150 is pretty low for Effexor...rather than stopping you may want to go to 225 or so and see if that helps...the zaps always happen to me if I miss a dose or something like that. In other words, the level gets too low, the zaps start. I'm currently at 225, but I was taking as much as 600 a day before I started lithium, so there's room to work. You definitely need to come down slowly, though. Some docs will even give a weeks worth of Prozac at the end to keep things mellow.

Good luck
DJ