Hi -
I tried Effexor when prozac stopped working for PMS. I gained 50 lbs in less than a year - was depressed ALL the time (instead of 2 weeks/month) and when I missed a dose I had very weird brain "zaps."
It felt like an electric jolt zapping around my head when I moved my eyes. I had a very difficult time withdrawing from this drug due to the brain zaps as well as flu-like symptoms - body aches and fatigue.
Experiences are different for everyone, but I would recommend prozac over Effexor (or any of the other antidepressants for that matter!) any day.
Joni