Propafenone

May alter pacemaker thresholds

Elevated ANA titers reported with use; may consider discontinuing therapy in symptomatic patients with positive ANA titers

Use caution in patients with hematologic disorders, myasthenia gravis (may exacerbate condition), hepatic/renal impairment

Use with caution in patients with hypersensitivity to propranolol

There is a potential for increased mortality post-MI, as with encainide and flecainide (other class ICs)

May cause new or worsened arrhythmias; proarrhythmic effects include sudden death and life-threatening ventricular arrhythmias such as ventricular fibrillation, ventricular tachycardia, asystole, and torsade de pointes; important to evaluate patient electrocardiographically prior to and during therapy to determine whether response supports continued treatment; because propafenone prolongs QRS interval in electrocardiogram, changes in the QT interval are difficult to interpret

Through CYP3A inhibition, grapefruit juice consumption may decrease elimination (ie, increase serum levels)

Correct electrolyte imbalance, especially hypomagnesemia or hypokalemia before initiating therapy and throughout

Plasma concentration has poor correlation to antiarrhythmia effect

New or worsening HF may occur; propafenone exerts a negative inotropic activity on myocardium as well as beta-blockade effects and may provoke overt heart failure; CHF attributable to propafenone HCl develops rarely (less than 0.2%) in subjects with ventricular arrhythmia who had no previous history of CHF

Slows AV conduction and may cause AV block

Brugada syndrome may be unmasked after exposure to propafenone; perform ECG after initiation and discontinue the drug if changes are suggestive of Brugada Syndrome

Agranulocytosis reported (most within first 2 months of treatment)

Highly metabolized by liver; severe liver impairment increases bioavailability by 70%; carefully monitor patients with impaired hepatic function for excessive pharmacological effects