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 Propafenone. If you are concerned about side effects, discuss the risks and benefits of Propafenone with your doctor.

The following side effects have been reported by at least 1% of people taking Propafenone. 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.

• bitter or metallic taste, or changes in taste
• blurred vision
• Constipation
• dizziness
• drowsiness
• Dry Mouth
• gas
• headache
• heartburn
• increased sweating
• Insomnia
• loss of appetite
• nausea
• rash
• tiredness
• upset stomach
• vomiting

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
• fast, slow, or irregular heartbeat
• joint pain
• shaking or trembling
• 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)
• swelling of feet or lower legs

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

• chest pain
• fainting
• 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 Propafenone.

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
• 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

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

• Abiraterone
• Alfuzosin
• amantadine
• Amiodarone
• antihistamines (e.g., cetirizine, doxylamine, Diphenhydramine, Hydroxyzine, Loratadine)
• antipsychotics (e.g., Chlorpromazine, Clozapine, Haloperidol, Olanzapine, Quetiapine, Risperidone)
• Aprepitant
• Aripiprazole
• "azole" antifungals (e.g., ketoconazole, fluconazole, Voriconazole)
• barbiturates (e.g., butalbital, pentobarbital, Phenobarbital)
• beta-adrenergic blockers (e.g., Metoprolol, Propranolol)
• Bicalutamide
• boceprevir
• Bosutinib
• Bupropion
• calcium channel blockers (e.g., Amlodipine, Diltiazem, Nifedipine, Verapamil)
• Celecoxib
• chloral hydrate
• chloroquine
• cincalcet
• Clobazam
• conivaptan
• Cyclosporine
• Digoxin
• Disopyramide
• dofetilide
• Domperidone
• Donepezil
• Dronedarone
• Fingolimod
• Flecainide
• formoterol
• Galantamine
• grapefruit juice
• HIV non-nucleoside reverse transcriptase inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., lopinavir, ritonavir, saquinavir, tipranavir)
• procainamide
• Indapamide
• isoniazid
• lidocaine
• lithium
• macrolide antibiotics (e.g., azithromycin, clarithromycin, erythromycin)
• Maprotiline
• Mefloquine
• Methadone
• mifepristone
• Mirabegron
• Mirtazapine
• Octreotide
• Orlistat
• Paliperidone
• peginterferon alfa-2b
• pentamidine
• Pimozide
• procainamide
• quinidine
• quinine
• quinolone antibiotics (e.g., ciprofloxacin, levofloxacin, Norfloxacin)
• rifabutin
• rifampin
• Rivastigmine
• Romidepsin
• selective serotonine reuptake inhibitors (SSRIs; Escitalopram, Fluoxetine, Paroxetine)
• serotonin antagonists (anti-emetic medications; e.g., Granisetron, Ondansetron)
• Sotalol
• sulfamethoxazole
• Tacrolimus
• telaprevir
• terbinafine
• Tetrabenazine
• Theophylline medications (e.g., Aminophylline, Oxtriphylline, theophylline)
• Ticlopidine
• Trazodone
• tricyclic antidepressants (e.g., Amitriptyline, Clomipramine, Desipramine)
• Trimethoprim
• tyrosine kinase inhibitors (e.g., Dasatinib, imatinib, Nilotinib, Sunitinib)
• Vardenafil
• 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 Propafenone. 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.

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 Propafenone.

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

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

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 should not be taken during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Propafenone, contact your doctor immediately.

Breast-feeding: Propafenone passes into breast milk. If you are a breast-feeding mother and are 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 Propafenone have not been established for children.

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