Propafenone: Formula, Presentation, Indications, Mechanism of Action, Dosage, Side Effects and Interactions

It is an antiarrhythmic drug for use in patients with life-threatening ventricular arrhythmias, such as ventricular tachycardia.

It is also effective in preventing the recurrence of atrial fibrillation and supraventricular tachycardia once a normal sinus rhythm has been restored .

Chemical formula

  • C21H27NO3.

Presentation

  • 150 mg and 225 mg tablets

Indications

Propafenone is indicated for:

Conversion and maintenance of sinus rhythm in patients with supra-ventricular arrhythmias:

  • Conversion to sinus rhythm in patients with recent onset of fibrillation .
  • Maintenance of sinus rhythm in patients with refractory paroxysmal or atrial fibrillation.
  • For paroxysmal supraventricular tachycardia, treatment in patients with atrioventricular reentrant tachycardia, including those patients with Wolff Parkinson White syndrome.
  • Treat documented ventricular arrhythmias, such as sustained ventricular tachycardia.

Mechanism of action

The mechanism of action of Propafenone is to inhibit the rapid sodium channels of the myocardial cell membrane, reducing the speed of transmission of the nerve impulse.

Dosage

  • The dose should be assessed individually depending on the patient’s response and tolerance.
  • Therapy should be started with 150 mg administered every eight hours (450 mg per day).
  • The dose can be increased in intervals of 3 to 4 days to 225 mg every 8 hours (675 mg per day).
  • If an additional therapeutic effect is necessary, the dose can be increased to 300 mg every 8 hours (900 mg per day).
  • There are no investigations where utility and safety can be established in doses higher than 900 mg per day.
  • When prolonged-release capsules are used, the initial dose should be 225 mg every 12 hours.
  • The dose can be increased in intervals of 5 days at least 325 mg every 12 hours, if necessary, to 425 mg every 12 hours.
  • In patients with hepatic impairment the dose should be reduced.

Side effects

Due to its beta-blocking activity, propafenone should be used with caution in patients with weak cardiac muscle.

Like congestive heart failure, in slow heart rate, any form of blockage of the electrical conduction of the heart, low blood pressure or asthma .

The most serious side effect of propafenone is that it causes irregular heart arrhythmias or life-threatening ventricular arrhythmias or heart block.

The common side effects that have been reported with the use of propafenone are:

  • Dizziness
  • Sickness.
  • Persistent vomiting
  • Blurry vision.
  • Anorexia.
  • Unusual taste
  • Fatigue.
  • Constipation .
  • Headache.
  • Reduction of cardiac conduction.
  • Abdominal pain.
  • Chest pain.
  • Heart palpitations.
  • Accelerated heart rate.
  • Abnormal heartbeat.
  • Aggravation of myasthenia gravis.
  • Increase in the death rate.
  • Congestive heart failure.
  • Difficult breathing
  • Swelling of the face, lips, tongue and throat.
  • Feeling short of breath
  • Rapid weight gain
  • Fever, chills, sore throat, flu symptoms, weakness.
  • Confusion, thoughts or unusual behavior.
  • Convulsions
  • Slow, weak heart rhythm
  • Yellow eyes and skin.
  • Abnormal dreams
  • Abnormal speech
  • Memory loss.
  • Numbness.
  • Psychosis and mania

Warnings and contraindications

Do not administer in case of allergy to the components.

Special caution should be exercised, in case the patient presents respiratory problems such as:

  • Asthma , chronic bronchitis, emphysema , kidney problems, liver problems, myasthenia gravis, hereditary disorders of heart disease (Brugada syndrome), heart problems such as heart failure , slow heartbeat.
  • Propafenone can affect heart rhythm (prolongation of the QT interval), causing rapid, irregular heartbeat, although rarely fatal.
  • Other symptoms such as severe dizziness, fainting, which require immediate medical attention.
  • The consumption of alcoholic beverages must be limited.
  • The doctor should be informed, in case of surgical interventions that this medication is being used.
  • This medicine should not be administered during pregnancy or during breastfeeding.
  • The doctor must establish if the benefits are greater than the risks, to recommend their use in these conditions.
  • You should avoid eating or drinking grapefruit (grapefruit) while using this medication, as its consumption increases the possibility of the appearance of side effects.

Drug interactions

Interactions with other medications can change how they work or increase the risk of serious side effects.

Concomitant medications such as Quinidine and Prozac should not be used concomitantly since they inhibit the metabolism of propafenone.

Dosage of medications such as: Digoxin (Lanoxin), warfarin (Coumadin) and beta blockers, for example metoprolol Lopressor, Toprol XL, Propranolol Inderal, InnoPran, interact with Propafenone by increasing its levels.

Therefore, it may be necessary to reduce the doses of these drugs if they are administered together with Propafenone.

Rifampin increases the metabolism of propafenone, decreasing the levels of propafenone in the blood.

Orlistat (Xenical) can reduce the absorption of propafenone. The suspension of treatment with orlistat in patients stabilized with propafenone, can cause propafenone toxicity, because more propafenone will be absorbed after this suspension.

Propafenone can alter the rhythm of pacemakers and defibrillators. These devices must be reprogrammed and monitored very carefully.

Safety and efficacy in children and pregnant women has not yet been established.

Propafenone is excreted in breast milk. Mothers must decide whether to stop breastfeeding or stop propafenone.