Procainamide is a class I antiarrhythmic drug used in the treatment of atrial fibrillation.

This is the drug of choice in the setting of Wolff-Parkinson-White syndrome with atrial fibrillation.

Procainamide can cause drug induced systemic lupus erythematosus (SLE). Anti-histone antibodies are present in about 95% of these cases. Other medications known to cause drug induced SLE include hydralazine (used to treat hypertension) and isoniazid (used to treat tuberculosis).