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Overview: Quinidine is taken for certain types of abnormal heart rhythms or to treat malaria. It helps your heart beat normally and kills the parasite that causes malaria. Common side effects include nausea, vomiting, and diarrhea. Notify your health care provider right away if you develop shortness of breath or bruise more easily than usual.

Uses

What is quinidine used for?

Quinidine is commonly used for the following conditions.

Quinidine may also be used for other conditions as determined by your healthcare provider.

How does quinidine work (mechanism of action)?

For abnormal heart rhythms, quinidine works by blocking certain electrical signals in the heart that cause it to beat too fast or irregularly. This helps the heart beat normally again.

For malaria, quinidine helps to kill the parasite that causes it.

How is quinidine supplied (dosage forms)?

Dosage forms and strengths

  • 324 mg extended-release oral tablets
  • 200 mg, 300 mg oral tablets

How should I store quinidine?

Quinidine should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Side Effects

What are the most common side effects of quinidine?

The most common side effects of quinidine are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

  • Diarrhea
  • Nausea
  • Vomiting
  • Heartburn

There may be other side effects of quinidine that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of quinidine?

While less common, the most serious side effects of quinidine are described below, along with what to do if they happen.

Heart Rhythm Changes. Quinidine may cause serious heart rhythm problems that can lead to an irregular heartbeat and fainting. In rare cases, this may cause the heart to suddenly stop beating (cardiac arrest). Some people have a higher risk of this, including people with existing heart disease or who take other medicines that affect the heart. Get emergency help if you have any of the following signs of heart rhythm changes.

  • Chest pain
  • Shortness of breath
  • Feeling dizzy, lightheaded, or fainting
  • Changes in your heart rate or rhythm, such as a fast, slow, pounding or skipping heartbeat

Blood Disorders. Quinidine can cause blood disorders, such as agranulocytosis, hemolytic anemia, and low platelet levels (thrombocytopenia). Tell your healthcare provider and get help right away if you have any of the following symptoms of blood disorders.

  • Fever
  • Shortness of breath
  • Pale or yellowish skin
  • Easy bruising or bleeding
  • Frequent infection
  • Unusual weakness or tiredness
  • Dizziness, lightheadedness, or feeling like you are about to pass out
  • Headache
  • Fast or abnormal heartbeat

Severe Allergic Reactions. Quinidine may cause allergic reactions, which can be serious. Stop taking quinidine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Liver Damage. Liver damage, also called hepatotoxicity, can happen when taking quinidine. Call your healthcare provider right away if you have any of the following symptoms of liver damage.

  • Nausea or vomiting
  • Stomach or belly pain
  • Fever
  • Weakness or unusual tiredness
  • Itching
  • Loss of appetite
  • Light-colored poop
  • Dark-colored urine (pee)
  • Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

Immune System Reactions. Quinidine can cause inflammation of your liver, lungs, eyes, blood vessels, or lymph vessels and cause symptoms that look like a condition called lupus. Call your healthcare provider right away if you develop any of the following symptoms.

  • Rash
  • Joint pain
  • Fever
  • Weakness or unusual tiredness
  • Cough
  • Blurred or double vision, eye pain or redness, sensitivity to light, or vision loss

Warnings & Precautions

Who should not use quinidine?

Allergies to Ingredients. People who are allergic to any of the following should not take quinidine.

  • Quinidine
  • Quinaglute
  • Quinidex
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific quinidine products they stock.

Heart Block. You should not take quinidine if you have certain types of heart block, also called atrioventricular (AV) block, unless you have a pacemaker.

Myasthenia Gravis. If you have myasthenia gravis you should not take quinidine.

Blood Disorders. You should not take quinidine if you have certain blood disorders, such as immune thrombocytopenia or a history of thrombocytopenic purpura from quinidine or quinine. 

What should I know about quinidine before using it?

Do not take quinidine unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not chew or crush the extended-release tablets.

Do not share quinidine with other people, even if they have the same condition as you. It may harm them.

Keep quinidine out of the reach of children.

If you have malaria, It is important to complete your prescribed course of quinidine, even if your symptoms get better or go away. This will reduce the risk that future infections are resistant to quinidine or other similar medicines.

What should I tell my healthcare provider before using quinidine?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if quinidine is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

Other Medicines and Supplements. Quinidine may interact with other medicines and supplements. Before using quinidine, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section below for more details.

Pregnancy. It is not known if or how quinidine could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. Quinidine passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take quinidine while breastfeeding.

Interactions

Does quinidine interact with foods or drinks?

Do not drink grapefruit juice while taking quinidine. Grapefruit juice can increase your blood levels of quinidine, which may lead to serious side effects.

Changes in the amount of salt you have can affect blood levels of quinidine. It is best to consume about the same amount of salt every day to keep the amount of quinidine in your blood consistent.

It is unknown if drinking alcohol will affect quinidine. 

Does quinidine interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using quinidine.

  • A carbonic anhydrase inhibitor, such as zonisamide (Zonegran and others), acetazolamide (Diamox), or methazolamide
  • A calcium channel blocker, such as diltiazem (Cardizem CD and others) or verapamil (Verelan, Verelan PM), which is a medicine used for high blood pressure or other conditions
  • Phenytoin (Dilantin, Phenytek, and others), which is a medicine to control seizures
  • Propranolol (Inderal LA, Innopran XL), which is a medicine that may be used for certain heart conditions or to reduce blood pressure
  • Any medicine used to control your heart rate or rhythm (antiarrhythmic)
  • Phenobarbital, which is a medicine that may be used to treat seizures
  • Cimetidine (Tagamet HB), which is a medicine used for heartburn
  • Rifampin, which is a medicine commonly used to treat an infection called tuberculosis 
  • Ketoconazole, which is a medicine used for fungal infections
  • Warfarin, which is a blood thinner 
  • Digoxin (Lanoxin), which is a medicine used to treat irregular heartbeat and some types of heart failure
  • Haloperidol, which is a medicine for certain mental health conditions 
  • Nifedipine (Adalat, Procardia XL), felodipine, or nicardipine (Cardene), which is a medicine used for high blood pressure or chest pain 
  • A diuretic, also called a water pill, which is a medicine used to reduce edema (fluid retention) and blood pressure 
  • Sodium bicarbonate, which is a medicine used for heartburn and stomach ulcers and is in some over-the-counter (OTC) and prescription medicines, such as Zegerid, Zegerid OTC, and Alka-Seltzer
  • Medicines that can cause QT prolongation, which is a potentially dangerous heart rhythm problem

Some other medicines may alter the blood levels of quinidine and vice versa. Tell your healthcare provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with quinidine. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much quinidine?

If you or someone else has used too much quinidine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of quinidine?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.