Quinidine is primarily used as an antiarrhythmic medication to treat irregular heart rhythms, 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 in the treatment of malaria, particularly for cases resistant to other medications, due to its ability to interfere with the parasite's lifecycle. Quinidine is also used in diagnostic settings to evaluate certain heart conditions, such as Brugada syndrome. However, its use requires careful monitoring due to potential side effects, including cardiac complications and drug interactions.