Molecule

Drug Groups

approved

Description

An antiarrhythmia agent that is particularly effective in ventricular arrhythmias. It also has weak beta-blocking activity. The drug is generally well tolerated. [PubChem]

Indication

Used to prolong the time to recurrence of paroxysmal atrial fibrillation/flutter (PAF) associated with disabling symptoms in patients without structural heart disease. Also used for the treatment of life-threatening documented ventricular arrhythmias, such as sustained ventricular tachycardia.

Pharmacology

Propafenone is a Class 1C antiarrhythmic drug with local anesthetic effects, and a direct stabilizing action on myocardial membranes. It is used in the treatment of atrial and ventricular arrhythmias. It works by slowing the influx of sodium ions into the cardiac muscle cells, causing a decrease in excitablity of the cells. Propafenone has local anesthetic activity approximately equal to procaine.

Toxicity

Symptoms of propafenone overdose (usually most severe within the first 3 hours) may include convulsions (rarely), heartbeat irregularities, low blood pressure, and sleepiness.

Affected Organisms

Biotransformation

Metabolized primarily in the liver where it is rapidly and extensively metabolized to two active metabolites, 5-hydroxypropafenone and N-depropylpropafenone. These metabolites have antiarrhythmic activity comparable to propafenone but are present in concentrations less than 25% of propafenone concentrations.

Absorption

Nearly completely absorbed following oral administration (90%). Systemic bioavailability ranges from 5 to 50%, due to significant first-pass metabolism. This wide range in systemic bioavailability is related to two factors: presence of food (food increases bioavailability) and dosage (bioavailability is 3.4% for a 150-mg tablet compared to 10.6% for a 300-mg tablet).

Half Life

2-10 hours

Protein Binding

97%

Elimination

Approximately 50% of propafenone metabolites are excreted in the urine following administration of immediate release tablets.

Distribution

* 252 L

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