Rythmosin150 mg

Rythmosin is a Class IC antiarrhythmic agent used for the following indications, classified by strength of evidence:

Established / Approved Uses

• Life-threatening ventricular arrhythmias, such as documented sustained ventricular tachycardia, where the potential benefit outweighs the risk.
• Maintenance of normal sinus rhythm in patients with paroxysmal atrial fibrillation or atrial flutter and paroxysmal supraventricular tachycardia (PSVT), specifically in patients without structural heart disease (e.g. no significant coronary artery disease or reduced ejection fraction).

Guideline-Supported Use

• Used as part of a "pill-in-the-pocket" strategy for termination of recent-onset atrial fibrillation in selected patients without structural heart disease, under physician guidance.

Rythmosin is not recommended for patients with structural heart disease because of an increased risk of proarrhythmia and mortality in this population. Use should be initiated and monitored by a physician experienced in treating cardiac arrhythmias.

Each tablet/capsule contains Propafenone Hydrochloride INN as the active ingredient, commonly available in immediate-release strengths (e.g. 150 mg, 300 mg) and extended-release strengths (e.g. 225 mg, 325 mg, 425 mg), along with pharmaceutically acceptable excipients. Please check the product label of the specific brand for the exact strength and excipient list.

Rythmosin is a Class IC antiarrhythmic drug that works by blocking fast sodium channels in cardiac cell membranes, thereby slowing conduction velocity in the heart. It also has mild, non-selective beta-adrenergic blocking activity. Rythmosin is used to treat certain serious irregular heart rhythms (arrhythmias), including life-threatening ventricular arrhythmias and, in appropriately selected patients, supraventricular arrhythmias such as atrial fibrillation.

Because Rythmosin can itself cause new or worsened arrhythmias (a proarrhythmic effect), treatment is generally started in a setting where cardiac rhythm can be monitored, and it requires ongoing supervision by a physician.

Rythmosin belongs to the Class IC antiarrhythmic group of medicines (Vaughan Williams classification), a subclass of sodium channel blocking antiarrhythmic drugs.

Propafenone Hydrochloride is a Class IC antiarrhythmic agent. Its primary mechanism is blockade of the fast inward sodium current in cardiac myocytes, which slows the rate of rise of the action potential (phase 0) and reduces conduction velocity in atrial, ventricular, and His-Purkinje tissue, with a relatively slow rate of dissociation from sodium channels ("use-dependent" block). Propafenone Hydrochloride also has weak calcium-channel blocking activity and mild, non-selective beta-adrenergic receptor blocking activity, which contributes to its antiarrhythmic and negative inotropic/chronotropic effects.

Pharmacokinetics: Propafenone Hydrochloride is well absorbed orally but undergoes extensive first-pass hepatic metabolism via the cytochrome P450 2D6 (CYP2D6) enzyme, which is subject to genetic polymorphism. Extensive metabolizers convert Propafenone Hydrochloride rapidly to active metabolites (5-hydroxypropafenone and N-depropylpropafenone), while poor metabolizers (a small percentage of the population) achieve higher parent-drug plasma concentrations. Elimination is mainly hepatic, with metabolites excreted renally and in bile. Half-life varies (roughly 2 to 10 hours or more) depending on metabolizer status and dose.

Rythmosin may be taken with or without food; taking it consistently with regard to meals is advisable since food can affect absorption rate. Swallow extended-release capsules whole; do not crush, chew, or open them. Do not stop or alter the dose of Rythmosin without consulting the prescribing physician.

Rythmosin is metabolized by CYP2D6 and is itself a moderate inhibitor of CYP2D6 and CYP1A2, resulting in several clinically significant interactions:

• Digoxin: Rythmosin can increase serum digoxin concentrations; digoxin levels should be monitored and dose adjusted as needed.
• Warfarin and other anticoagulants: Rythmosin can increase prothrombin time/INR, raising bleeding risk; INR should be monitored closely when Rythmosin is started, stopped, or dose-adjusted.
• Beta-blockers (e.g. metoprolol, propranolol): Rythmosin can increase plasma levels of these drugs and has additive beta-blocking, negative inotropic and conduction-slowing effects; dose reduction of the beta-blocker may be needed.
• Other antiarrhythmics (e.g. quinidine, amiodarone) and CYP2D6 inhibitors (e.g. fluoxetine, paroxetine, ritonavir, ketoconazole): these can raise Rythmosin plasma concentrations and increase the risk of proarrhythmia and other toxicity.
• CYP3A4/CYP1A2 inducers (e.g. rifampin): may lower Rythmosin plasma concentrations, potentially reducing efficacy.
• Local anesthetics (e.g. during procedures): increased risk of central nervous system side effects due to additive effects.
• Cimetidine: can increase Rythmosin plasma concentrations.

