"i have been taking the generic tenormin (atenenol) for probably 32 years now.  25 mg.  i take it at night.  never had a problem, except when i could not see my doctor and had to see someone else in the practice.  he thought i should get off the drug; said there were new better things.  he took me off it and i was going on vacation the next day or so.  worse vacation ever.  i thought i was dying.  my heart was pounding.  i thought i would die up in the mountains.  got back on atenol when i got back home.  everything was normal.  if i accidently miss a day or so, i can tell the difference.  i don&#039;t know about all the side effects other people have had, but it works great for me."