Rythmol SR 225mg Capsules

Propafenone is a Class IC antiarrhythmic agent. It exerts its effects by blocking fast voltage-gated sodium channels in myocardial cells, leading to a 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 has weak beta-blocking and calcium channel blocking properties.

Urgent Side Effects: Seek Medical Help Right Away

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

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
Abnormal heartbeat, including fast or slow heart rate
Severe dizziness or fainting
New or worsening abnormal heartbeat
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 immediate medical attention if you experience:
+ Shortness of breath
+ Sudden weight gain
+ Abnormal 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 count, notify your doctor. Contact your doctor right away 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:

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 prescription or over-the-counter medications, 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 or health problems that may affect your use of this medication. To ensure your safety, it is vital to:

Inform your doctor and pharmacist about all your medications (prescription and over-the-counter), natural products, vitamins, and health conditions.
Verify that it is safe to take this medication with all your other medications and health conditions.
* Never start, stop, or change the dose of any medication without first 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 Antinuclear Antibody Test (ANA test) result, consult with your doctor to discuss any potential implications. Additionally, if you have myasthenia gravis, inform your doctor, as this condition may worsen during treatment with this medication. If you experience any worsening of symptoms, contact your doctor promptly.

If you have a pacemaker or defibrillator, consult with your doctor before starting this medication. An electrocardiogram (ECG) will be required before initiating treatment and at various points during treatment. Discuss the details with your doctor.

To avoid potential interactions, refrain from consuming grapefruit and grapefruit juice while taking this medication.

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

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.

If you are pregnant, planning to become pregnant, or breastfeeding, inform your doctor to discuss the potential benefits and risks of this medication to both you and your baby.

• Ritonavir (significant increase in propafenone levels)
• Quinidine (inhibits CYP2D6, leading to increased propafenone levels)
• Amiodarone (increased propafenone levels and proarrhythmic risk)
• Cimetidine (increased propafenone levels)
• Local anesthetics (additive CNS and cardiac effects)

• Digoxin (propafenone increases digoxin levels)
• Warfarin (propafenone increases warfarin levels, increasing INR)
• Beta-blockers (additive negative inotropic/chronotropic effects, increased beta-blocker levels)
• Calcium channel blockers (e.g., verapamil, diltiazem - additive negative inotropic/chronotropic effects, increased propafenone levels)
• Other antiarrhythmics (increased proarrhythmic risk)
• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine, sertraline - significantly increase propafenone levels)
• CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin - increase propafenone levels)

• Rifampin (CYP inducers, decrease propafenone levels)
• Phenobarbital, Phenytoin (CYP inducers, decrease propafenone levels)
• Grapefruit juice (may inhibit CYP3A4, increasing propafenone levels)
• Lidocaine (additive CNS and cardiac effects)
• Theophylline (propafenone may increase theophylline levels)

• Antacids (may affect absorption, separate administration)
• Food (minor increase in absorption, generally not clinically significant)

• Dizziness
• Lightheadedness
• Syncope
• Palpitations (new or worsening)
• Shortness of breath
• Chest pain
• Fatigue
• Nausea
• Vomiting
• Unusual taste (metallic taste)
• Blurred vision
• Signs of heart failure (e.g., swelling in ankles, rapid weight gain)

Propafenone is classified as Pregnancy Category C. Animal studies have shown adverse effects on the fetus, but there are no adequate and well-controlled studies in pregnant women. It should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Propafenone is excreted into human breast milk. Due to the potential for serious adverse reactions in the nursing infant, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother. The American Academy of Pediatrics considers it a drug for which the effect on nursing infants is unknown but may be of concern (L3).

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

Elderly patients may be more susceptible to the adverse effects of propafenone, particularly proarrhythmia and CNS effects. Start with lower doses and titrate slowly, monitoring closely for adverse effects and drug levels. Renal and hepatic function should be carefully assessed.

• Propafenone is a Class IC antiarrhythmic with a significant Black Box Warning regarding increased mortality in patients with structural heart disease. Always rule out structural heart disease before initiation.
• Genetic polymorphism of CYP2D6 significantly impacts propafenone metabolism and half-life. Poor metabolizers will have higher drug levels and a longer half-life, requiring lower doses.
• Monitor ECG (PR, QRS, QT intervals) closely during initiation and dose titration. A QRS widening of >25% from baseline or significant PR prolongation warrants dose reduction or discontinuation.
• Metallic taste is a common and often bothersome side effect that can impact adherence.
• Propafenone has weak beta-blocking and calcium channel blocking activity, which can contribute to bradycardia or hypotension, especially when co-administered with other agents having similar effects.
• Electrolyte imbalances (especially hypokalemia and hypomagnesemia) must be corrected before and during propafenone therapy to minimize proarrhythmic risk.

• Flecainide (another Class IC antiarrhythmic, similar efficacy and risks)
• Amiodarone (Class III antiarrhythmic, broader spectrum, different side effect profile)
• Dofetilide (Class III antiarrhythmic)
• Sotalol (Class III and beta-blocker)
• Dronedarone (Class III antiarrhythmic)
• Beta-blockers (e.g., metoprolol, atenolol - for rate control or rhythm control in some cases)
• Calcium channel blockers (e.g., diltiazem, verapamil - for rate control)
• Catheter ablation (non-pharmacological intervention for arrhythmias)

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's a good idea to check with your pharmacist. If you have any questions or concerns about this medication, don't hesitate to discuss them 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 information about the medication taken, the amount, and the time it happened.