Rythmol SR 425mg Capsules

Propafenone is a Class Ic antiarrhythmic agent. It exerts its antiarrhythmic effects by blocking fast sodium channels in myocardial cells, leading to a significant reduction in the maximum rate of depolarization (Vmax) of the action potential. This results in a marked decrease in impulse conduction velocity in the atria, AV node, and ventricles, and a prolongation of the effective refractory period in the atria and AV node. It also possesses weak beta-adrenergic blocking activity and calcium channel blocking activity.

Urgent Side Effects: Seek Medical Help Right Away

While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek medical attention immediately:

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 fainting
Abnormal heartbeat that is new or worsening
Blurred vision

Important Warnings

Heart failure has been associated with this medication, and it can worsen existing heart disease. If you have a history of heart disease, inform your doctor. Seek medical attention immediately if you experience:
+ Shortness of breath
+ Sudden weight gain
+ Irregular heartbeat
+ Swelling in the arms or legs that is new or worsening
Low white blood cell counts have been reported with similar medications, increasing the risk of infection. 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 Possible Side Effects

Most people do not experience significant side effects, but some may occur. If you are bothered by any of the following side effects or if they persist, contact your doctor or seek medical attention:

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 possible 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, including allergies to this medication, its components, or other substances. Be sure to describe the allergic reaction and its symptoms.
Certain health conditions, such as:
+ 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 medications (prescription or over-the-counter), natural products, or vitamins that may interact with this medication. This includes certain medications used to treat HIV, infections, depression, and other conditions. There are many medications that should not be taken with this drug, so it is crucial to consult with your doctor or pharmacist to determine if any of your current medications are incompatible.

Please note that this is not an exhaustive list of all potential interactions. To ensure your safety, it is vital to inform your doctor and pharmacist about all your medications (prescription or over-the-counter), natural products, vitamins, and health conditions. Before starting, stopping, or changing the dose of any medication, always consult with your doctor to confirm that it is safe to do so in conjunction with this medication.

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 Antinuclear Antibody Test (ANA test), consult with your doctor to discuss any potential implications.

If you have myasthenia gravis, it is vital to discuss your condition with your doctor, as this medication may worsen symptoms. Monitor your condition closely and contact your doctor if your symptoms deteriorate. Additionally, if you have a defibrillator or pacemaker, consult with your doctor, as you will need to undergo an electrocardiogram (ECG) before starting treatment and at regular intervals during treatment.

To minimize potential interactions, avoid consuming grapefruit and grapefruit juice while taking this medication. If you experience excessive fluid loss, unusual sweating, vomiting, diarrhea, decreased appetite, or excessive thirst, notify your doctor promptly.

Men taking this medication should be aware that it may lower sperm counts, potentially affecting fertility. If you have concerns about fathering a child, discuss this with your doctor. It is also essential to inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding, as you will need to discuss the benefits and risks of this medication to both you and your baby.

• Ritonavir (strong CYP3A4 inhibitor)
• Quinidine (strong CYP2D6 inhibitor, can significantly increase propafenone levels in extensive metabolizers)
• Patients with structural heart disease (e.g., myocardial infarction, heart failure) due to proarrhythmic risk

• Digoxin (propafenone increases digoxin levels)
• Warfarin (propafenone increases INR)
• Beta-blockers (e.g., metoprolol, propranolol - increased levels of beta-blocker and propafenone, additive bradycardia/hypotension)
• Other antiarrhythmics (e.g., amiodarone, disopyramide, flecainide, quinidine - increased proarrhythmic risk, additive effects)
• Local anesthetics (e.g., lidocaine - increased CNS side effects)
• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine, sertraline - significantly increase propafenone levels)
• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin, grapefruit juice - increase propafenone levels)
• CYP1A2 inhibitors (e.g., cimetidine - increase propafenone levels)
• CYP inducers (e.g., rifampin, phenobarbital - decrease propafenone levels)

• Theophylline (propafenone may increase theophylline levels)
• Cyclosporine (propafenone may increase cyclosporine levels)
• Cimetidine (may increase propafenone levels)
• Grapefruit juice (may increase propafenone levels)

• Not specifically categorized as minor, but caution with any drug affecting cardiac conduction or CYP enzymes.

• New or worsening arrhythmias (proarrhythmia)
• Dizziness
• Lightheadedness
• Syncope
• Shortness of breath
• Chest pain
• Palpitations
• Fatigue
• Nausea
• Vomiting
• Constipation
• Blurred vision
• Tremor
• Unusual bleeding or bruising (if on anticoagulants)

Category C. Should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Animal studies have shown adverse effects, but there are no adequate and well-controlled studies in pregnant women.

L3 (Moderately Safe). Propafenone and its active metabolite are excreted into breast milk. While the amount is small, potential for adverse effects on the infant (e.g., bradycardia, proarrhythmia) exists. Weigh benefits vs. risks; monitor infant for adverse effects.

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

Use with caution. Elderly patients may be more sensitive to the effects of propafenone, particularly regarding conduction disturbances and CNS effects. Start with lower doses and titrate slowly. Monitor renal and hepatic function closely.

• Propafenone is a 'pill-in-the-pocket' option for select patients with infrequent, symptomatic AF without structural heart disease.
• Always rule out structural heart disease (e.g., by echocardiogram) before initiating propafenone due to the Black Box Warning.
• Genetic polymorphism of CYP2D6 significantly impacts propafenone metabolism and half-life. Poor metabolizers will have higher drug levels and longer half-lives, requiring lower doses.
• Monitor ECG closely for QRS widening (>25% or >120 ms) as this indicates excessive sodium channel blockade and increased proarrhythmic risk.
• Correct hypokalemia and hypomagnesemia prior to and during propafenone therapy to minimize proarrhythmic risk.
• Patients should be hospitalized for initial dose titration and monitoring, especially for those with significant comorbidities or at higher risk of proarrhythmia.

• Flecainide (another Class Ic antiarrhythmic)
• Amiodarone (Class III antiarrhythmic)
• Dofetilide (Class III antiarrhythmic)
• Sotalol (Class III antiarrhythmic with beta-blocking properties)
• Dronedarone (Class III antiarrhythmic)
• Catheter ablation (non-pharmacological)

If your symptoms or health issues persist or worsen, it is 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 it is a good idea to check with your pharmacist for more information. If you have any questions or concerns about this medication, consult with 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 details about the overdose, including the medication taken, the amount, and the time it occurred.