Quinidine (Quinidine Sulfate) - Indications and Dosage

INDICATIONS AND USAGE

Conversion of Atrial Fibrillation/Flutter

In patients with symptomatic atrial fibrillation/flutter whose symptoms are not adequately controlled by measures that reduce the rate of ventricular response, quinidine sulfate is indicated as a means of restoring normal sinus rhythm. If this use of quinidine sulfate does not restore sinus rhythm within a reasonable time (see DOSAGE AND ADMINISTRATION), then quinidine sulfate should be discontinued.

Reduction of Frequency of Relapse into Atrial Fibrillation/Flutter

Chronic therapy with quinidine sulfate is indicated for some patients at high risk of symptomatic atrial fibrillation/flutter; generally patients who have had previous episodes of atrial fibrillation/flutter that were so frequent and poorly tolerated as to outweigh, in the judgment of the physician and the patient, the risks of prophylactic therapy with quinidine sulfate. The increased risk of death should specifically be considered. Quinidine sulfate should be used only after alternative measures (e.g., use of other drugs to control the ventricular rate) have been found to be inadequate.

In patients with histories of frequent symptomatic episodes of atrial fibrillation/flutter, the goal of therapy should be an increase in the average time between episodes. In most patients, the tachyarrhythmia will recur during therapy, and a single recurrence should not be interpreted as therapeutic failure.

Suppression of Ventricular Arrhythmias

Quinidine sulfate is also indicated for the suppression of recurrent documented ventricular arrhythmias, such as sustained ventricular tachycardia, that in the judgment of the physician are life-threatening. Because of the proarrhythmic effects of quinidine, its use with ventricular arrhythmias of lesser severity is generally not recommended, and treatment of patients with asymptomatic ventricular premature contractions should be avoided. Where possible, therapy should be guided by the results of programmed electrical stimulation and/or Holter monitoring with exercise.

Antiarrhythmic drugs (including quinidine sulfate) have not been shown to enhance survival in patients with ventricular arrhythmias.

DOSAGE AND ADMINISTRATION

Conversion of Atrial Fibrillation/Flutter to Sinus Rhythm

Especially in patients with known structural heart disease or other risk factors for toxicity, initiation or dose-adjustment of treatment with quinidine sulfate should generally be performed in a setting where facilities and personnel for monitoring and resuscitation are continuously available. Patients with symptomatic atrial fibrillation/flutter should be treated with quinidine sulfate only after ventricular rate control (e.g., with digitalis or β-blockers) has failed to provide satisfactory control of symptoms. Adequate trials have not identified an optimal regimen of quinidine sulfate for conversion of atrial fibrillation/flutter to sinus rhythm. Therapy with quinidine sulfate should begin with one tablet (300 mg; 249 mg of quinidine base) every 8 to 12 hours. If this regimen is well tolerated, if the serum quinidine level is still well within the laboratory’s therapeutic range, and if this regimen has not resulted in conversion, then the dose may be cautiously raised. If, at any point during administration, the QRS complex widens to 130% of its pre-treatment duration; the QTc interval widens to 130% of its pre-treatment duration and is then longer than 500 ms; P waves disappear; or the patient develops significant tachycardia, symptomatic bradycardia, or hypotension, then quinidine sulfate is discontinued, and other means of conversion (e.g., direct-current cardioversion) are considered.

Reduction of Frequency of Relapse into Atrial Fibrillation/Flutter

In a patient with a history of frequent symptomatic episodes of atrial fibrillation/flutter, the goal of therapy with quinidine sulfate should be an increase in the average time between episodes. In most patients, the tachyarrhythmia will recur during therapy with quinidine sulfate, and a single recurrence should not be interpreted as therapeutic failure.

Especially in patients with known structural heart disease or other risk factors for toxicity, initiation or dose-adjustment of treatment with quinidine sulfate should generally be performed in a setting where facilities and personnel for monitoring and resuscitation are continuously available. Monitoring should be continued for two or three days after initiation of the regimen on which the patient will be discharged.

Therapy with quinidine sulfate should begin with one tablet (300 mg; 249 mg of quinidine base) every eight to twelve hours. If this regimen is well tolerated, if the serum quinidine level is still well within the laboratory’s therapeutic range, and if the average time between arrhythmic episodes has not been satisfactorily increased, then the dose may be cautiously raised. The total daily dosage should be reduced if the QRS complex widens to 130% of its pre-treatment duration; the QTc interval widens to 130% of its pre-treatment duration and is then longer than 500 ms; P waves disappear; or the patient develops significant tachycardia, symptomatic bradycardia, or hypotension.

Suppression of Ventricular Arrhythmias

Dosing regimens for the use of quinidine sulfate in suppressing life-threatening ventricular arrhythmias have not been adequately studied. Described regimens have generally been similar to the regimen described just above for the prophylaxis of symptomatic atrial fibrillation/flutter. Where possible, therapy should be guided by the results of programmed electrical stimulation and/or Holter monitoring with exercise.

HOW SUPPLIED

Quinidine Sulfate Extended-release Tablets, USP are 300 mg, white film-coated, round, unscored tablets debossed “93”“175” on one side and plain on the other side.

The tablets are available in bottles of 100 and 250.

Store at controlled room temperature, between 20° and 25°C (68° and 77°F) (see USP).

Dispense in a tight, light-resistant container as defined in the USP, with a child-resistant closure (as required).

Manufactured By:

TEVA PHARMACEUTICALS USA

Sellersville, PA 18960

Rev. C 6/2003