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Generic Name:

quinidine, Oral tablet

All Brands

  • Quinora (Discontinued)
A discontinued drug is a drug that has been taken off the market due to safety issues, shortage of raw materials, or low market demand.
SECTION 1 of 4

Highlights for quinidine

Oral tablet
1

Quinidine is an oral drug that’s used to treat and prevent irregular heart rate. Quinidine sulfate can also be used to treat malaria.

2

When you first start taking quinidine or increase your dose, you’ll be monitored in a hospital or clinic. This is done so that your heart rate and heart function can be watched continuously.

3

Your dosage depends on the condition that you’re treating and the form of quinidine that you’re taking. Your doctor will decide a dose that’s right for you.

4

If you have episodes of irregular heart rate, the goal of treatment with this drug may be to increase the amount of time between episodes.

5

Common side effects include upset stomach, headaches, dizziness, and heart rate changes.

IMPORTANT INFORMATION

FDA warning

This drug has a Black Box Warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients to potentially dangerous effects.

  • Warning: This medication can increase your risk of death. Your risk may be higher if you have structural heart disease. Two analyses of evidence from studies showed that people who were taking quinidine to prevent irregular heart rate had a higher risk of dying than those who didn’t take the drug.

Irregular heart rate warning

Quinidine can cause a serious type of irregular heartbeat called Torsade de Pointes. This can be fatal.

Sick sinus syndrome warning

If you have sick sinus syndrome, quinidine can cause a very low heart rate.

Risk for other conditions

Quinidine cannot be used in people who have:

  • harmful effects from receiving an anticholinergic agent, such as people with myasthenia gravis
  • atrioventricular block in your heart
  • an idioventricular pacemaker

What is quinidine?

Quinidine is a prescription drug. It’s available in these forms: oral tablet, oral extended-release tablet, and solution for injection.

When quinidine tablets are used to treat malaria, they ‘re used in combination with quinidine gluconate injection.

Why it's used

Quinidine is used to help treat and prevent atrial fibrillation or flutter and ventricular arrhythmias, types of irregular heart rate. It’s used only after other medicines have been tried, but didn’t work to treat the condition.

Quinidine sulfate is also used to treat malaria.

How it works

Quinidine belongs to a class of drugs called antiarrhythmics. A class of drugs refers to medications that work similarly. They have a similar chemical structure and are often used to treat similar conditions.

More Details

How it works

Quinidine belongs to a class of drugs called antiarrhythmics. A class of drugs refers to medications that work similarly. They have a similar chemical structure and are often used to treat similar conditions.

Quinidine is a Class 1a antiarrhythmic. It works in the heart to slow down the electrical impulses that make the heart muscle contract and pump blood. During an arrhythmia, heart muscle contractions are irregular. Slowing down the electrical impulses can regulate the heartbeat and stop the arrhythmia.

Malaria is caused by a parasite. Quinidine works to treat malaria by stopping the parasite from growing.

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SECTION 2 of 4

quinidine Side Effects

Oral tablet

Most Common Side Effects

The most common side effects that occur with quinidine include:

  • diarrhea

  • upset stomach

  • lightheadedness

  • headache

  • tiredness

  • feeling like your heart is beating faster

  • chest pain

  • dizziness

  • skin rash

  • blurred or double vision

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious Side Effects

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life threatening, or if you think you’re experiencing a medical emergency, call 9-1-1.

  • liver damage. Symptoms may include:

    • yellowing of your skin or the whites of your eyes
  • low blood pressure. Symptoms may include:

    • dizziness
    • feeling faint
    • trouble breathing
  • autoimmune or inflammatory problems. Symptoms may include:

    • trouble breathing
    • convulsions or seizures
    • fever
    • itching
    • rashes
    • inflammation
    • muscle pain
  • cinchonism syndrome. This is more likely to happen if you use quinidine long term and have toxicity. Symptoms may include:

    • ringing in your ears
    • hearing loss
    • feeling like you’re moving when you’re not (vertigo)
    • blurred or double vision
    • confusion
  • disorders of your blood cells (blood dyscrasias). Symptoms may include:

    • fatigue
    • weakness
    • bruising
    • bleeding
  • skin reactions. Symptoms may include:

    • rash with itchy skin
    • exfoliative dermatitis
Pharmacist's Advice
Clinical Associate Professor, University of Illinois at Chicago College of Pharmacy

Quinidine doesn’t cause drowsiness.

Quinidine may make your irregular heart rate return to normal.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
SECTION 3 of 4

quinidine May Interact with Other Medications

Oral tablet

Quinidine can interact with other medications, herbs, or vitamins you might be taking. That’s why your doctor should manage all of your medications carefully. If you’re curious about how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Note: You can reduce your chances of drug interactions by having all of your prescriptions filled at the same pharmacy. That way, a pharmacist can check for possible drug interactions.

