Propafenone 425mg SR Capsules

Propafenone is a Class IC antiarrhythmic agent that acts by blocking the fast inward sodium current (I_Na) in myocardial cells, leading to a concentration-dependent reduction in the maximum rate of depolarization (Vmax) of the action potential. This effect prolongs the effective refractory period and conduction time in the atria, AV node, and ventricles. It also possesses weak beta-adrenergic blocking activity and calcium channel blocking activity.

Serious Side Effects: Seek Medical Attention Immediately

Although rare, this medication can cause severe and potentially life-threatening side effects. If you experience any of the following symptoms, contact your doctor or seek medical help right away:

Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Chest pain or pressure
Fast or slow heartbeat
Severe dizziness or passing out
Abnormal heartbeat that is new or worse
Blurred eyesight

Heart-Related Side Effects

This medication can cause heart failure, including worsening of existing heart failure. If you have a history of heart disease, inform your doctor. Seek medical attention immediately if you experience:

Shortness of breath
Sudden weight gain
Abnormal heartbeat
Swelling in the arms or legs that is new or worse

Infection-Related Side Effects

Drugs like this one can cause low white blood cell counts, increasing the risk of infection. Rarely, these infections can be fatal. If you have a history of low white blood cell counts, inform your doctor. Seek medical attention immediately if you experience signs of infection, such as:

Fever
Chills
Sore throat

Other Side Effects

Most people do not experience significant side effects, but some may occur. If you experience any of the following side effects, contact your doctor or seek medical help if they bother you or do not go away:

Dizziness, tiredness, or weakness
Upset stomach or vomiting
Constipation
Change in taste
Headache
Anxiety
Signs of a common cold

Reporting Side Effects

This is not an exhaustive list of potential side effects. If you have questions or concerns about side effects, contact your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch.

Before Taking This Medication: Important Information to Share with Your Doctor

It is essential to inform your doctor about the following:

Any allergies you have to this medication, its components, or other substances, including foods and drugs. Describe the allergic reaction you experienced, such as symptoms and severity.
Certain health conditions, including:
+ Breathing or lung problems
+ Brugada syndrome
+ Electrolyte imbalances in your blood
+ Low blood pressure
+ Recent heart attack
+ Sick sinus syndrome or heart block without a functioning pacemaker
+ Shock caused by heart problems
+ Slow heartbeat
+ Heart failure
If you have been taking medications to treat abnormal heart rhythms
If you are taking any prescription or over-the-counter (OTC) medications, natural products, or vitamins that may interact with this medication. This includes certain medications used to treat HIV, infections, depression, and other conditions. Your doctor or pharmacist can advise you on potential interactions.

Please note that this is not an exhaustive list of all possible interactions. To ensure your safety, it is crucial to:

Inform your doctor and pharmacist about all your medications (prescription and OTC), natural products, and vitamins
Discuss your health problems and any potential interactions with this medication
Verify that it is safe to take this medication with your existing medications and health conditions
Avoid starting, stopping, or changing the dose of any medication without consulting your doctor.

It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication. Regular blood tests will be necessary, as directed by your doctor, to monitor your condition. Be sure to discuss any concerns or questions you have with your doctor.

This medication may interfere with certain laboratory tests, so it is crucial to notify all your healthcare providers and laboratory personnel that you are taking this drug.

If you have previously had an abnormal result on an Antinuclear Antibody Test (ANA test), consult with your doctor before starting treatment. Additionally, if you have myasthenia gravis, discuss your condition with your doctor, as this medication may worsen symptoms. If you experience any worsening of symptoms, contact your doctor promptly.

If you have a defibrillator or pacemaker, consult with your doctor before starting treatment. An electrocardiogram (ECG) will be required before initiating this medication and periodically during treatment. Discuss the schedule and any concerns with your doctor.

To avoid potential interactions, do not consume grapefruit or grapefruit juice while taking this medication.

Notify your doctor if you experience any signs of dehydration, such as excessive sweating, vomiting, diarrhea, decreased appetite, or unusual thirst.

This medication may decrease sperm count, which could affect fertility. If you have questions or concerns about this potential side effect, discuss them with your doctor.

If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor. It is essential to discuss the benefits and risks of this medication to both you and your baby to make an informed decision.

• Ritonavir (significant increase in propafenone levels)
• Quinidine (in poor metabolizers, can lead to excessive propafenone levels)

• Amiodarone (increased risk of proarrhythmia, QT prolongation)
• Digoxin (increases digoxin plasma levels, monitor digoxin levels)
• Warfarin (potentiates anticoagulant effect, monitor INR closely)
• Beta-blockers (e.g., metoprolol, propranolol; increased beta-blocker levels, monitor for bradycardia/hypotension)
• Local anesthetics (e.g., lidocaine; additive CNS effects)
• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine, sertraline; significantly increase propafenone levels)
• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin, grapefruit juice; increase propafenone levels)
• CYP1A2 inhibitors (e.g., cimetidine; increase propafenone levels)
• Rifampin (decreases propafenone levels, loss of efficacy)

• Phenobarbital, Phenytoin (may decrease propafenone levels)
• Theophylline (propafenone may increase theophylline levels)
• Cyclosporine (propafenone may increase cyclosporine levels)
• Orlistat (may reduce absorption of propafenone)

• Not available

• Palpitations
• Dizziness
• Lightheadedness
• Syncope (fainting)
• Chest pain
• Shortness of breath
• Fatigue
• Nausea
• Unusual taste (metallic taste)

Propafenone is classified as Pregnancy Category C. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown adverse effects at doses higher than human therapeutic doses.

Propafenone is excreted into breast milk. The amount is generally low, but there is a potential for adverse effects in the infant, particularly in poor metabolizers. The American Academy of Pediatrics considers it compatible with breastfeeding with caution. Monitor breastfed infants for bradycardia, feeding difficulties, and other signs of toxicity.

Safety and efficacy have not been established in pediatric patients. Use is generally not recommended.

Geriatric patients may be at increased risk for adverse effects due to age-related decreases in renal and hepatic function, and potential for polypharmacy. Start with lower doses and titrate slowly, monitoring closely for adverse effects and changes in ECG parameters.

• Propafenone SR is typically dosed every 12 hours. Do not crush or chew the capsules.
• Always rule out structural heart disease before initiating propafenone due to the black box warning regarding increased mortality.
• Correct electrolyte imbalances (especially hypokalemia and hypomagnesemia) before and during propafenone therapy to minimize proarrhythmic risk.
• Propafenone is a substrate and inhibitor of multiple CYP enzymes (2D6, 1A2, 3A4), leading to numerous significant drug interactions. Thorough medication reconciliation is crucial.
• Patients who are poor metabolizers of CYP2D6 will have significantly higher and more prolonged propafenone levels, requiring lower doses and careful monitoring.
• Monitor ECG (PR, QRS, QT intervals) regularly. A QRS prolongation of >25% from baseline or new conduction abnormalities warrants dose reduction or discontinuation.
• Metallic taste is a common, but usually benign, side effect.

• Other Class IC antiarrhythmics (e.g., Flecainide)
• Class III antiarrhythmics (e.g., Amiodarone, Dofetilide, Sotalol, Dronedarone)
• Beta-blockers (e.g., Metoprolol, Atenolol)
• Calcium channel blockers (e.g., Diltiazem, Verapamil)
• Catheter ablation procedures
• Cardioversion

If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more details. If you have any questions or concerns about your medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek emergency medical attention. When seeking help, be prepared to provide information about the medication taken, the amount, and the time it happened.