Always inform the physician of all prescription, over-the-counter, and herbal products being used before starting Rythmosin.

Common side effects of Rythmosin include:

• Dizziness or light-headedness
• Unusual/metallic taste disturbance
• Nausea, vomiting, or constipation
• Blurred vision
• Fatigue or weakness
• Headache
• Palpitations

Less common but serious effects (seek prompt medical attention) include new or worsened arrhythmias (proarrhythmia), fainting, first-degree AV block or other conduction disturbances, worsening heart failure (shortness of breath, swelling), and bronchospasm (wheezing, difficulty breathing) in susceptible patients. See Precautions and Warnings for the proarrhythmia risk in detail.

Pregnancy: There are no adequate and well-controlled studies of Rythmosin in pregnant women. Rythmosin should be used during pregnancy only if the potential benefit to the mother clearly justifies the potential risk to the fetus. Use only under close physician supervision.

Lactation: It is not well established whether Rythmosin passes into human breast milk. Because of the potential for serious adverse effects in a nursing infant, a decision should be made whether to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother, and only after consulting a physician.

Proarrhythmia: Like other Class IC antiarrhythmics, Rythmosin can cause new or worsened ventricular arrhythmias, some of which can be life-threatening. Treatment should generally be initiated in a setting equipped for cardiac rhythm monitoring, with baseline and periodic ECG evaluation, typically under the supervision of a cardiologist/specialist.

Conduction disease: Rythmosin can unmask or worsen sinus node dysfunction and AV or intraventricular conduction disease; caution and ECG monitoring are needed, especially at treatment initiation or dose increases.

CYP2D6 metabolism: Plasma levels vary widely depending on CYP2D6 metabolizer status and concomitant CYP2D6 inhibitors/substrates (see Interactions); dose individualization and monitoring are important.

Heart failure: Use with caution in patients with any degree of left ventricular dysfunction because of negative inotropic effects.

Bronchospastic disease: Use with caution due to beta-blocking activity, which may worsen bronchospasm in susceptible patients.

Electrolyte imbalance: Correct hypokalemia or hyperkalemia before starting Rythmosin, as electrolyte disturbances can increase the risk of proarrhythmia.

Do not stop, skip, or change the dose of Rythmosin without medical advice, and do not share this medicine with others.

Overdose of Rythmosin can cause severe hypotension, marked bradycardia or heart block, widened QRS complex, ventricular arrhythmias, seizures, and, in severe cases, cardiac arrest. There is no specific antidote. If an overdose of Rythmosin is suspected, seek immediate medical attention or contact the nearest hospital/emergency service or a poison control center right away; do not attempt home treatment. Management in a hospital setting typically involves continuous cardiac monitoring and supportive care.

Store at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Elderly: Use Rythmosin with caution in elderly patients; start at the lower end of the dosing range and monitor closely, as they may have reduced hepatic/renal function and increased susceptibility to adverse effects.

Hepatic impairment: Substantially reduced doses and close monitoring are required (see Dosage and Administration) because Rythmosin undergoes extensive hepatic metabolism.

Renal impairment: Use with caution and monitor; formal dose adjustment guidance is limited.

Pediatric patients: Safety and efficacy have not been established (see Pediatric Uses).

Pregnancy and breastfeeding: See Pregnancy and Lactation.

Duration of treatment with Rythmosin is individualized by the treating physician based on the underlying arrhythmia, response to therapy, and ongoing cardiac monitoring. It may be used short-term (e.g. for termination of an acute arrhythmia episode under supervision) or long-term (e.g. for maintenance of sinus rhythm), and should be periodically reassessed. Do not stop Rythmosin abruptly without medical advice.

Propafenone Hydrochloride is classified as a Class IC antiarrhythmic agent (sodium channel blocker) with additional weak beta-adrenergic blocking and calcium-channel blocking properties.

Propafenone Hydrochloride works mainly by blocking fast sodium channels in the heart muscle cells, which slows the speed of electrical conduction through the atria, ventricles, and specialized conduction tissue (His-Purkinje system). This helps prevent or terminate abnormal, rapid heart rhythms. Propafenone Hydrochloride also has mild beta-blocking activity, which further contributes to slowing heart rate and conduction.

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The safety and efficacy of Rythmosin have not been established in pediatric patients. It is not routinely recommended for use in children. If a specialist determines that use is necessary for a serious arrhythmia in a child, it should only be undertaken by a pediatric cardiologist with close cardiac monitoring, using an individualized, carefully titrated dose.