Highlights for quinidine

  1. Quinidine oral tablet is only available as a generic drug. There is no brand-name version available.
  2. Quinidine comes as an immediate-release oral tablet, an extended-release oral tablet, and a solution for injection.
  3. Quinidine is used to treat and prevent irregular heart rate. Quinidine sulfate can also be used to treat malaria.

Important warnings

FDA Warning: Increased risk of death

  • 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 about drug effects that may be dangerous.
  • Quinidine 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.

Other warnings

  • 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 can not be used in people who have myasthenia gravis, complete atrioventricular block in their heart, or a junctional or idioventricular pacemaker. Quinidine is also not safe for you if your doctor has told you that an anticholinergic drug would not be safe.

What is quinidine?

Quinidine is a prescription drug. It comes as an oral tablet, an oral extended-release tablet, and a solution for injection.

When quinidine tablets are used to treat malaria, they‘re used after initial treatment with the 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 medications have been tried, but didn’t work to treat the condition.

Quinidine sulfate is also used to treat malaria.

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.

How it works

Quinidine belongs to a class of drugs called antiarrhythmics. A class of drugs is a group of medications that work in a similar way. These drugs 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.

Quinidine side effects

Quinidine oral tablet doesn’t cause drowsiness, but it can cause other side effects.

More common side effects

The more 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

Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • 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

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.

Quinidine may interact with other medications

Quinidine oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with quinidine are listed below.

Arrhythmia medications

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

Taking other arrhythmia drugs with quinidine can increase the amount of these medications in your body. This can lead to more side effects and toxicity. Examples of these drugs include:

  • digoxin
  • mexiletine
  • procainamide

Antacids

Taking these medications with quinidine can increase the amount of quinidine in your body. This can lead to more side effects and toxicity. Examples of these drugs include:

  • sodium bicarbonate (Alka-Seltzer)
  • cimetidine

Antifungal drug

Taking ketoconazole with quinidine can increase the amount of quinidine in your body. This can lead to more side effects.

High blood pressure medications

Taking these drugs with quinidine can decrease the amount of quinidine in your body. This means that it may not work to treat your condition. Examples of these drugs include:

  • nifedipine
  • thiazide diuretics
  • propranolol
  • diltiazem
  • verapamil

Anti-seizure medications

Taking these drugs with quinidine can decrease the amount of quinidine in your body. This means that it may not work to treat your condition. Examples of these drugs include:

  • phenobarbital
  • phenytoin

Antibiotic

Taking rifampin with quinidine can decrease the amount of quinidine in your body. This means it may not work to treat your condition.

Blood thinner

Taking warfarin with quinidine can increase the amount of warfarin in your body. This means that you might have more side effects.

Depression medications

Taking certain depression drugs with quinidine can increase the amount of these medications in your body. This means that you might have more side effects. Examples of these drugs include:

  • doxepine
  • amitriptyline
  • imipramine
  • desipramine

Antipsychotic drugs

Taking certain antipsychotic drugs with quinidine can increase the amount of these medications in your body. This means you might have more side effects. Examples of these drugs include:

  • haloperidol
  • phenothiazines

Pain medications

Taking certain pain drugs with quinidine can decrease the amount of these drugs in your body. This means they may not work to treat your pain. Examples of these drugs include:

  • codeine
  • hydrocodone

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

This drug comes with several warnings.

Allergy warnings

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

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

Call 911 or go to the nearest emergency room if you develop these symptoms.

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death)

Food interaction warnings

  • 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.

Warnings for people with certain health conditions

For 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.

For people with myasthenia gravis: If you have this muscle condition, you shouldn’t use quinidine. Quinidine can worsen this condition.

For 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.

Warnings for other groups

For 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.

For women who are breastfeeding: Quinidine may pass through breast milk and cause serious effects in a child who is breastfed. Talk to your doctor if you breastfeed your child. You may need to decide whether to stop breastfeeding or stop taking this drug.

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 medication can be fatal.

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

How to take quinidine

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

Dosage to prevent and treat atrial fibrillation

Generic: Quinidine sulfate

  • Form: oral immediate-release tablet
  • Strengths: 200 mg and 300 mg

Generic: Quinidine sulfate

  • Form: oral extended-release tablet
  • Strength: 300 mg

Generic: Quinidine gluconate

  • Form: oral extended-release tablet
  • Strength: 324 mg

Adult dosage (ages 18 years and older)

  • Quinidine sulfate oral tablet
    • Treatment for irregular heart rate: There is no optimal dose for quinidine in treating irregular heart rates. You will likely start with a dose given 3 or 4 times a day. Your doctor will increase your dosage as needed to achieve a normal heart rate and rhythm.
    • Prevention of irregular heart rate and treatment of irregular heart rate in the ventricles: Typical dosage is 200 mg taken every 6 hours. Your doctor may increase your dosage. The levels of quinidine in your blood may be checked.
  • Quinidine sulfate oral extended-release tablet
    • Treatment for irregular heart rate: Typical dosage is 300–600 mg every 8–12 hours. Your doctor may increase your dosage after 4–5 doses.
    • Prevention of irregular heart rate and treatment of irregular heart rate in the ventricles: Typical dosage is 300 mg taken every 8–12 hours. Your doctor may increase your dosage.
  • Quinidine gluconate extended-release oral tablet
    • Treatment for irregular heart rate: There is no optimal dosage for quinidine in treating irregular heart rates. You will likely start with a dose given 3 times a day. Your doctor will increase your dosage as needed to achieve a normal heart rate and rhythm. While your dosage 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.

Dosage for malaria

Generic: Quinidine sulfate

  • Form: oral immediate-release tablet
  • Strengths: 200 mg and 300 mg

Adult dosage (ages 18 years and older)

When quinidine tablets are used to treat malaria, they‘re used after receiving initial treatment with the quinidine gluconate injection. Your doctor can tell you about dosage information.

Child dosage (ages 0–17 years)

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

Special dosage considerations

  • For people with liver problems: If you have liver problems, your doctor may lower your dosage of quinidine.

  • For people with heart problems: If you have heart failure, your doctor may lower your dosage of quinidine.

Dosage warnings

  • When you first start taking quinidine or increase your dosage, 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, your quinidine treatment 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 speak with your doctor or pharmacist about dosages that are right for you.

Take as directed

Quinidine is used for long-term treatment or prevention of heart rate problems. It’s a short-term drug treatment for malaria. It 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: You will increase your risk for dangerous side effects such as arrhythmia or liver damage.

What to do if you miss a 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: Your heart rate should return to normal, or it should take 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.

Important considerations for taking quinidine

Keep these considerations in mind if your doctor prescribes quinidine for you.

General

  • Quinidine can be taken with food to avoid an upset stomach.
  • 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 can not crush or chew quinidine sulfate extended-release or quinidine gluconate extended-release tablets.

Storage

  • Store quinidine at room temperature between 68°F and 77°F (20°C and 25°C).
  • Keep the drug away from light and high temperature.
  • Don’t store this medication in moist or damp areas, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

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 medication is working:

  • kidney function
  • liver function
  • heart function, including your blood pressure and heart rate

They may do tests to check for side effects that affect your blood cells, and electrocardiograms (tests that tell how well your heart is working).

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.

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.