Quinidex Extentabs

Generic name: Quinidine sulfate.

Other brand names: Cin-Quin, Novaquinidin, Quinora.

Quinidex is an anti-arrhythmic. It alters nerve impulses within the heart to regulate heartbeat.

Quick Facts About Quinidex


Used to correct irregular heart rhythms and to slow an abnormally fast heartbeat.

Quinidex Dosage

Adhere to regular dosage schedule, taking only the prescribed amount, not increasing or decreasing dose. Swallow tablets whole, not crushed or chewed. May take with water, milk, or other liquid.

  • Usual adult dose: 1 or 2 tablets every 8 to 12 hours.
  • Usual child dose: not generally prescribed for children.
  • Missed dose: take as soon as possible, if within 2 hours of next dose. Otherwise, do not take missed dose; go back to regular schedule. Do not double doses.

Quinidex Side Effects

Overdose symptoms:

abnormal heart rhythms, changes in heart function, coma, decreased breathing, decreased production of urine, fluid in the lungs, low blood pressure, seizures. If you suspect an overdose, immediately seek medical attention.

More common side effects: abdominal pain, diarrhea, hepatitis, inflammation of esophagus (gullet), loss of appetite, nausea, vomiting.

Less common or rare Quinidex side effects: allergic reaction (swelling of face, lips, tongue, throat, arms and legs, sore throat, fever and chills, difficulty swallowing, chest pain); anemia; apprehension; asthma attack; blind spots; blood clots; blurred vision; changes in skin pigmentation; confusion; delirium; depression; dilated pupils; disturbed color perception; double vision; eczema; excitement; feinting; fever; fluid retention; flushing; headache; hearing changes; hepatitis; hives; inability to breathe; intense itching; intolerance to light; irregular heartbeats; joint pain; lack of coordination; low blood pressure; lupus erythematosus; mental decline; muscle pain; night blindness; psoriasis; rash; reddish or purplish spots below the skin; skin eruptions and scaling; skin sensitivity to light; vertigo; vision changes. Another possible side effect is cinchonism—a condition with symptoms such as ringing in ears, loss of hearing, dizziness, light-headedness, headache, nausea, disturbed vision.


Digoxin (Lanoxin) concentrations may increase or caf double when taken with Quinidex.

Inform your doctor before combining Quinidex with:

amiodarone (Cordarone); antacids with magnesium such as Maalox and Mylanta; antidepressants such as Elavil and Tofranil; antispasmodics such as Bentyl; aspirin blood thinners such as Coumadin; cimetidine (Tagamet); diuretics such as Diamox and Daranide; decamethonium; disopyramide (Norpace); ketoconazole (Nizoral); major tranquilizers such as Stelazine and Thorazine; nifedipine (Procardia); phenobarbital: phenytoin (Dilantin); physostigmine (Antilirium); ranitidine (Zantac); reserpine (Diupres); rifampin (Rifadin); sodium bicarbonate; sucralfate (Carafote); thiazide diuretics such as Dyazide and HydroDIURIL; verapamil (Calan).

No known food/other substance interactions. 

Special Cautions

If pregnant or planning to become pregnant, inform your doctor immediately. Appears in breast milk, could affect a nursing infant.

No special precautions apply to seniors.

Not generally prescribed for children.

  • Do not confuse with quinine, which is prescribed for nighttime leg cramps and malaria.
  • Should not take if you have certain heartbeat irregularities such as heart block; or if you have myasthenia gravis (abnormal muscle weakness); or if sensitive to or allergic to Quinidine or cinchona derivatives. In rare cases there have been severe allergic reactions.
  • Use with caution if you have: poorly controlled heart disease or circulatory problems, partial hearth block, kidney or liver disease.
  • Immediately contact your doctor if you faint.
  • If you develop an unexplained fever, contact your doctor; may be a sign of liver damage.


HealthSurvey.org provides accurate and independent information prescription pills, over-the-counter medicines and natural products. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment. If you have questions about  dosage, or Quinidex side effects, please contact your healthcare provider