I was on dofetilide and it worked for almost 5 yes w/o incident. would drinking a beer affect the potency of this med and cause it not to work...

Possibly: Drinking a lot of beer causes atrial fibrillation. It's independent of dofetilide. It's called the holiday heart syndrome. See: http://www.Whhs.Com/news?Id=8049 how many beers is safe? Up to 2 a day. (1 for women).

Not necessarily: If you have atrial fibrillation, excessive alcohol intake can precipitate an event. Dofetilide has an additional potential to cause dangerous cardiac rhythms if you use have low potassium/magnesium levels or use certain medications (see qtdrug.Org for meds to avoid).