Food interactions

  • Grapefruit juice can increase the amount of quinidine in your body. Don’t drink it while you’re taking quinidine.
  • Reducing the amount of salt in your diet can increase the amount of quinidine in your body. Tell your doctor if you lower the amount of salt in your diet.

Medications that might interact with this drug

Medication to treat arrhythmia
  • amiodarone

This can increase the amount of quinidine in your body. This can lead to more side effects and toxicity.

  • digoxin
  • mexilitine
  • procainamide

Quinidine can increase the amount of these medications in your body. This can lead to more side effects and toxicity.

Antacids
  • sodium bicarbonate (Alka-Seltzer)
  • cimetidine

These medications can increase the amount of quinidine in your body. This can lead to more side effects and toxicity.

Antifungal drugs
  • ketaconazole

This medication can increase the amount of quinidine in your body. This can lead to more side effects and toxicity. 

Medicine to treat high blood pressure
  • nifedipine
  • thiazide diuretics
  • propranolol
  • diltiazem
  • verapamil

This medication can decrease the amount of quinidine in your body. This means that it may not work to treat your condition.

Anti-seizure medications
  • phenobarbital
  • phenytoin

These medications can decrease the amount of quinidine in your body. This means that it may not work to treat your condition.

Antibiotic
  • rifampin

This medication can decrease the amount of quinidine in your body. This means that it may not work to treat your condition. 

Blood thinner
  • warfarin

Quinidine can increase the amount of this medication in your body. This means that you might have more side effects or toxicity.

Medicines to treat depression
  • doxepine
  • amitriptyline
  • imipramine
  • desipramine

Quinidine can increase the amount of these medications in your body. This means that you might have more side effects or toxicity.

Antipsychotic medicines
  • haloperidol
  • phenothiazines

Quinidine can increase the amount of these medications in your body. This means that you might have more side effects or toxicity.

Pain medicines
  • codeine
  • hydrocodone

Quinidine can decrease the amount of these medicines in your body. This means that they may not work to treat your pain.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.
Quinidine warnings
heart disease
People with heart disease
  • This medication, like many other drugs that treat irregular heart rate, can increase your risk of death. There is a higher risk if you have structural heart disease.
  • If you have sick sinus syndrome, quinidine can cause a very low heart rate.
myasthenia gravis
People with myasthenia gravis

If you have this muscle condition, you shouldn’t use quinidine. Quinidine can worsen this condition.

liver problems
People with liver problems

If your liver isn’t working well, quinidine levels can increase and build up in your body. This can lead to more side effects.

pregnant women
Pregnant women

Quinidine is a category C pregnancy drug. That means two things:

  1. Research in animals has shown adverse effects to the fetus when the mother takes the drug.
  2. There haven’t been enough studies done in humans to be certain how the drug might affect the fetus.

Tell your doctor if you’re pregnant or plan to become pregnant. Quinidine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

breast-feeding
Women who are breast-feeding

Quinidine may pass through breast milk and cause serious effects in nursing child.

You and your doctor may need to decide if you’ll breastfeed or take quinidine.

children
For children

The safety and effectiveness of quinidine for irregular heart rate in people younger than 18 years old haven’t been established.

For malaria, quinidine is safe and effective in children.

Keep this drug out of the reach of children. Accidentally taking the medicine can be fatal.

contact with drug
Contact with drug

Don’t share this medicine with others even if they have the same medical condition. It can harm them.

when to call the doctor
When to call the doctor
  • Make sure to tell your doctor that you’re taking quinidine if they’re going to prescribe you another medication. This way, your doctor or pharmacist can check if the medicine is safe for you to take.
  • If you need to go to the emergency room for your heart, make sure to tell them that you’re taking quinidine. Some treatments may not work well because of quinidine. You may need to take other medicines to treat your heart problem.
allergies
Allergies

Quinidine can cause a severe allergic reaction. Symptoms may include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it, or if you developed bleeding or bruising from this medicine. Taking it again could be fatal.

SECTION 4 of 4

How to Take quinidine (Dosage)

Oral tablet

All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What are you taking this medication for?

Prevent and treat atrial fibrillation

Quinidine sulfate

Form: Oral tablet
Strengths: 200 mg and 300 mg

Quinidine sulfate

Form: Oral extended-release tablet
Strengths: 300 mg

Quinidine gluconate

Form: Oral extended-release tablet
Strengths: 324 mg
Adult Dosage (ages 18 years and older)

Quinidine sulfate oral tablet:

Treatment for irregular heart rate:

  • 200–300 mg every 6–8 hours; may be increased to 600 mg every 6 hours if needed
  • Your doctor may increase your dose after 4–5 doses.

