propafenone, Rythmol, Rythmol SR (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

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.

SIDE EFFECTS: Common side effects include dizziness, blurred vision, anorexia, unusual taste, fatigue, nausea and vomiting. Chest pain, heart palpitations, and congestive heart failure may also occur. Because of its beta blocking activity, propafenone must be used with caution in patients with weak heart muscle (congestive heart failure), slow heart rate, any form of heart electrical conduction block, low blood pressure, or asthma. The most serious side effect of propafenone is the causing of serious life- threatening irregular heart rhythms (ventricular arrhythmias or pro-arrhythmia) or heart block. It is for this reason that propafenone is started and doses increased while patients are hospitalized in a monitored setting.

Reference: FDA Prescribing Information

Last Editorial Review: 7/18/2012

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