propafenone (Rx)

Brand and Other Names:Rythmol, Rythmol SR
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Dosing & Uses


Dosage Forms & Strengths


  • 150mg
  • 225mg
  • 300mg

capsule, extended-release

  • 225mg
  • 325mg
  • 425mg

Ventricular Arrhythmias/Paroxysmal Supraventricular Tachycardia

IR: 150 mg PO q8hr; may increase to 225 mg q8hr after 3-4 days, and, if required, 300 mg q8hr; not to exceed 300 mg q8hr

Atrial Fibrillation/Flutter

IR: 150 mg PO q8hr; may increase to 225 mg q8hr after 3-4 days, and, if required, 300 mg q8hr; not to exceed 300 mg q8hr

ER: 225 mg PO q12hr initially; may increase dose q5Days to 325 mg PO q12hr OR 425 mg PO q12hr, if necessary

Dosing Considerations

Reduce dose in patients with significant widening of the QRS complex or 2nd or 3rd degree AV block

Dosing Modifications

Renal impairment: Not studied

Hepatic impairment: Administer 20-30% of normal IR dose and monitor closely; consider dose reduction if administering ER dose

Safety and efficacy not established



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            Adverse Effects


            Unusual taste (7-23%)

            Dizziness/lightheadedness (7-15%)

            N/V (3-11%)


            Constipation (4-8%)

            Headache (2-6%)

            Intraventricular conduction delay (4%)

            Fatigue (6%)

            Blurred vision (3%)

            Weakness (3%)

            Dyspnea (2%)

            Wild complex tachycardia (2%)

            Bradycardia (2%)

            Palpitations (2%)

            Tremor (2%)

            Anorexia (2%)

            Diarrhea (2%)

            Ataxia (2%)

            1°AV block (2-5%)

            Angina (5%)

            Palpitations (3%)

            CHF (2-3% )

            Chest pain (2%)

            Bradyarrhythmia (2%)

            AF (1%)

            Bundle branch block (1%)

            2nd degree AV block (1%)

            Hypotension (1%)

            Sinus arrest (1%)

            Frequency Not Defined




            Dry mouth


            Hepatotoxicity (rare)

            Systemic lupus erythematosus (rare)

            Bronchospasm (rare)

            Postmarketing Reports

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

            Neurologic/psychiatric: Abnormal dreams/speech/vision, apnea, coma, confusion, depression, memory loss, numbness, paresthesias, psychosis/mania, seizures, tinnitus, unusual smell sensation, vertigo

            Hepatic: Cholestasis, elevated LFTs, gastroenteritis, hepatitis

            Hematologic: Agranulocytosis, anemia, bruising, granulocytopenia, increased bleeding time, leukopenia, purpura, thrombocytopenia


            Eye irritation

            Hyponatremia/inappropriate ADH secretion


            Increased glucose

            Kidney failure

            Positive ANA

            Lupus erythematosus

            Muscle cramps

            Muscle weakness

            Nephrotic syndrome





            Black Box Warnings

            NHLBI’s Cardiac Arrhythmia Suppression Trial (CAST): Excessive mortality or nonfatal cardiac arrest (7.7%) shown with encainide or flecainide, compared with placebo (3%)

            Applicability of CAST results to other populations (eg, patients without recent MI) is uncertain; therefore, reserve use of class IC antiarrhythmics for life-threatening ventricular arrhythmias

            Considering known proarrhythmic properties of propafenone and lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, use should be reserved for patients with life-threatening ventricular arrhythmias



            Bradycardia, asthma/bronchospastic disorders or severe obstructive pulmonary disease, marked hypotension, cardiogenic shock, intraventricular disorders of impulse generation and/or conduction including sick sinus node and syndrome AV block (unless artificial pacemaker present), electrolyte imbalances, CHF, severe hypotension, myasthenia gravis

            Known Brugada syndrome

            Concomitant ritonavir therapy


            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


            Pregnancy & Lactation


            There are no studies in pregnant women; available data from published case reports and several decades of postmarketing experience with use in pregnancy have not identified any drug-associated risks of miscarriage, birth defects, or adverse maternal or fetal outcomes; untreated arrhythmias during pregnancy may pose a risk to pregnant woman and fetus; the drug and its metabolite, 5-OH-propafenone, cross the placenta in humans

            Incidence of VT is increased and may be more symptomatic during pregnancy; ventricular arrhythmias most often occur in pregnant women with underlying cardiomyopathy, congenital heart disease, valvular heart disease, or mitral valve prolapse; breakthrough arrhythmias may occur during pregnancy, as therapeutic treatment levels may be difficult to maintain due to increased volume of distribution and increased drug metabolism inherent in pregnant state

            The drug and its metabolite have been shown to cross placenta; adverse reactions such as fetal/neonatal arrhythmias have been associated with use of other antiarrhythmic agents by pregnant women; fetal/neonatal monitoring for signs and symptoms of arrhythmia is recommended during and after treatment of pregnant women

            Animal data

            • In animal studies, propafenone was not teratogenic; at maternally toxic doses (ranging from 2 to 6 times maximum recommended human dose [MRHD]), there was evidence of adverse developmental outcomes when administered to pregnant rabbits and rats during organogenesis or when administered to pregnant rats during mid-gestation through weaning of their offspring


            • Based on human and animal studies, may transiently impair spermatogenesis in males; reversible decreases in spermatogenesis have been demonstrated in monkeys, dogs, and rabbits after lethal or near-lethal intravenous doses of the drug

            Labor or Delivery

            • Risk of arrhythmias may increase during labor and delivery; patients should be monitored continuously for arrhythmias during labor and delivery


            Propafenone and its active metabolite, 5-OH-propafenone, are present in human milk, but levels are likely to be low; there are no data on effects on breastfed infant or on milk production

            The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for propafenone and any potential adverse effects on breastfed infant from propafenone or from underlying maternal condition

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.



            Mechanism of Action

            Class IC antiarrhythmic; slows conduction in cardiac tissue by altering transport of ion across membranes; causes slight prolongation of AV nodal refractory periods; decreases rate of rise of action potential without affecting its duration


            Bioavailability: 3.4% (150 mg IR); 10.6% (300 mg IR)

            Peak serum time: 2-3.5 hr (IR); 3-8 hr (ER)


            Protein bound: 95%

            Vd: 252 L (adults)


            Metabolism: Via CYP2D6 to 5-hydroxypropafenone; via CYP1A2 and CYP3A4 to N-depropylpropafenone

            Metabolites: 5-hydroxypropafenone (active), N-depropylpropafenone (active), at least 9 other metabolites

            Enzymes inhibited: CYP2D6


            Half-life: 2-10 hr (extensive metabolizers); 10-32 hr (poor metabolizers)

            Dialyzable: No (HD)

            Total body clearance: 1-1.3 L/kg/hr

            Excretion: Urine; feces


            Approximately 7-10% of whites and 3-8% of African Americans lack the capacity to metabolize CYP2D6 substrates and are classified as poor metabolizers (PMs)

            Increased exposure may lead to cardiac arrhythmias and exaggerated beta-adrenergic blocking activity

            Because of propafenone’s metabolism by CYP2D6, deficiency of this isoenzyme is potentially hazardous

            Genetic testing laboratories

            • The Roche Cytochrome AmpliChip P450 2D6/2C19 Genotyping and Phenotyping Assay can be used to identify 26 different alleles of CYP2D6
            • LabCorp (; testing for CYP2D6 variants




            FormularyPatient Discounts

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            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.