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 be begun 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.