Quinidine

What is Quinidine?

• Quinidine (Cardioquin; Cin-Quin; Duraquin; Quinact; Quinaglute; Quinalan; Quinatime; Quinidex; Quinora) is an antimalarial schizonticide and an antiarrhythmic agent with Class Ia activity.
• It is the d-isomer of quinine.
• It is the enantiomer of antimalarial agent quinine, originally derived from the bark of the cinchona tree.

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Quinidine structure

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Quinidine

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Quinidine-3d-balls

What are the uses of this medicine?

Quinidine (Cardioquin; Cin-Quin; Duraquin; Quinact; Quinaglute; Quinalan; Quinatime; Quinidex; Quinora) is used for the treatment of:

• Atrial fibrillation (safe and efficacious in combination with verapamil for the treatment of atrial fibrillation
• Atrial flutter
• Paroxysmal supraventricular tachycardia
• Atrioventricular nodal reentrant tachycardia
• Atrioventricular reentrant tachycardia
• Wolf Parkinson White syndrome
• Ventricular tachycardia
• Brugada syndrome
• Short QT interval syndrome

• Quinidine gluconate is acknowledged as an effective treatment of severe and complicated malaria both alone as a therapy or in combination with exchange transfusion.

How does this medicine work?

• Quinidine (kwin' i deen) and its stereoisomer quinine (kwye' nine) are natural cinchona alkaloids found in the powdered bark of the American cinchona tree.
• The bark powder was used for centuries in the prevention and therapy of malaria, but was also known to decrease heart palpitations.
• Quinidine was found to be the most potent of the antiarrhythmic substances extracted from the cinchona plant and was introduced into medical practice in the 1940s.
• Quinidine acts by depressing action potentials and is considered a myocardial depressant.

As Antiarrhythmic:

• Like other Class 1a antiarrhythmic agents, quinidine works by inhibiting the fast inward sodium current, depressing the phase 0 of the action potential hence dampening the excitability of cardiac muscles, which in turn prolongs the action potential and decreases automaticity.
• Quinidine's effect on fast inward sodium current is known as a 'use-dependent block' - this means at higher heart rates, the block increases, while at lower heart rates, the block decreases.
• Quinidine has also been shown to reduce potassium efflux during repolarization, inhibiting slow delayed rectifier potassium current, and show a "reverse use dependence" pattern (less current suppression at more frequent depolarizations) and calcium transport across cell membranes.

As Antimalarial:

• It works as an antimalarial agent by having activity against the erythrocytic stage of the Plasmodium species.
• It acts by building up in the parasite's food vacuole; it forms a complex with heme which prevents the crystallization in the parasite's food vacuole.
• Cytotoxic-free heme accumulates secondary to inhibited heme polymerase activity.

• Quinidine also has anticholinergic activity.

Who Should Not Use this medicine ?

This medicine cannot be used in patients with:

• Thrombocytopenia
• Thrombocytopenic purpura
• Hypersensitivity to quinine, mefloquine, quinidine, or to any component used in the drug preparation
• Heart block greater than a 1st degree
• Concurrent, amprenavir, cisapride, or ritonavir, fluoroquinolones drugs responsible for prolonging QT interval
• Congenital long QT interval
• AV block as the concurrent use of the drug can progress to complete block

What drug interactions can this medicine cause?

• Tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, and nutritional supplements you are taking.

Be sure to mention any of the following:

• acetazolamide
• amiodarone (Nexterone, Pacerone)
• antidepressants
• calcium channel blockers such as diltiazem (Cardizem, Cartia, Diltzac, others), felodipine, nicardipine (Cardene), nifedipine (Adalat, Procardia), nimodipine, or verapamil (Calan, Covera, Verelan, in Tarka)
• cimetidine (Tagamet HB)
• codeine products
• digoxin (Lanoxin)
• diuretics ('water pills')
• ketoconazole
• medications for mental illness such as haloperidol (Haldol), perphenazine, and thioridazine
• methazolamide
• mexiletine
• phenobarbital
• phenytoin (Dilantin, Phenytek)
• propranolol (Hemangeol, Inderal, Innopran)
• sodium bicarbonate (Arm and Hammer Baking Soda, in Zegerid OTC)
• warfarin (Coumadin, Jantoven)

Is this medicine FDA approved?

• It was formally approved for use in the United States in 1950 and was widely used to treat ventricular arrhythmias and to suppress the frequency of premature ventricular contractions.
• However, careful prospective studies demonstrated that suppression of ventricular arrhythmias can be associated with a decrease in survival and use of quinidine has fallen out of favor and now used largely for therapy of atrial flutter or fibrillation.
• Quinidine is also approved for intravenous use in treatment of life threatening Plasmodium falciparum malaria.

How should this medicine be used?

