July 28, 2016
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Discontinued Warning IconPlease Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

Quinidex Side Effects Center

Medical Editor: John P. Cunha, DO, FACOEP

Last reviewed on RxList 2/7/2016

Quinidex (quinidine sulfate) is an antiarrhythmic drug used to treat or prevent many types of irregular heartbeats (heart arrhythmias such as atrial fibrillation). Quinidex is available in generic form. Common side effects of Quinidex include diarrhea, nausea, vomiting, loss of appetite, stomach pain or cramps, a burning feeling in throat or chest (e.g., heartburn), depression, muscle or joint pain, headache, dizziness, skin rash, skin dryness/peeling/flaking, or flushing (warmth, redness, or tingly feeling).

Dosage for quinidine sulfate is based on medical condition and response to treatment. For adults, the dosage ranges from 400 to 4000 mg/day. Quinidine sulfate should not be used with the following medications because very serious (possibly fatal) interactions may occur: HIV protease inhibitors, azole antifungals, propafenone, cisapride, arbutamine, or mefloquine. Other medications that may interact with quinidine sulfate include amiodarone, dofetilide, pimozide, procainamide, sotalol, antibiotics, ziprasidone, mesoridazine, thioridazine, antacids, barbiturates, carbamazepine, rifamycins, phenytoin, carbonic anhydrase inhibitors, aripiprazole, atomoxetine, codeine, hydrocodone, loperamide, medication for high blood pressure, quinupristin/dalfopristin, etravirine, oramprenavir/fosamprenavir. During pregnancy, quinidine sulfate should be used only when prescribed. This medication passes into breast milk. Consult your doctor before breastfeeding.

Our Quinidine Sulfate (brand name: Quinidex) Side Effects Drug Center provides a comprehensive view of available drug information on the potential side effects when taking this medication.

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 is Patient Information in Detail?

Easy-to-read and understand detailed drug information and pill images for the patient or caregiver from Cerner Multum.

Quinidex in Detail - Patient Information: Side Effects

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

Call your doctor at once if you have a serious side effect such as:

  • vomiting and diarrhea;
  • ringing in the ears, hearing loss, severe dizziness;
  • feeling like you might pass out;
  • changes in vision, pain behind your eyes, increased sensitivity of your eyes to light;
  • white patches on your eyes;
  • cloudiness in the pupils or iris of your eyes;
  • a new or a worsening irregular heartbeat pattern;
  • pale or yellowed skin, dark colored urine, fever, confusion or weakness;
  • nausea, stomach pain, low fever, loss of appetite, clay-colored stools;
  • seizure (convulsions);
  • easy bruising, unusual bleeding (nose, mouth, vagina, or rectum), purple or red pinpoint spots under your skin; or
  • bronchospasm (wheezing, chest tightness, trouble breathing).

Less serious side effects may include:

  • mild nausea, vomiting, or diarrhea;
  • heartburn;
  • depressed mood;
  • muscle or joint pain;
  • headache, dizziness;
  • mild skin rash;
  • skin dryness, peeling, or flaking; or
  • flushing (warmth, redness, or tingly feeling).

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.

Read the entire detailed patient monograph for Quinidex (Quinidine)

What is Patient Information Overview?

A concise overview of the drug for the patient or caregiver from First DataBank.

Quinidex Overview - Patient Information: Side Effects

SIDE EFFECTS: Diarrhea, nausea, vomiting, loss of appetite, stomach pain/cramps, or a burning feeling in throat or chest (e.g., heartburn) may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Seek immediate medical attention if any of these unlikely but serious side effects occur: severe dizziness, fainting, sudden change in heartbeat (faster/slower/more irregular).

Tell your doctor immediately if any of these unlikely but serious side effects occur: vision changes, eye pain, muscle pain, unusual sweating or shakiness (signs of low blood sugar).

Tell your doctor immediately if any of these rare but very serious side effects occur: unexplained fever/signs of infection (e.g., persistent sore throat), easy bruising/bleeding, extreme tiredness, dark urine, persistent nausea/vomiting, yellowing eyes/skin, lupus-like symptoms (joint/muscle pain, chest pain, change in the amount of urine).

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

One type of reaction (cinchonism) can occur after even a single dose of this drug. Contact your doctor of pharmacist promptly if you notice symptoms such as ringing in the ears, sudden hearing problems, headache, blurred vision, confusion. Your dosage may need to be adjusted.

Certain long-acting brands of quinidine may appear as a whole tablet in the stool. This is the empty shell left after the medicine has been absorbed by the body. It is harmless.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Read the entire patient information overview for Quinidex (Quinidine)

What is Prescribing information?

The FDA package insert formatted in easy-to-find categories for health professionals and clinicians.

Quinidex FDA Prescribing Information: Side Effects
(Adverse Reactions)


Quinidine preparations have been used for many years, but there are only sparse data from which to estimate the incidence of various adverse reactions. The adverse reactions most frequently reported have consistently been gastrointestinal, including diarrhea, nausea, vomiting, and heartburn/esophagitis. In one study of 245 adult outpatients who received quinidine to suppress premature ventricular contractions, the incidences of reported adverse experiences were as shown in the table below. The most serious quinidine-associated adverse reactions are described above under WARNINGS.

Adverse Experiences in a 245-Patient PVC Trial
Incidence (%)
85 (35)
"upper Gastrointestinal distress"
55 (22)
37 (15)
18 (7)
17 (7)
16 (7)
angina-like pain
14 (6)
13 (5)
11 (5)
visual problems
 8 (3)
change in sleep habits
 7 (3)
 6 (2)
 5 (2)
 3 (1)

Vomiting and diarrhea can occur as isolated reactions to therapeutic levels of quinidine, but they also may be the first signs of cinchonism , a syndrome that also may include tinnitus, reversible high-frequency hearing loss, deafness, vertigo, blurred vision, diplopia, photophobia, headache, confusion, and delirium. Cinchonism is most often a sign of chronic quinidine toxicity, but it may appear in sensitive patients after a single moderate dose.

A few cases of hepatotoxicity , including granulomatous hepatitis, have been reported in patients receiving quinidine. All of these have appeared during the first few weeks of therapy, and most (not all) have remitted once quinidine was withdrawn.

Autoimmune and inflammatory syndromes associated with quinidine therapy have included pneumonitis, fever, urticaria, flushing, exfoliative rash, bronchospasm, psoriasiform rash, pruritus and lymphadenopathy, hemolytic anemia, vasculitis, thrombocytopenic purpura, uveitis, angioedema, agranulocytosis, the sicca syndrome, arthralgia, myalgia, elevation in serum levels of skeletal-muscle enzymes, and a disorder resembling systemic lupus erythematosus.

Convulsions, apprehension, and ataxia have been reported, but it is not clear that these were not simply the results of hypotension and consequent cerebral hypoperfusion. There are many reports of syncope. Acute psychotic reactions have been reported to follow the first dose of quinidine, but these reactions appear to be extremely rare.

Other adverse reactions occasionally reported include depression, mydriasis, disturbed color perception, night blindness, scotomata, optic neuritis, visual field loss, photosensitivity, and abnormalities of pigmentation.


Read the entire FDA prescribing information for Quinidex (Quinidine)

Quinidex - User Reviews

Quinidex User Reviews

Now you can gain knowledge and insight about a drug treatment with Patient Discussions.

Here is a collection of user reviews for the medication Quinidex sorted by most helpful. Patient Discussions FAQs

Report Problems to the Food and Drug Administration


You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

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