"i have been taking pristiq for about 8 months. no problems, no side effects, my anxiety was magically gone. i have tried several medications and had side effects to all of them so i was amazed when i had 0 side effects to pristiq. this month my formulary changed and my insurance forced me to change to desvenlafaxine succinate er instead of name brand. a week later i feel like i&#039;m detoxing. dizziness, light headedness, achy muscles and my anxiety keeps creeping up on me. i&#039;m wondering if anyone else has had this problem?"