atrial fibrillation
"After ER episode for atrial fib (which I believe was one-time stress-induced issue) I was bullied into taking this med by hospital upon discharge. My job as a knowledge worker requires me to *think* for a living. I'm considered an expert in my field.
This damn drug put me in a mental fog to the point that I stared at the computer screen wondering what I was looking at.
My mood became aggressive, depressed and I felt increasingly isolated, listless, tired, but hard to sleep.
I gained about 15 lb with no change in diet, in fact I probably ate less. I lost desire for my usual workout routine. 
After weaning off after 6 months, and now taking only daily aspirin, I'm back to my happy self, focussed and motivated.
This is a bad drug, IMO."