Propafenone is a class Ic anti-arrhythmic medication, which treats illnesses associated with rapid heart beats such as atrial

Atrium (anatomy)

In anatomy, the atrium , sometimes called auricle , refers to a chamber or space. For example, the term is used for a portion of the lateral ventricle in the brain and the blood collection chamber of the heart...

 and ventricular

Ventricle (heart)

In the heart, a ventricle is one of two large chambers that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. The Atria primes the Pump...

 arrhythmias.

Mechanism of action

Propafenone works by slowing the influx of sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 ions into the cardiac muscle

Cardiac muscle

Cardiac muscle is a type of involuntary striated muscle found in the walls and histologic foundation of the heart, specifically the myocardium. Cardiac muscle is one of three major types of muscle, the others being skeletal and smooth muscle...

 cells, causing a decrease in excitability of the cells.

Metabolism

Propafenone is metabolized primarily in the liver

Liver

The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...

. Because of its short half-life

Half-life

Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...

, it requires dosing two or three times daily to maintain steady blood levels. The long-term safety of propafenone is unknown. Because it is structurally similar to another anti-arrhythmic medicine, flecainide

Flecainide

Flecainide acetate is a class Ic antiarrhythmic agent used to prevent and treat tachyarrhythmias . It is used to treat a variety of cardiac arrhythmias including paroxysmal atrial fibrillation , paroxysmal supraventricular tachycardia Flecainide acetate is a class Ic antiarrhythmic agent used to...

, similar cautions should be exercised in its use. Flecainide and propafenone, like other antiarrhythmic drugs have been shown to increase the occurrence of arrhythmias (5.3% for propafenone, Teva physician prescribing information), primarily in patients with underlying heart disease. However, their use in structurally normal hearts is considered safe.

Side effects

Side effects attributed to propafenone include hypersensitivity reactions, lupus-like syndrome, agranulocytosis, CNS

Central nervous system

The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 disturbances such as dizziness, lightheadedness, gastrointestinal upset, a metallic taste and bronchospasm. About 20% of patients discontinued the drug due to side effects.

Initiation of therapy

Propafenone generally needs to be started in a hospital setting to assure ECG monitoring of the patient. There are many different dosages of propafenone, depending on clinical presentation of the arrhythmia. The treatment is generally begun with relatively high dosages (450-900mg/d) decreasing to near 300 mg/d. In most western countries the accepted maximal dosage is 900mg/d.

For economic and patient convenience reasons, some clinicians are starting certain antiarrhythmic agents in an outpatient setting for some patients. No consensus exists regarding the safety of this practice, and information is needed to determine which agents and which patients are appropriate for outpatient initiation of antiarrhythmic therapy. From a clinical point of view, this drug is used primarily in patients with relatively preserved myocardial function.
http://www.ahrq.gov/clinic/epcsums/atrialsum.htm

Contraindications and cautions

Caution should be used in administrating propafenone in individuals with hepatic dysfunction, asthma, CHF, or bradycardia.

Patent issues

The patents for the Rythmol family of products are owned by Reliant Pharmaceuticals, Inc., in Liberty Corner, N.J. Reliant acquired the patents from developer Abbott Laboratories, Inc., in 2003. Rythomol was originally developed in Europe and marketed by Knoll Pharma both in Europe and North America. The product was taken over by Abbott in 2001 when Abbott purchased Knoll.

Reliant Pharmaceuticals filed a federal patent infringement lawsuit against generic drug maker Par Pharmaceuticals, Inc., on December 19, 2006. The lawsuit, filed in the federal district court for Delaware, seeks to prevent Par from manufacturing a generic version of Rythmol. Par is seeking approval to do so from the U.S. Food and Drug Administration.

Reliant's patent for the drug was issued in October, 1997, and it expires in 2014. Par believes the patent is invalid, according to its filing with the FDA.

External links

• Rythmol (manufacturer's website)
• Propafenone (patient information)