Pristiq and Effexor are essentially the same medication, so the switch should be relatively easy,
and save you some money, too. I'm not sure I understand the switch, because Pristiq is the new Effexor, so if it isn't for financial reasons, kind of hard to see the point of going through it. Certainly some people have different reactions to them, and so just because Pristiq works also doesn't guarantee Effexor will work, and it might work better, who knows.