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(propafenone hydrochloride) Extended Release Capsules
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- In the National Heart, Lung and Blood Institute's Cardiac Arrhythmia Suppression Trial (CAST), a long-term, multi-center, randomized, double-blind study in patients with asymptomatic non-life-threatening ventricular arrhythmias who had a myocardial infarction more than 6 days but less than 2 years previously, an increased rate of death or reversed cardiac arrest rate (7.7%; 56/730) was seen in patients treated with encainide or flecainide (Class 1C antiarrhythmics) compared with that seen in patients assigned to placebo (3.0%; 22/725). The average duration of treatment with encainide or flecainide in this study was 10 months.
- The applicability of the CAST results to other populations (e.g., those without recent myocardial infarction) or other antiarrhythmic drugs is uncertain, but at present, it is prudent to consider any 1C antiarrhythmic to have a significant proarrhythmic risk in patients with structural heart disease. Given the lack of any evidence that these drugs improve survival, antiarrhythmic agents should generally be avoided in patients with non-life-threatening ventricular arrhythmias, even if the patients are experiencing unpleasant, but not life-threatening, symptoms or signs.
RYTHMOL SR (propafenone hydrochloride) is an antiarrhythmic drug supplied in extended-release capsules of 225, 325 and 425 mg for oral administration.
Chemically, propafenone hydrochloride is 2'-[2-hydroxy-3-(propylamino)-propoxy]-3-phenylpropiophenonehydrochloride, with a molecular weight of 377.92. The molecular formula is C21H27NO3•HCl.
Propafenone HC1 has some structural similarities to beta-blocking agents. The structural formula of propafenone HC1 is given below:
Propafenone HC1 occurs as colorless crystals or white crystalline powder with a very bitter taste. It is slightly soluble in water (20°C), chloroform and ethanol. Rythmol SR capsules are filled with cylindrical-shaped 2x2 mm microtablets containing propafenone and the following inactive ingredients: antifoam, gelatin, hypromellose, red iron oxide, magnesium stearate, shellac, sodium lauryl sulfate, sodium dodecyl sulfate, soy lecithin and titanium dioxide.
What are the possible side effects of propafenone (Rythmol, Rythmol SR)?
Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have a serious side effect such as:
- feeling short of breath, even with mild exertion;
- swelling, rapid weight gain;
- chest pain, rapid heart rate, pounding heartbeats or fluttering in your chest;
- fever, chills, sore throat, flu symptoms, weakness;
- confusion, unusual thoughts or behavior;
- seizure; or
- slow heart rate, weak...
What are the precautions when taking propafenose hydrochloride extended release capsules (Rythmol SR)?
Before taking propafenone, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.
Before using this medication, tell your doctor or pharmacist your medical history, especially of: breathing problems (such as asthma, chronic bronchitis, emphysema), kidney problems, liver problems, myasthenia gravis.
Propafenone may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can infrequently result in serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that require immediate medical attention. The risk of QT prolongation...
Last reviewed on RxList: 6/1/2011
This monograph has been modified to include the generic and brand name in many instances.
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