Quinidine sulfate is primarily used in the treatment of certain heart rhythm disorders, such as atrial fibrillation and ventricular tachycardia. It works by stabilizing the heart's electrical activity, helping to restore and maintain a normal rhythm. Additionally, it is sometimes employed to prevent recurrent episodes of malaria, particularly in regions where the parasite has developed resistance to other antimalarial drugs. The compound is also utilized in diagnostic tests to evaluate the presence of specific cardiac conditions. Due to its potent effects, it is administered under strict medical supervision to monitor for potential side effects, such as arrhythmias or gastrointestinal disturbances.