Flecainide
"I started taking Flecainide Acetate , it  was prescribed for two 100 mg tablets  twice a day.  I took one the first day and no ill affects. Took the second one the next day and during the night had a bad attack of diarrhea for over twenty minutes  in the bathroom. After that it hit again about two hours later the same thing.  I won't do into details about what happen then, but I had a bad problem with it. I never had anything like that in my entire life. will talk to the doctor tomorrow about it , or his nurse. Last time I had a bad reaction from a medicine I told the doctor and she said ( it might of been a virus)  I had viruses all my life including the flu, and none every acted like this one did."