PROPAFENONE HYDROCHLORIDE 150MG TABLETS Including dosage instructions and possible side effects.

Patient information for PROPAFENONE HYDROCHLORIDE 150MG TABLETS Including dosage instructions and possible side effects.

Propafenone hydrochloride is an antiarrhythmic drug supplied in scored, film-coated tablets of 150, 225 and 300 mg for oral administration. Propafenone has some structural similarities to beta-blocking agents.

CLINICAL PHARMACOLOGY

Mechanism of Action

Propafenone is a Class 1C antiarrhythmic drug with local anesthetic effects, and a direct stabilizing action on myocardial membranes. The electrophysiological effect of propafenone manifests itself in a reduction of upstroke velocity (Phase 0) of the monophasic action potential. In Purkinje fibers, and to a lesser extent myocardial fibers, propafenone reduces the fast inward current carried by sodium ions. Diastolic excitability threshold is increased and effective refractory period prolonged. Propafenone reduces spontaneous automaticity and depresses triggered activity.

Studies in anesthetized dogs and isolated organ preparations show that propafenone has beta-sympatholytic activity at about 1/50 the potency of propranolol. Clinical studies employing isoproterenol challenge and exercise testing after single doses of propafenone indicate a beta-adrenergic blocking potency (per mg) about 1/40 that of propranolol in man. In clinical trials, resting heart rate decreases of about 8% were noted at the higher end of the therapeutic plasma concentration range. At very high concentrations in vitro, propafenone can inhibit the slow inward current carried by calcium, but this calcium antagonist effect probably does not contribute to antiarrhythmic efficacy. Propafenone has local anesthetic activity approximately equal to procaine.

Electrophysiology

Electrophysiology studies in patients with ventricular tachycardia (VT) have shown that propafenone HCl prolongs atrioventricular (AV) conduction while having little or no effect on sinus node function. Both AV nodal conduction time (AH interval) and His-Purkinje conduction time (HV interval) are prolonged. Propafenone has little or no effect on the atrial functional refractory period, but AV nodal functional and effective refractory periods are prolonged. In patients with Wolff-Parkinson-White (WPW) syndrome, propafenone reduces conduction and increases the effective refractory period of the accessory pathway in both directions. Propafenone slows conduction and consequently produces dose-related changes in the PR interval and QRS duration. QTc interval does not change.

INDICATIONS AND USAGE

In patients without structural heart disease, propafenone is indicated to prolong the time to recurrence of

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paroxysmal atrial fibrillation/flutter (PAF) associated with disabling symptoms.

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paroxysmal supraventricular tachycardia (PSVT) associated with disabling symptoms.

As with other agents, some patients with atrial flutter treated with propafenone have developed 1:1 conduction, producing an increase in ventricular rate. Concomitant treatment with drugs that increase the functional AV refractory period is recommended.
The use of propafenone HCl in patients with chronic atrial fibrillation has not been evaluated. Propafenone HCl should not be used to control ventricular rate during atrial fibrillation.
Propafenone HCl is also indicated for the treatment of

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documented ventricular arrhythmias, such as sustained ventricular tachycardia, that, in the judgment of the physician, are life-threatening. Because of the proarrhythmic effects of propafenone HCl, its use with lesser ventricular arrhythmias is not recommended, even if patients are symptomatic, and any use of the drug should be reserved for patients in whom, in the opinion of the physician, the potential benefits outweigh the risks.

Initiation of propafenone HCl treatment, as with other antiarrhythmics used to treat life-threatening ventricular arrhythmias, should be carried out in the hospital.
Propafenone HCl, like other antiarrhythmic drugs, has not been shown to enhance survival in patients with ventricular or atrial arrhythmias.

CONTRAINDICATIONS

Propafenone HCl is contraindicated in the presence of uncontrolled congestive heart failure, cardiogenic shock, sinoatrial, atrioventricular and intraventricular disorders of impulse generation and/or conduction (e.g., sick sinus node syndrome, atrioventricular block) in the absence of an artificial pacemaker, bradycardia, marked hypotension, bronchospastic disorders, manifest electrolyte imbalance, and known hypersensitivity to the drug.