My doctor put me on Prozac for 10 days, while also taking the Effexor, and then I stopped the Effexor. Next, I was able to come off the Prozac pretty quickly – about two weeks. The Prozac has a long half life, so it remains in your system for a while after you stop taking it. The body slowly rids itself of the Prozac and this has the similar effect of a slow taper. I did experience some minor discontinuation symptoms which resolved themselves over a two week period.