Generic name: quinidine (oral/injection) (KWIH nih deen)
Brand name: Quin-G, Cardioquin, Quinora, Quinidex Extentabs, Quinaglute Dura-Tabs, Quin-Release
Dosage forms: oral tablet (200 mg; 300 mg); oral tablet, extended release (324 mg)
Drug class: Group I antiarrhythmics

Quinidine is used to help keep the heart beating normally in people with certain heart rhythm disorders, usually after other treatments have failed. Quinidine has not been proven to lower the risks of stroke or death.

Quinidine is also used to treat a life-threatening form of malaria.

Quinidine may also be used for purposes not listed in this medication guide.


quinidine may increase your risk of death, especially if you have heart problems affecting the tissues or valves of your heart (including heart problems you may have been born with). Ask your doctor about the risks and benefits of using quinidine.

Before taking this medicine

Although quinidine can reduce episodes of irregular heart rhythm, this medicine may increase your risk of death. Your risk may be higher if you have heart problems affecting the tissues or valves of your heart (including heart problems you may have been born with). Ask your doctor about the risks and benefits of using quinidine.

You should not use quinidine if you are allergic to it, or if you have:

  • a serious heart condition called "AV block" (unless you have a pacemaker);
  • myasthenia gravis; or
  • a history of bruising or bleeding after using quinidine or quinine.

Tell your doctor if you have ever had:

  • a heart condition called "sick sinus syndrome";
  • slow heartbeats;
  • congestive heart failure;
  • a heart valve disorder, a hole in your heart, an enlarged heart, or mitral valve prolapse;
  • long QT syndrome (in you or a family member);
  • Marfan syndrome;
  • heart rhythm problems with past use of quinidine;
  • liver or kidney disease; or
  • an electrolyte imbalance (such as low levels of potassium or magnesium in your blood).

It is not known whether this medicine will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

You should not breastfeed while using quinidine.

How is quinidine given?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed. Your blood pressure and heart rate should be monitored in a hospital or clinic setting when you start using quinidine, and whenever your dose is changed.

Do not change your medication dose or schedule without your doctor's advice.

Quinidine oral is taken by mouth. Quinidine injection is given as an infusion into a vein. A healthcare provider will give you this injection if you are unable to take the medicine by mouth.

Do not crush or chew an extended-release tablet. Swallow it whole. You may break the tablet in half if your doctor instructs you to.

When quinidine is given to treat malaria, you may also be given antibiotic medication. Keep using the antibiotic for as long as your doctor has prescribed.

Store at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

Because you will receive quinidine injection in a clinical setting, you are not likely to miss a dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of quinidine can be fatal.

Overdose can cause vomiting, diarrhea, ringing in your ears, hearing loss, severe dizziness, double vision, confusion, irregular heartbeats, or feeling like you might pass out.

What should I avoid while using quinidine?

Grapefruit may interact with oral quinidine and lead to unwanted side effects. Avoid the use of grapefruit products.

Quinidine side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness (like you might pass out);
  • vomiting and diarrhea;
  • confusion, ringing in your ears, hearing loss;
  • severe eye redness, vision problems, increased sensitivity to light;
  • wheezing, chest tightness, trouble breathing;
  • easy bruising, unusual bleeding;
  • pale or yellowed skin, stomach pain (upper right side), dark urine;
  • fever, chills, sore throat, mouth sores, swollen glands;
  • skin itching, flaking, blistering, peeling, or rash on your cheeks or arms that worsens in sunlight;
  • muscle or joint pain; or
  • dry mouth, trouble swallowing.

Common side effects may include:

  • chest pain, pounding heartbeats;
  • dizziness;
  • heartburn, nausea, vomiting, diarrhea;
  • flushing (sudden warmth, redness, or tingly feeling);
  • feeling weak or tired; or
  • pain or tenderness where the medicine was injected (may last for several weeks).

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect quinidine?

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Many drugs can affect quinidine. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.