We have prescribed procainamide to thousands of patients, as has any large medical center. Usually, we like to limit its use to a few weeks if possible. Side effects can become manifest in days, weeks, or months. The positive ANA is common, and not of concern in and of itself. It should not be checked routinely, as it will likely be abnormal. The hematological side effects are rare, the lupus type side effects, such as arthritis, are more common. Gastrointestinal side effects, such as diarrhea, can also occur. There are some patients in whom we use it long term. Unfortunately, all the anti-arrhythmic drugs have side effects that are common and potentially serious. Which drug will work best in an individual is largely a matter of trial and error. Electrical cardioversion can sometimes be combined with drugs to cause reversion to sinus rhythm. It is also not unreasonable in certain circumstances to remain in atrial fibrillation on medications to control the rate and thin the blood.