Reviewed on 9/23/2021

What Is Propafenone and How Does It Work?

Propafenone is used to treat certain types of serious (possibly fatal) irregular heartbeat (such as paroxysmal supraventricular tachycardia and atrial fibrillation). It is used to restore normal heart rhythm and maintain a regular, steady heartbeat. Propafenone is known as an anti-arrhythmic drug. It works by blocking the activity of certain electrical signals in the heart that can cause an irregular heartbeat. Treating an irregular heartbeat can decrease the risk for blood clots, and this effect can reduce your risk of heart attack or stroke.

Propafenone is available under the following different brand names: Rythmol and Rythmol SR.

What Are the Dosages of Propafenone?

Adult Dosage Forms and Strengths

Capsule: Schedule V

  • 150 mg
  • 225 mg
  • 300 mg

Capsule, extended-release

  • 225 mg
  • 325 mg
  • 425 mg

Dosage Considerations – Should be Given as Follows:

Ventricular Arrhythmias/Paroxysmal Supraventricular Tachycardia

  • Immediate release (IR): 150 mg orally every 8 hours; may increase to 225 mg every 8 hours after 3-4 days, and, if required, 300 mg every 8 hours; not to exceed 300 mg every 8 hours

Atrial Fibrillation/Flutter

  • Immediate release (IR): 150 mg orally every 8 hours; may increase to 225 mg every 8 hours after 3-4 days, and, if required, 300 mg every 8 hours; not to exceed 300 mg every 8 hours
  • Extended-release (ER): 225 mg orally every 12 hours initially; may increase the dose every 5 days to 325 mg orally every 12 hours OR 425 mg orally every 12 hours, if necessary

Dosing Considerations

  • Reduce dose in patients with the significant widening of the QRS complex or 2nd or 3rd degree AV block

Dosing Modifications

  • Renal impairment: Not studied
  • Hepatic impairment: Administer 20-30% of normal IR dose and monitor closely; consider a dose reduction if administering ER dose
  • Pediatric: Safety and efficacy not established


Heart Disease: Causes of a Heart Attack See Slideshow

What Are Side Effects Associated with Using Propafenone?

Common side effects of Propafenone include:

  • Unusual/metallic/salty/unpleasant taste
  • Dizziness
  • Lightheadedness
  • Nausea
  • Vomiting
  • Constipation
  • Headache
  • Intraventricular conduction delay
  • Fatigue
  • Blurred vision
  • Weakness
  • Shortness of breath
  • Fast heart rate
  • Sow heart rate
  • Palpitations
  • Tremor
  • Loss of appetite
  • Diarrhea
  • Loss of control of bodily movements
  • Loss of balance or coordination
  • 1°AV block
  • Chest pain (angina)
  • Congestive heart failure (CHF)
  • Atrial fibrillation
  • Bundle branch block
  • 2nd degree AV block
  • Low blood pressure (hypotension)
  • Sinus arrest
  • Anxiety
  • Tiredness
  • Ringing in your ears
  • Unusual dreams
  • Flushing (warmth, redness, or tingly feeling under your skin)

Other side effects of propafenone include:

Postmarketing side effects of propafenone reported include:

This is not a complete list of side effects and other serious side effects may occur. Call your doctor for information and medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Propafenone?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Severe interactions of propafenone include:
    • dofetilide
    • tipranavir
  • Propafenone has serious interactions with at least 27 different drugs.
  • Propafenone has moderate interactions with at least 131 different drugs.
  • Propafenone has mild interactions with at least 90 different drugs.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Propafenone?


  • NHLBI's Cardiac Arrhythmia Suppression Trial (CAST): Excessive mortality or nonfatal cardiac arrest (7.7%) shown with encainide or flecainide, compared with placebo (3%)
  • Applicability of CAST results to other populations (e.g., patients without recent MI) is uncertain; therefore, reserve use of class IC antiarrhythmics for life-threatening ventricular arrhythmias.
  • Considering the known proarrhythmic properties of propafenone and the lack of evidence of improved survival for any antiarrhythmic drug in patients without life-threatening arrhythmias, use should be reserved for patients with life-threatening ventricular arrhythmias.
  • This medication contains propafenone. Do not take Rythmol or Rythmol SR if you are allergic to propafenone or any ingredients contained in this drug.
  • Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


Effects of Drug Abuse

  • No information available

Short-Term Effects

  • Agranulocytosis was reported (most within the first 2 months of treatment).
  • See "What Are Side Effects Associated with Using Propafenone?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Propafenone?"


  • May alter pacemaker thresholds.
  • Elevated ANA titers reported with use; may consider discontinuing therapy in symptomatic patients with positive ANA titers.
  • Use caution in patients with hematologic disorders, myasthenia gravis (may exacerbate the condition), hepatic/renal impairment.
  • Use caution in patients with hypersensitivity to propranolol.
  • There is a potential for increased mortality post-heart attack (myocardial infarction [MI]), as with encainide and flecainide (other class ICs).
  • May cause life-threatening drug-induced arrhythmias including asystole, ventricular fibrillation, ventricular tachycardia, and torsade de pointes.
  • Through CYP3A inhibition, grapefruit juice consumption may decrease elimination (i.e. increase serum levels).
  • Correct electrolyte imbalance, especially hypomagnesemia or hypokalemia before initiating therapy and throughout.
  • Plasma concentration has a poor correlation to the antiarrhythmic effect.
  • New or worsening heart failure may occur.
  • Slows AV conduction and may cause AV block.
  • Brugada syndrome may be unmasked after exposure to propafenone; perform ECG after initiation and discontinue the drug if changes are suggestive of Brugada Syndrome.
  • Agranulocytosis was reported (most within the first 2 months of treatment).
  • Highly metabolized by the liver; severe liver impairment increases bioavailability by 70%.

Pregnancy and Lactation

  • Use propafenone with caution during pregnancy if the benefits outweigh the risks. Animal studies show risk and human studies are not available or neither animal nor human studies were done.
  • Propafenone crosses into breast milk; discontinue the drug or do not a nurse.


Atrial fibrillation is a(n) ... See Answer

Medscape. Propafenone.
RxList. Rythmol.

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