Propafenone

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Propafenone belongs to a group of medicines called anti-arrhythmic agents. Antiarrhythmic medications are used to treat illnesses associated with rapid heart beats such as atrial and ventricular arrhythmias.

Propafenone is used to treat life-threatening ventricular heart rhythm disorders. Propafenone is also used to increase the amount of time between having symptoms of heart rhythm disorders called atrial fibrillation (AF) or paroxysmal supraventricular tachycardia (PSVT).

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[edit] BRAND NAMES

[edit] STRUCTURE

Propafenone.jpg

[edit] MECHANISM OF ACTION

Propafenone is a Class 1C antiarrhythmic drug with local anesthetic effects and a direct stabilizing action on myocardial membranes.

Propafenone works by slowing the influx of sodium into the heart muscle cells, causing a decreases in the speed of electrical conduction.

The electrophysiological effect of propafenone manifests itself in a reduction of phase 0 depolarization (decreasing Vmax). In Purkinje fibers, and to a lesser extent myocardial fibers, propafenone reduces the the influx of sodium into the cells. Diastolic excitability threshold is increased and effective refractory period prolonged.

Propafenone has mild beta blocking properties as well. In clinical trials, resting heart rate decreases of about 8% at the higher end of the therapeutic plasma concentration range.

[edit] INDICATIONS

Propafenone is indicated to:

  • Reduce the recurrence of atrial fibrillation in patients in patients with episodic (most likely paroxysmal* or persistent) atrial fibrillation who do not have structural heart disease (It is not recommended for patients with coronary artery disease). Atrial fibrillation is the most common supraventricular tachycardia (SVT) and is a main cause of stroke, especially among elderly people. Atrial fibrillation produces a rapid and irregular heartbeat, during which the atria (the upper two chambers of the heart that receive blood) quiver, or fibrillate, instead of beating normally.

*"Paroxysmal" means from time to time

  • Reduce the recurrence of paroxysmal supraventricular tachycardia (PSVT) associated with disabling symptoms in patients who do not have structural heart disease (It is not recommended for patients with coronary artery disease). PSVT may occur at any age and commonly occurs in patients who have no other types of heart disease. Patients with PSVT typically describe a rapid, or racing, regular heartbeat (between 130 and 230 beats per minute) that starts and stops abruptly.
  • Treat documented life-threatening ventricular arrhythmias.


Usage Considerations:

  • Use in patients with permanent atrial fibrillation or with atrial flutter or PSVT has not been evaluated. Do not use to control ventricular rate during atrial fibrillation.
  • In patients with atrial fibrillation and atrial flutter, use RYTHMOL with drugs that increase the atrioventricular nodal refractory period.
  • Because of proarrhythmic effects, use with lesser ventricular arrhythmias is not recommended, even if patients are symptomatic.
  • The effect of propafenone on mortality has not been determined

[edit] DOSAGE

Because of the short half-life (3-6 hours) propafenone must be taken two to three times daily to ensure a constant level.

  • Initiate therapy with 150 mg given every 8 hours.
  • As needed, uptitrate in 3 to 4 days to 225 to 300 mg every 8 hours.
  • Consider reducing the dose in patients with hepatic impairment, significant widening of the QRS complex, or second- or third-degree AV block

[edit] CONTRAINDICATIONS

  • Heart failure (weak heart), cardiogenic shock
  • A heart rate that is too slow (Sinoatrial, atrioventricular, and intraventricular disorders of impulse generation or conduction) in the absence of pacemaker
  • Known Brugada Syndrome
  • Bradycardia
  • Bronchospastic disorders ( breathing problems, asthma) and severe obstructive pulmonary disease
  • Marked electrolyte imbalance
  • Marked hypotension

[edit] WARNINGS AND PRECAUTIONS

  • May cause new or worsened arrhythmias. Evaluate patients via ECG prior to and during therapy.
  • Propafenone may unmask Brugada or Brugada-like Syndrome.
  • Avoid use with other drugs that prolong the QT interval.
  • Avoid simultaneous use of propafenone with both a cytochrome P450 2D6 inhibitor and a 3A4 inhibitor.
  • May provoke overt heart failure.
  • May cause dose-related first-degree AV block or other conduction disturbances. Only use in patients with conduction disorders who have pacemakers.
  • May affect artificial pacemakers. Monitor pacemaker function.
  • Agranulocytosis: Patients should report signs of infection.
  • May exacerbate myasthenia gravis

[edit] INTERACTIONS

  • Propafenone is metabolized by CYP2D6, CYP3A4, and CYP1A2 isoenzymes. Inhibitors of CYP2D6 (such as desipramine, paroxetine, ritonavir, or sertraline), CYP1A2 (such as amiodarone and tobacco smoke), and CYP3A4 (such as ketoconazole, ritonavir, saquinavir, erythromycin, or grapefruit juice) increase propafenone exposure.
  • Propafenone may increase digoxin or warfarin levels.
  • Orlistat may reduce propafenone exposure. In postmarketing reports, abrupt cessation of orlistat in patients stabilized on propafenone has resulted in severe adverse events including convulsions, atrioventricular block, and acute circulatory failure. Taper orlistat withdrawal.
  • Amiodarone: Concomitant administration of propafenone and amiodarone can affect conduction and repolarization and is not recommended.
  • Lidocaine: concomitant use of propafenone and lidocaine has been reported to increase the risks of central nervous system side effects of lidocaine

[edit] PREGNANCY AND LACTATION

  • Pregnancy Category C (US). There are no adequate and well-controlled studies in pregnant women. Propafenone should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
  • Nursing Mothers: Propafenone is excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from propafenone, decide whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

[edit] SIDE EFFECTS

The most commonly reported adverse events with propafenone (>5%) included: altered taste (metallic taste), nausea and/or vomiting, dizziness, constipation, headache, fatigue, first-degree AV block, and intraventricular conduction delay.

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