL SR Atrial Fibrillation Trial (RAFT) trial <span class="opacity-50 text-xs">[see Clinical Studies (14)]</span>, there were too few deaths to assess the long-term risk to patients. There were 5 deaths, 3 in the pooled group for propafenone hydrochloride extended-release capsules (0.8%), and 2 in the placebo group (1.6%). In the overall database of 8 trials of propafenone hydrochloride extended-release capsules and immediate-release propafenone hydrochloride, 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. In a U.S. uncontrolled, open-label, multicenter trial using the immediate-release formulation in patients with symptomatic supraventricular tachycardia (SVT), 1.9% (9/474) of these patients experienced ventricular tachycardia (VT) or ventricular fibrillation (VF) during the trial. However, in 4 of the 9 patients, the ventricular tachycardia was of atrial origin. Six of the 9 patients that developed ventricular arrhythmias did so within 14 days of onset of therapy.

About

2.3% (11/474) of all patients had recurrence of SVT during the trial which could have been a change in the patients' 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, torsades de pointes, asystole, and death. Overall in clinical trials with propafenone hydrochloride immediate-release (which included patients treated for ventricular arrhythmias, atrial fibrillation/flutter, and PSVT), 4.7% of all patients 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 patients 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 patients with less serious or benign arrhythmias, which include patients 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 proarrhythmia is present throughout treatment.

5.2 Unmasking Brugada Syndrome Brugada Syndrome may be unmasked after exposure to propafenone hydrochloride extended-release capsules. Perform an ECG after initiation of propafenone hydrochloride extended-release capsules and discontinue the drug if changes are suggestive of Brugada Syndrome <span class="opacity-50 text-xs">[see Contraindications (4)]</span> .

5.3 Use with Drugs that Prolong the QT Interval and Antiarrhythmic Agents The use of propafenone hydrochloride extended-release capsules 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 propafenone hydrochloride extended-release capsules. 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 U.S. population are naturally deficient in CYP2D6 activity and other demographic groups are deficient to a somewhat lesser extent. 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 propafenone hydrochloride extended-release capsules 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 the U.S. trial (RAFT) in patients with symptomatic AF, heart failure was reported in 4 (1%) patients receiving propafenone hydrochloride extended-release capsules (all doses) compared with 1 (0.8%) patient receiving placebo. Proarrhythmic effects more likely occur when propafenone is administered to patients with heart failure (NYHA III and IV) or severe myocardial ischemia <span class="opacity-50 text-xs">[see Contraindications (4)]</span> . In clinical trial experience with propafenone hydrochloride immediate-release, new or worsened congestive heart failure has been reported in 3.7% of patients with ventricular arrhythmia. These events were more likely in subjects with pre-existing heart failure and coronary artery disease. New onset of heart failure attributable to propafenone developed in less than 0.2% of patients with ventricular arrhythmia and in 1.9% of patients with paroxysmal AF or PSVT.

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 <span class="opacity-50 text-xs">[see Contraindications (4), Clinical Pharmacology (12.2)]</span> . In a U.S. trial (RAFT) in 523 patients with a history of symptomatic AF treated with propafenone hydrochloride extended-release capsules, sinus bradycardia (rate less than 50 beats/min) was reported with the same frequency with propafenone hydrochloride extended-release capsules 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 when given propafenone hydrochloride immediate-release tablets.

In

8 patients with moderate to severe liver disease administered propafenone hydrochloride immediate-release tablets, the mean half-life was approximately 9 hours. No trials have compared bioavailability of propafenone from propafenone hydrochloride extended-release capsules in patients with normal and impaired hepatic function. 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 propafenone hydrochloride immediate-release tablets. No trials have been performed to assess the percentage of metabolites eliminated in the urine following the administration of propafenone hydrochloride extended-release capsules. 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 Risk of Allergic Reactions Due to Tartrazine Propafenone hydrochloride extended-release capsules, 225 mg and 325 mg contains FD&amp;C Yellow No. 5 (tartrazine) which may cause allergic-type reactions (including bronchial asthma) in certain susceptible persons. Although the overall incidence of FD&amp;C Yellow No. 5 (tartrazine) sensitivity in the general population is low, it is frequently seen in patients who also have aspirin hypersensitivity.