Prevention of irregular heart rate and treatment of irregular heart rate in the ventricles:

  • 200 mg taken every 6 hours
  • Your doctor may increase your dose. The levels of quinidine in your blood may be checked.

Quinidine sulfate oral extended-release tablet:

Treatment for irregular heart rate:

  • 300–600 mg every 8–12 hours
  • Your doctor may increase your dose after 4–5 doses.

Prevention of irregular heart rate and treatment of irregular heart rate in the ventricles:

  • 300 mg taken every 8–12 hours
  • Your doctor may increase your dose.

Quinidine gluconate extended-release oral tablet:

Treatment for irregular heart rate:

  • 324–648 mg every 8–12 hours
  • Your doctor may increase your dose after 3–4 doses.
  • While your dose is being adjusted, your heart rate may increase. This doesn’t mean that quinidine isn’t working.
Child Dosage (ages 0-17 years)

The safety and effectiveness of quinidine use for atrial fibrillation in people younger than 18 years has not been established.

Special Considerations

Liver problems: If you have liver problems, your doctor may lower your dose of quinidine.

Heart problems: If you have heart failure, your doctor may lower your dose of quinidine.

 Warnings

  • When you first start taking quinidine or increase your dose, you’ll be watched in a hospital or clinic. This is done so that your heart rate and heart function can be monitored continuously with electrocardiograms. This is important if you have heart disease or other risk factors for quinidine toxicity.
  • If your heart rate increases too much or is very low or if your blood pressure is very low, quinidine may be stopped.

Malaria

Quinidine sulfate

Form: Oral tablet
Strengths: 200 mg and 300 mg

Quinidine sulfate

Form: Oral extended-release tablet
Strengths: 300 mg
Adult Dosage (ages 18 years and older)

When quinidine tablets are used to treat malaria, they’re used in combination with quinidine gluconate injection. Ask your doctor about dosing information.

Child Dosage (ages 0-17 years)

Dosage is based on your child’s age and weight.

Special Considerations

Liver problems: If you have liver problems, your doctor may lower your dose of quinidine.

Heart problems: If you have heart failure, your doctor may lower your dose of quinidine.

 Warnings

  • When you first start taking quinidine or increase your dose, you’ll be watched in a hospital or clinic. This is done so that your heart rate and heart function can be monitored continuously with electrocardiograms. This is important if you have heart disease or other risk factors for quinidine toxicity.
  • If your heart rate increases too much or is very low or if your blood pressure is very low, quinidine may be stopped.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Clinical Associate Professor, University of Illinois at Chicago College of Pharmacy

Quinidine comes with serious risks if you don't take it as prescribed.

If you don't take it at all, on schedule, or stop taking it suddenly

Your irregular heart rate could get worse and lead to fatal side effects.

If you take too much

If you take too much, you will increase your risk for dangerous side effects such as arrhythmia or liver damage.

What to do if you miss a dose

If you forget to take your dose, take it as soon as you remember. If it’s just a few hours before the time for your next dose, take only one dose at that time.

Never try to catch up by taking two doses at once. This could result in toxic side effects.

How to tell if the drug is working

You may be able to tell if this drug is working if your heart rate returns to normal or if it takes longer for your irregular heart rate to come back. Your doctor will monitor your heart rate and heart function.

If you’re taking this medication for malaria, your doctor will tell you if it’s working.

Quinidine is a long-term drug for the treatment or prevention of heart rate problems. It’s a short-term drug treatment for malaria.

Important considerations for taking quinidine

You can crush or cut quinidine sulfate tablets

You can cut quinidine sulfate extended-release tablets. You can also cut quinidine gluconate extended-release tablets. You cannot crush or chew quinidine sulfate extended-release or quinidine gluconate extended-release tablets.

Store quinidine at room temperature

Keep it from 68–77°F (20–25°C).

Keep the drug away from light and high temperature.

Keep your drugs away from areas where they could get wet, such as bathrooms. Store this drug away from moisture and damp locations.

Travel

When traveling with your medication:

  • Always carry your medication with you or in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt this medication.
  • You may need to show your pharmacy’s preprinted label to clearly identify the medication. Keep the original prescription label with you when traveling.
  • Don’t leave this drug in the car, especially when the temperature is hot or freezing.

Clinical monitoring

When you’re on quinidine, your doctor will check the following to make sure that you’re taking the correct dose and that the medicine is working:

  • kidney function
  • liver function
  • heart function, including blood pressure, heart rate, and electrocardiograms (a test that tells how well your heart is working)
  • tests to check for side effects that affect your blood cells

Are there any alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.


Show Sources

Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on July 8, 2015

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
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