Rythmol SR 325mg Capsules

Propafenone is a Class Ic antiarrhythmic agent. It exerts its electrophysiological effects by blocking the fast inward sodium current (INa) in myocardial cells, leading to a dose-dependent reduction in the maximum rate of depolarization (Vmax) of the action potential. This results in a decrease in impulse conduction velocity in the atria, AV node, and ventricles. It also has weak beta-blocking activity and calcium channel blocking activity, but its primary antiarrhythmic effect is due to sodium channel blockade.

Serious 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 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
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 medical help right away if you experience:
+ Shortness of breath
+ Sudden weight gain
+ Irregular heartbeat
+ New or worsening swelling in the arms or legs
Low white blood cell counts have been reported with similar medications, increasing the risk of infection. Rarely, these infections can be fatal. If you have a history of low white blood cell counts, tell your doctor. Contact your doctor immediately if you notice 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, fatigue, or weakness
Upset stomach or vomiting
Constipation
Changes in taste
Headache
Anxiety
* Symptoms 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, 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 defibrillator or pacemaker, consult with your doctor before starting this medication. An electrocardiogram (ECG) will be required before initiating treatment and at regular intervals during therapy. 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.

This medication may decrease sperm count, which could affect 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
• Saquinavir
• Lopinavir/Ritonavir
• Other strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, clarithromycin, telithromycin) in patients who are also poor metabolizers of CYP2D6.
• Quinidine (in extensive metabolizers of CYP2D6, as it converts them to poor metabolizers)

• Digoxin (increases digoxin levels significantly)
• Warfarin (potentiates anticoagulant effect, increases INR)
• Beta-blockers (e.g., metoprolol, propranolol - increased levels of beta-blocker)
• Local anesthetics (e.g., lidocaine - increased risk of CNS and cardiac toxicity)
• Other antiarrhythmics (e.g., amiodarone, flecainide, quinidine - increased risk of proarrhythmia and toxicity)
• CYP2D6 inhibitors (e.g., fluoxetine, paroxetine, sertraline - increased propafenone levels)
• CYP3A4 inhibitors (e.g., grapefruit juice, diltiazem, verapamil - increased propafenone levels)
• Cimetidine (increases propafenone levels)

• Rifampin (decreases propafenone levels)
• Phenobarbital (decreases propafenone levels)
• Theophylline (increases theophylline levels)
• Cyclosporine (increases cyclosporine levels)
• Orlistat (may reduce absorption of propafenone)

• Not specifically categorized as minor for clinically significant interactions; most interactions are moderate to major due to narrow therapeutic index.

• Palpitations (new or worsening)
• Dizziness
• Lightheadedness
• Syncope (fainting)
• Chest pain
• Shortness of breath
• Swelling of ankles/feet (signs of heart failure)
• Unusual fatigue
• Yellowing of skin or eyes (jaundice)
• Dark urine
• Nausea/vomiting
• Tremor
• Blurred vision

Propafenone is 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 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.

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

Elderly patients may be more sensitive to the effects of propafenone due to age-related decreases in renal and hepatic function. Start with lower doses and titrate slowly, monitoring closely for adverse effects and drug levels if appropriate. Consider reduced doses in patients with impaired hepatic or renal function.

• Propafenone is a Class Ic antiarrhythmic and should NOT be used in patients with structural heart disease (e.g., history of MI, heart failure, significant valvular disease) due to increased mortality risk (Black Box Warning).
• Genetic polymorphism of CYP2D6 significantly impacts propafenone metabolism. Extensive metabolizers (EMs) have a shorter half-life and require higher doses than poor metabolizers (PMs). Quinidine can convert EMs to PMs.
• The primary ECG change to monitor for toxicity is QRS widening. If QRS duration increases by more than 25% from baseline, consider dose reduction.
• Propafenone has weak beta-blocking activity, which can contribute to bradycardia or worsening heart failure, especially in susceptible patients.
• Significant drug interactions exist, particularly with digoxin, warfarin, beta-blockers, and CYP inhibitors/inducers. Close monitoring and dose adjustments are often required.
• Rythmol SR capsules must be swallowed whole; crushing or chewing can lead to rapid release and increased risk of toxicity.

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

If your symptoms or health issues persist or worsen, it is essential to contact your doctor promptly. 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 detailed information about the overdose, including the medication taken, the amount, and the time it occurred.