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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 gluconate is indicated as a means of restoring normal sinus rhythm. If this use of quinidine gluconate does not restore sinus rhythm within a reasonable time (see DOSAGE AND ADMINISTRATION), then quinidine gluconate should be discontinued.
Reduction of Frequency of Relapse into Atrial Fibrillation/Flutter
Chronic therapy with quinidine gluconate 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 gluconate. The increased risk of death should specifically be considered. Quinidine gluconate 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 gluconate 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 gluconate) have not been shown to enhance survival in patients with ventricular arrhythmias.
DOSAGE AND ADMINISTRATION
The dose of quinidine delivered by quinidine gluconate extended-release tablets may be titrated by breaking a tablet in half. If tablets are crushed or chewed, their extended-release properties will be lost.
The dosage of quinidine varies considerably depending upon the general condition and the cardiovascular state of the patient.
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 gluconate 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 gluconate 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 gluconate for conversion of atrial fibrillation/flutter to sinus rhythm. In one reported regimen, the patient first receives two tablets (648 mg; 403 mg of quinidine base) of quinidine gluconate every eight hours. If this regimen has not resulted in conversion after 3 or 4 doses, then the dose is cautiously increased. 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 gluconate is discontinued, and other means of conversion (e.g., direct-current cardioversion) are considered.
In another regimen sometimes used, the patient receives one tablet (324 mg; 202 mg of quinidine base) every eight hours for two days; then two tablets every twelve hours for two days; and finally two tablets every eight hours for up to four days. The four-day stretch may come at one of the lower doses if, in the judgment of the physician, the lower dose is the highest one that will be tolerated. The criteria for discontinuation of treatment with quinidine gluconate are the same as in the other regimen.
Reduction in the 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 gluconate should be an increase in the average time between episodes. In most patients, the tachyarrhythmia will recur during therapy with quinidine gluconate, 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 gluconate 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 gluconate should begin with one tablet (324 mg; 202 mg of quinidine base) every eight or 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 Life-Threatening Ventricular Arrhythmias
Dosing regimens for the use of quinidine gluconate 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.
Quinidine Gluconate Extended-release Tablets USP 324 mg are 13/32", unscored, round, off-white tablets imprinted DAN and 5538 supplied in bottles of 100, 250, and 500.
Dispense in a well-closed, light-resistant container with child-resistant closure.
Store at 20°-25°C (68°-77°F). [See USP controlled room temperature.]
Watson Laboratories, Inc. Corona, CA 92880, USA. FDA Rev date: 1/8/2001
Last reviewed on RxList: 10/7/2008
This monograph has been modified to include the generic and brand name in many instances.
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