Recommended dosage: Atrial Fibrillation/Flutter to Sinus Rhythm Conversion:

• As initial therapy, administer two 200 mg (immediate-release) tablets every six hours.
• Administer two 324 mg Oral extended-release tablets (403 mg of quinidine base) every eight hours.

Reduction of Atrial Fibrillation/Flutter Relapse:

• As initial therapy, administer one tablet Oral immediate-release (166 mg of quinidine base) every six hours.
• As one regimen option, patients may have been administered one extended-release tablet (202 mg of quinidine base) every eight hours or twelve hours.

Ventricular arrhythmias suppression:

• The dosing regimens for ventricular arrhythmias suppression have not been adequately studied.
• However, these regimens have generally been similar to the regimen described above for the treatment of atrial fibrillation.

Administration:

• Quinidine comes as a tablet (quinidine sulfate) and an extended-release (long-acting) tablet (quinidine gluconate) to take by mouth.
• Quinidine sulfate tablets are usually is taken every 6 hours.
• Extended-release quinidine gluconate tablets are usually is taken every 8 to 12 hours.
• Take quinidine at around the same times every day.
• he extended-release tablet may be split in half.
• Swallow the whole or half tablets whole; do not chew or crush them.
• Quinidine helps control your condition but will not cure it.

What are the dosage forms and brand names of this medicine?

This medicine is available in fallowing doasage form:

• As a tablet (quinidine sulfate) and an extended-release (long-acting) tablet

This medicine is available in fallowing brand namesː

• Cardioquin; Cin-Quin; Duraquin; Quinact; Quinaglute; Quinalan; Quinatime; Quinidex; Quinora

What side effects can this medication cause?

The most common side effects of this medicine include:

• diarrhea
• fever
• rash
• arrhythmia
• abnormal electrocardiogram
• nausea/vomiting
• dizziness
• headache
• asthenia
• cerebral ischemia

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

Quinidine may cause serious side effects that can be life threatening, including:

• hepatotoxicity
• Autoimmune and inflammatory syndromes

What special precautions should I follow?

• In patients without implanted pacemakers who are at high risk of complete atrioventricular block (e.g., those with digitalis intoxication, second degree atrioventricular block, or severe intraventricular conduction defects), quinidine should be used only with caution.
• When quinidine is administered to patients with atrial flutter/fibrillation, the desired pharmacologic reversion to sinus rhythm may (rarely) be preceded by a slowing of the atrial rate with a consequent increase in the rate of beats conducted to the ventricles.
• In patients with the sick sinus syndrome, quinidine has been associated with marked sinus node depression and bradycardia.
• Grapefruit juice inhibits P450 3A4-mediated metabolism of quinidine to 3-hydroxyquinidine. Although the clinical significance of this interaction is unknown, grapefruit juice should be avoided.
• The rate and extent of quinidine absorption may be affected by changes in dietary salt intake; a decrease in dietary salt intake may lead to an increase in plasma quinidine concentrations.
• Administration of quinidine should be avoided in lactating women who continue to nurse.
• Quinidine has been associated with fever, mild jaundice and clinically apparent liver injury in up to 2% of treated patients.

What to do in case of emergency/overdose?

Symptoms of overdosage may include:

• ventricular arrhythmias
• hypotension
• vomiting
• diarrhea
• tinnitus
• high-frequency hearing loss
• vertigo
• blurred vision
• diplopia
• photophobia
• headache
• confusion
• delirium

Management of overdosage:

• In case of overdose, call the poison control helpline of your country. In the United States, call 1-800-222-1222.

• Overdose related information is also available online at poisonhelp.org/help.
• In the event that the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services. In the United States, call 911.
• In managing overdose, consider the possibilities of multiple-drug overdoses, drug-drug interactions, and unusual drug kinetics in your patient.
• Quinidine is not usefully removed from the circulation by dialysis.

Can this medicine be used in pregnancy?

• Pregnancy Category C.
• There are no adequate and well-controlled studies in pregnant women.
• Quinidine should be given to a pregnant woman only if clearly needed.

Can this medicine be used in children?

• Safety and effectiveness of antiarrhythmic use in pediatric patients have not been established.

What are the active and inactive ingredients in this medicine?

Active ingredient:

• Quinidine Gluconate

Inactive ingredients:

• Carnauba wax
• Ethylcellulose
• Magnesium stearate
• Povidone

Who manufactures and distributes this medicine?

• Watson Laboratories, Inc.
• Corona, CA USA

What should I know about storage and disposal of this medication?

• Dispense in a well-closed, light-resistant container with child-resistant closure.
• Store at 20°-25°C (68°-77°F).

List of antiarrhythmic agents:

• Amiodarone
• Disopyramide
• Dofetilide
• Dronedarone
• Flecainide
• Ivabradine
• Mexiletine
• Procainamide
• Propafenone
• Quinidine

• Dailymed label info on Quinidine
• FDA Quinidine

Quinidine Resources
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