propafenone, Rythmol, Rythmol SR

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GENERIC NAME: propafenone

BRAND NAME: Rythmol, Rythmol SR

DRUG CLASS AND MECHANISM: Propafenone is used to treat abnormalities of of rhythm in the heart. (It is an anti-arrhythmic drug.) The normal rhythm of the heart is dependent on the conduction of electrical impulses through the heart's muscle cells. The conduction of the impulses is dependent on channels in the muscle that transport sodium across the cells' borders. Propafenone blocks these channels and alters the conduction of electrical impulses through the muscle cells of the heart.. Propafenone slows conduction throughout the heart and is referred to as a type IC anti-arrhythmic. Propafenone also has some beta adrenergic receptor blocking properties, and, to a lesser extent, calcium channel blocking effect. These are class II and class IV properties, respectively. Propafenone also blocks electrical conduction through accessory pathways, such as seen in WPW syndrome. The FDA approved propafenone in November 1989.



PREPARATIONS: Tablets: 150, 225, and 300 mg. Capsules (extended Release): 225, 325, and 425 mg

STORAGE: Tablets should be stored at room temperature 15 to 30 C (59 to 86 F) in a tightly closed, light-resistant container.

PRESCRIBED FOR: Propafenone is an anti-arrhythmic agent approved for use in patients with life-threatening ventricular arrhythmias, such as ventricular tachycardia. Propafenone is also effective in suppressing the recurrence of atrial fibrillation and supra-ventricular tachycardia once normal sinus rhythm has been restored. Propafenone is at least as effective as any other type I agent in converting atrial fibrillation to normal sinus rhythm. Propafenone is effective in atrial tachycardia, AV nodal tachycardia, and bypass tract tachycardias.

DOSING: The initial dose is 150 mg every 8 hours of immediate release tablets. The dose may be increased at 3 to 4 day intervals to 225 mg every 8 hours and, if needed, to 300 mg every 8 hours.

When using extended release capsules the initial dose is 225 mg every 12 hours. The dose may be increased at minimum 5 day intervals to 325 every 12 hours and if necessary to 425 mg every 12 hours. The dose should be reduced in patients with liver failure. Propafenone is given with or without food.

DRUG INTERACTIONS: Quinidine (Quinidine Gluconate, Quinidine Sulfate) and fluoxetine (Prozac) inhibit the metabolism of propafenone. Therefore, they should not be combined with propafenone.

Propafenone increases the levels of digoxin (Lanoxin), warfarin (Coumadin), and beta blockers (for example, metoprolol [Lopressor, Toprol XL], propranolol [Inderal, InnoPran]). The dose of the interacting drugs may need to be reduced.

Rifampin increases the metabolism of propafenone, decreasing blood levels of propafenone.

Orlistat (Xenical) may reduce the absorption of propafenone. Stopping orlistat in patients stabilized on propafenone may result in propafenone toxicity because more propafenone will be absorbed after discontinuation of orlistat.

Propafenone may alter pacing and sensing thresholds of pacemakers and defibrillators. These devices should be re-programmed and closely monitored. Safety and efficacy in children has not been established.

PREGNANCY: Safety and efficacy in pregnant women has not been established.

NURSING MOTHERS: Propafenone is excreted in breast-milk. Mothers should decide whether to stop nursing or discontinue propafenone.

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