Propafenone belongs to the class of medications known as antiarrhythmics. It is used to treat certain abnormal heart rhythms. It works by slowing down the rate of nerve impulses causing the heart to beat, and by making the heart less likely to respond to abnormal impulses.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended starting dose of propafenone for adults is 150 mg taken every 8 hours. This dose may be changed by your doctor according to your particular needs. The maximum daily dose is 900 mg per day.

Propafenone should be taken with food. Swallow the tablets whole. Do not crush or chew this medication.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature and keep it out of the reach of children.

150 mg
Each white-to-off-white, biconvex, film-coated tablet, embossed with "150" on one side contains 150 mg of propafenone hydrochloride. Nonmedicinal ingredients: croscarmellose sodium, hypromellose, macrogol 400 and 6,000, magnesium stearate, pregelatinized starch, purified water, microcrystalline cellulose, and titanium dioxide.

300 mg
Each white-to-off-white, biconvex, film-coated tablet, embossed with "300" on one side contains 300 mg of propafenone hydrochloride. Nonmedicinal ingredients: croscarmellose sodium, hypromellose, macrogol 400 and 6,000, magnesium stearate, pregelatinized starch, purified water, microcrystalline cellulose, and titanium dioxide.

Do not take propafenone if you:

• are allergic to propafenone or any ingredients of the medication
• are taking the medication "ritonavir"
• have a very low heart rate (less than 50 beats per minute)
• have breathing disorders such as asthma or severe obstructive pulmonary disease
• have cardiogenic shock
• have certain types of heart rhythm disorders not managed with a pacemaker (i.e., sino-atrial, atrioventricular, and intraventricular disorders of impulse conduction and sinus node dysfunction)
• have had a heart attack in the last 3 months
• have myasthenia gravis
• have severe disorders of electrolytes (e.g., potassium) balance
• have severe liver failure
• have severe or uncontrolled congestive heart failure
• have very low blood pressure
• have been diagnosed with Brugada Syndrome (a type of heart rhythm disorder)

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• abdominal pain or cramping
• bitter or metallic taste, or changes in taste
• blurred vision
• constipation
• diarrhea
• dizziness
• drowsiness
• dry mouth
• gas
• headache
• heartburn
• increased sweating
• insomnia
• lightheadedness
• loss of appetite
• nausea
• rash
• tiredness
• vomiting
• weakness

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• abnormal muscle control and movement
• anxiety
• confusion
• dizziness when rising from a sitting or lying position
• fainting
• fast, slow, or irregular heartbeat
• hallucinations (seeing or hearing things that aren’t there)
• joint pain
• shaking or trembling
• shortness of breath
• signs of clotting problems (e.g., unusual nosebleeds, bruising, blood in urine, coughing blood, bleeding gums, cuts that don't stop bleeding)
• signs of decreased heart function (e.g., shortness of breath, swelling of feet or lower legs, unusual tiredness or weakness)
• signs of liver problems (e.g., nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or whites of the eyes, dark urine, pale stools)
• sudden skin eruptions of small red bumps with fever or rash
• swelling of feet or lower legs

Stop taking the medication and seek immediate medical attention if any of the following occur:

• chest pain
• seizures
• signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abnormal heart rhythms: Certain medications used to treat abnormal heart rhythms, including propafenone, may cause new abnormal heart rhythms or worsen existing ones. Your doctor will monitor you closely while you are taking propafenone. If you experience a fast, slow, or irregular heartbeat; fainting; heart palpitations; or dizziness while taking this medication, contact your doctor immediately.

Asthma or bronchitis: Propafenone can worsen breathing problems for people with asthma or bronchitis. If you have asthma or other breathing disorders, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Drowsiness/reduced alertness: Propafenone may cause blurred vision, dizziness, and fatigue. Do not drive or operate machinery until you know how this medication affects you.

