Taking antiarrhythmic drugs, including quinidine, may increase the risk of death. Tell your doctor if you have heart disease such as a valve problem or heart failure (HF; condition in which the heart cannot pump enough blood to other parts of the body). If you experience any of the following symptoms, call your doctor immediately: irregular heartbeat or chest pain.
Quinidine may increase the chance of having arrhythmias (irregular heartbeats) and has not been proven to help people without life-threatening arrhythmias to live longer.
Talk to your doctor about the risks of taking quinidine.
Why is this medicine prescribed?
Quinidine is used to treat certain types of irregular heartbeats. It is also used to treat malaria (a serious or life-threatening illness that is spread by mosquitos in certain parts of the world). Quinidine is in a class of medications called antiarrhythmic medications. It works by making your heart more resistant to abnormal activity. It also works by killing the organisms that cause malaria.
Are there other uses for this medicine?
Talk to your doctor about the risks of using this medication for your condition.
How should this medicine be used?
Quinidine comes as an immediate-release tablet and an extended-release (long-acting) tablet to take by mouth. Quinidine tablets are taken every 6 hours. Extended-release tablets are taken every 8 or 12 hours. Take quinidine at around the same times every day.
Take quinidine exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
The extended-release tablet may be split in half. Swallow the whole or half tablets whole; do not chew or crush them.
Quinidine helps control your condition but will not cure it. Continue to take quinidine even if you feel well. Do not stop taking quinidine without talking to your doctor.
What special precautions should I follow?
Before taking quinidine,
- tell your doctor or pharmacist if you are allergic to this medication, any part of this medication, or any other medications, foods or substances. Tell your doctor or pharmacist about the allergy and what symptoms you had.
- tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and nutrition supplements you are taking or plan to take while taking quinidine. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
- the following nonprescription products may interact with quinidine: cimetidine and sodium bicarbonate. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking quinidine. Do not start any of these medications while taking quinidine without discussing with your healthcare provider.
- tell your doctor if you have heart block (condition in which electrical signals are not passed normally from the upper chambers of the heart to the lower chambers) or myasthenia gravis (a disorder of the nervous system that causes muscle weakness). Also tell your doctor if you have ever had a serious reaction, especially a bleeding problem or problems with your blood after taking medication in the past. Your doctor may tell you not to take quinidine.
- tell your doctor if you have or have ever had a prolonged QT interval (condition that increases the risk of developing an irregular heartbeat that may cause fainting or sudden death); a slow heartbeat; low blood levels of calcium, magnesium or potassium in your blood; or liver or kidney disease.
- tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking quinidine, call your doctor.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking quinidine.
What special dietary instructions should I follow?
Do not eat large amount of grapefruit or drink grapefruit juice while taking this medication. Do not change the amount of salt in your diet without talking to your doctor.
What should I do if I forget to take a dose?
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
What should I do in case of overdose?
In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help . If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.
Symptoms of overdose may include:
- irregular heartbeat
- diarrhea
- vomiting
- headache
- ringing in the ears or loss of hearing
- vision changes (blurred vision or light sensitivity)
- confusion
What side effects can this medicine cause?
Quinidine may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
- diarrhea
- nausea
- vomiting
- heartburn
- fever
- dizziness
- lightheadedness
- headache
- fatigue
- weakness
- rash
- difficulty sleeping
- tremor
Some side effects can be serious. If you experience any of the following symptoms or those listed in the IMPORTANT WARNINGS section, call your doctor immediately or get emergency medical treatment:
- ringing in the ears or loss of hearing, vision changes (blurred vision or light sensitivity), dizziness, confusion
- unusual bleeding or bruising
- loss of appetite, nausea, yellow eyes or skin, pain in the upper right area of the stomach, or dark urine
- seizures
- rash; hives; itching; or swelling of the face, throat, lips, or eyes
Quinidine may cause other side effects. Call your doctor if you have any unusual problems while receiving this medication.
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online ( https://www.fda.gov/Safety/MedWatch ) or by phone ( 1-800-332-1088).What should I know about storage and disposal of this medication?
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).
Keep all medication out of sight and reach of children as many containers are not child-resistant. Always lock safety caps. Place the medication in a safe location – one that is up and away and out of their sight and reach. https://www.upandaway.org Dispose of unneeded medications in a way so that pets, children, and other people cannot take them. Do not flush this medication down the toilet. Use a medicine take-back program. Talk to your pharmacist about take-back programs in your community. Visit the FDA's Safe Disposal of Medicines website https://goo.gl/c4Rm4p for more information.What other information should I know?
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your body's response to quinidine.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
Keep a written list of all of the prescription and nonprescription (over-the-counter) medicines, vitamins, minerals, and dietary supplements you are taking. Bring this list with you each time you visit a doctor or if you are admitted to the hospital. You should carry the list with you in case of emergencies.