What is Propafenone ER: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Propafenone ER overview

BRAND NAMES:

  • Rythmol SR, Rythmol SR

Generic Names:

  • Propafenone Hcl Er

Uses:

  • Treats or prevents atrial fibrillation (heart rhythm problems or arrhythmias).

Therapeutic Classes:

  • Antiarrhythmic, Group IC

Forms:

  • Long Acting Capsule, Tablet

How it’s taken:

  • By mouth

What is Propafenone ER used for?

What form(s) does Propafenone ER come in

  • Long Acting Capsule

  • Tablet

What are common Propafenone ER doses?

  • Capsule 225mg

  • Capsule 325mg

  • Capsule 425mg

  • Capsule Extended Release 12 Hour 225MG

  • Capsule Extended Release 12 Hour 325MG

Common Propafenone ER prescriptions

  • Propafenone HCl ER
    225mg capsule

  • Propafenone HCl ER
    325mg capsule

  • Propafenone HCl ER
    425mg capsule

  • Propafenone HCl ER
    225mg capsule extended release 12 hour

  • Propafenone HCl ER
    325mg capsule extended release 12 hour

  • Propafenone HCl ER
    425mg capsule extended release 12 hour

How to take Propafenone ER

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

  • You may need to carry identification stating that you are using propafenone. Ask your doctor about this.

  • Swallow the extended-release capsule whole. Do not crush, break, or chew it.

  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.

  • Swallow the extended-release capsule whole. Do not crush, break, or chew it.

  • You may need to carry identification stating that you are using propafenone. Ask your doctor about this.

  • Take your medicine as directed. Your dose may need to be changed several times to find what works best for you.

  • Read and follow the patient instructions that come with this medicine. Talk to your doctor or pharmacist if you have any questions.

What to do if you miss a dose of Propafenone ER

  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

  • Oral routeAsk your pharmacist, doctor, or health caregiver about the best way to dispose of any outdated medicine or medicine no longer needed.

  • Take a dose as soon as you remember. If it is almost time for your next dose, wait until then and take a regular dose. Do not take extra medicine to make up for a missed dose.

Propafenone ER contraindications

  • Do not use this medicine if you have had an allergic reaction to propafenone. Your doctor will determine if this medicine is right for you, because this medicine should not be used if you have certain heart or heart rhythm problems, such as Brugada syndrome, heart failure, AV block, or sick sinus syndrome (unless you have an artificial pacemaker). Do not use this medicine if you have very low blood pressure, mineral imbalance (such as low salt levels in your blood), or lung disease (such as severe COPD).

Propafenone ER warnings

  • Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments. You might need to have an electrocardiogram (ECG) or a blood test for your ANA level (antinuclear antibody).

  • Unusual bleeding, bruising, or weakness

  • This medicine may make you dizzy or drowsy. Avoid driving, using machines, or doing anything else that could be dangerous until you know how this medicine affects you.

  • Make sure your doctor knows if you are pregnant or breastfeeding, or if you have kidney disease, liver disease, myasthenia gravis, lupus, or breathing problems. Tell your doctor if you have heart disease or have recently had a heart attack. Make sure your doctor knows if you have a pacemaker.

  • This medicine affects your heart rhythm, so it could cause new or worse rhythm problems. Call your doctor if your symptoms do not improve or if they get worse.

  • This medicine can lower the number of white blood cells you have, so you might be more likely to get an infection. If you can, avoid people who are sick. Check with your doctor if you have a fever, chills, cough, or sore throat.

  • Call your doctor if you have severe diarrhea, vomiting, sweating, loss of appetite, or thirst. These problems can change the mineral levels in your blood and lead to side effects from this medicine.

  • This medicine may decrease the amount of sperm men make. Talk to your doctor if you have concerns about this.

Propafenone ER interactions

  • There are many other drugs that can interact with propafenone. Make sure your doctor knows about all other medicines you are using, especially digoxin (Lanoxin®), ketoconazole (Nizoral®), ritonavir (Norvir®), saquinavir (Fortovase®, Invirase®), other medicines for heart rhythm problem (such as amiodarone, disopyramide, dofetilide, lidocaine, quinidine, Cardioquin®, Cordarone®, Norpace®, Quinaglute®, Tikosyn®), blood pressure medicine (such as atenolol, metoprolol, propranolol, Tenormin®), or a blood thinner (such as warfarin, Coumadin®, Jantoven®).

  • Make sure your doctor knows if you are also using cimetidine (Tagamet®), rifampin (Rifadin®, Rimactane®), or orlistat (Xenical®). Tell your doctor if you use certain antibiotics (such as azithromycin, clarithromycin, erythromycin, Zithromax®), medicine for depression (such as amitriptyline, desipramine, nortriptyline, paroxetine, sertraline, Elavil®), or medicine for mental illness (such as prochlorperazine, promethazine, Compazine®, Phenergan®, Mellaril®, Trilafon®).

  • Tell your doctor if you smoke.

  • Do not eat grapefruit or drink grapefruit juice while you are using this medicine.

  • This medicine may decrease the amount of sperm men make. Talk to your doctor if you have concerns about this.

  • This medicine may make you dizzy or drowsy. Avoid driving, using machines, or doing anything else that could be dangerous until you know how this medicine affects you.

  • Your doctor will check your progress and the effects of this medicine at regular visits. Keep all appointments. You might need to have an electrocardiogram (ECG) or a blood test for your ANA level (antinuclear antibody).

Propafenone ER side effects

Serious Side Effects

  • Swelling in your hands, ankles, or feet, weight gain

  • Unusual bleeding, bruising, or weakness

  • Trouble breathing, cold sweat, bluish-colored skin

  • Fever, chills, cough, stuffy or runny nose, sore throat, and body aches

  • Chest pain, or worsening of heart rhythm problem

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

  • Lightheadedness, dizziness, or fainting

  • Unexpected heartbeat changes, fast or slow heartbeat

Less Serious Side Effects

  • Nausea, constipation

  • Anxiety

  • Metallic or bitter taste

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