Heart failure: Propafenone can cause or worsen heart failure and should not be used by people with severe or untreated heart failure. If you have heart failure and are taking this medication, your doctor will monitor you closely during treatment. If you notice shortness of breath; weight gain; or swelling in the hands, feet, or lower legs while taking propafenone, contact your doctor immediately.

If you have a heart condition, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Infection: Propafenone can reduce the number of cells that fight infection in the body (white blood cells). This usually occurs within 4 to 6 weeks of starting this medication. If you experience fever, sore throat, fatigue, weakness, or a general feeling of being unwell while taking propafenone, contact your doctor immediately.

Kidney function: Kidney disease or reduced kidney function may cause this medication to build up in the body, causing side effects. If you have reduced kidney function or kidney disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: The liver removes most of this medication from the body. Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. Your doctor may want to test your liver function regularly with blood tests while you are taking this medication.

If you experience symptoms of liver problems such as fatigue, feeling unwell, loss of appetite, nausea, yellowing of the skin or whites of the eyes, dark urine, pale stools, abdominal pain or swelling, and itchy skin, contact your doctor immediately.

Pregnancy: Propafenone crosses the placenta and may affect the developing baby if it is taken during pregnancy. This medication should not be taken during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are breast-feeding and taking propafenone, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

Seniors: Seniors may experience more dizziness while taking propafenone and may require lower doses.

There may be an interaction between propafenone and any of the following:

• abiraterone
• aliskiren
• alpha-agonists (e.g., clonidine, guanfacine)
• antiarrhythmics (e.g., amiodarone, disopyramide, dronedarone, flecainide, procainamide, sotalol)
• anticancer medications (e.g., doxorubicin, etoposide, vincristine)
• antipsychotics (e.g., chlorpromazine, clozapine, haloperidol, olanzapine, quetiapine, risperidone)
• "azole" antifungals (e.g., ketoconazole, fluconazole, voriconazole)
• apalutamide
• beta-adrenergic blockers (e.g., atenolol, metoprolol, propranolol)
• bilastine
• bupropion
• calcium channel blockers (e.g., diltiazem, verapamil)
• cinacalcet
• cobicistat
• colchicine
• cyclosporine
• dabigatran
• darifenacin
• digoxin
• domperidone
• donepezil
• doxepin
• duloxetine
• edoxaban
• enzalutamide
• everolimus
• fentanyl
• galantamine
• general anaesthetics (medications to put you to sleep for surgery)
• glecaprevir and pibrentasvir
• grapefruit juice
• HIV protease inhibitors (e.g., atazanavir, fosamprenavir, lopinavir, ritonavir, tipranavir)
• inotuzumab
• ivabradine
• lumacaftor and ivacaftor
• macrolide antibiotics (e.g., azithromycin, clarithromycin, erythromycin)
• methadone
• mifepristone
• mirabegron
• morphine
• naloxegol
• neostigmine
• nirmatrelvir and ritonavir
• ondansetron
• orlistat
• peginterferon alfa-2b
• pyridostigmine
• quinolone antibiotics (e.g., levofloxacin, moxifloxacin)
• ranolazine
• rifampin
• rivastigmine
• seizure medications (e.g., carbamazepine, lacosamide, phenobarbital, phenytoin, primidone)
• selective serotonin reuptake inhibitors (SSRIs; citalopram, escitalopram, fluoxetine, paroxetine)
• sirolimus
• somatostatin-like medications (e.g., lanreotide, octreotide, pasireotide)
• sphingosine 1-phosphate (S1P) receptor inhibitors (e.g., fingolimod, ponesimod, siponimod)
• tacrolimus
• tenofovir
• terbinafine
• terbutaline
• theophylline medications (e.g., aminophylline, theophylline)
• tizanidine
• tricyclic antidepressants (e.g., clomipramine, desipramine)
• tyrosine kinase inhibitors (e.g., dasatinib, nilotinib, sunitinib, tofacitinib)
• ubrogepant
• venlafaxine
• warfarin

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.