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Drugs reference index «Quinidine»


Brand names: Quinidine, Quinidine sulfate

Why is Quinidine prescribed?

Quinidine is used to correct certain types of irregular heart rhythms and to slow an abnormally fast heartbeat.

Most important fact about Quinidine

It is important to take only the prescribed amount of Quinidine—no more and no less. Try to keep your doses at regularly spaced intervals, and be sure not to miss any.

How should you take Quinidine?

Take quinidine exactly as prescribed.

  • If you miss a dose...Take it as soon as you remember, if it is within 2 hours of your scheduled time. If you do not remember until later, skip the dose you missed and go back to your regular schedule. Do not take 2 doses at once.
  • Storage instructions...Store at room temperature in a tightly closed container, away from light.

What side effects may occur?

Side effects cannot be anticipated. If any develop or change in intensity, inform your doctor as soon as possible. Only your doctor can determine if it is safe for you to continue taking quinidine.

  • Side effects include:Abdominal pain, diarrhea, hepatitis, inflammation of the esophagus (gullet), loss of appetite, nausea, vomiting

Another possible side effect is a sensitivity reaction called cinchonism. Symptoms include blurred or double vision, confusion, delirium, diarrhea, headache, intolerance to light, hearing loss, ringing in the ears, vertigo, and vomiting.

Why should Quinidine not be prescribed?

Do not take Quinidine if you have ever had an allergic reaction to quinidine. Also avoid Quinidine if quinine or quinidine causes you to bruise easily.

Quinidine is prescribed only for certain specific types of heart irregularity, and should be avoided when other irregularities are present. It could also prove harmful if you have myasthenia gravis (abnormal muscle weakness) or a similar condition.

Special warnings about Quinidine

Quinidine is reserved for certain kinds of dangerously rapid heart irregularities. It works well for some people, providing them with significant symptomatic relief. However, you should know that—on average for all cases—it has not been shown to improve chances of long-term survival, and could actually lower the odds.

Remember, too, that under certain conditions (slow heart rate, low potassium or magnesium levels) quinidine can cause certain types of heart irregularity. It can also cause the condition known as heart block, and should be used with caution if you have partial heart block.

Also use quinidine cautiously if you have kidney or liver disease. Your doctor will check your blood count and liver and kidney function periodically during long-term therapy.

There have been rare cases of severe allergic reaction to quinidine, especially during the first few weeks of therapy. Discuss any allergic reactions you have experienced with your doctor.

Do not confuse quinidine with quinine, which, although related, is used to treat malaria.

Possible food and drug interactions when taking Quinidine

Concentrations of digoxin in your blood may increase or even double when Quinidine is taken with quinidine. Your doctor may need to reduce the amount of digoxin you take.

A decrease in your salt intake can lead to a higher blood level of quinidine. Try to keep the salt in your diet constant. Grapefruit juice may also have an impact on quinidine levels. It's best to avoid it.

If quinidine are taken with certain other drugs, the effects of either could be increased, decreased, or altered. It is especially important to check with your doctor before combining quinidine with the following:

AmiodaroneAntacids containing magnesiumAntispasmodic drugsAspirinBeta-blocking blood pressure medicationsBlood thinners such as warfarinCertain antidepressantsCertain diuretic drugsCimetidineCodeineDecamethoniumDigitoxinDiltiazemDisopyramideFelodipineHaloperidolHydrocodoneKetoconazoleMajor tranquilizersMexiletineNicardipineNifedipineNimodipinePhenobarbitalPhenytoinPhysostigmineProcainamideReserpineRifampinSodium bicarbonateSucralfateThiazide diureticsVerapamil

Special information if you are pregnant or breastfeeding

The effects of quinidine during pregnancy have not been adequately studied. If you are pregnant or plan to become pregnant, inform your doctor immediately. quinidine appears in breast milk and can affect a nursing infant. If Quinidine is essential to your health, your doctor may advise you to discontinue breastfeeding until your treatment is finished.

Recommended dosage for Quinidine


The usual dosage is 300 milligrams quinidine every 8 to 12 hours.


Any medication taken in excess can have serious consequences. If you suspect an overdose, seek medical treatment immediately.

  • The symptoms of quinidine overdose may include:Abnormal heart rhythms, blurred or double vision, confusion, delirium, diarrhea, headache, intolerance to light, loss of hearing, low blood pressure, ringing in the ears, vertigo, vomiting
  • Quinidine Prescribing Information (FDA)
  • Quinidine Professional Patient Advice (Wolters Kluwer)
  • quinidine Concise Consumer Information (Cerner Multum)
  • quinidine Oral, Injection, Intramuscular Advanced Consumer (Micromedex) - Includes Dosage Information

See Also...

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