Can you switch from Effexor to Prozac without weaning of Effexor first?

Yes. I am not a doctor, however, I took Effexor for over 12 years and switched to Prozac because I absolutely hated the side effects of Effexor. I took both medications for two weeks before tapering off the Effexor. Many people that have taken Effexor have very uncomfortable withdrawals, including myself, especially if they have taken it over a long period of time. I desperately wanted off Effexor so My doctor suggested I switch to Prozac and then wean myself off the Prozac. I began by taking Prozac for two weeks while still taking my regular dose of Effexor. After two weeks of taking both Prozac and Effexor, my doctor suggested I reduce the Effexor, taking it only every other day for one week (I was already on the lowest possible mg dose). After that week I cut out the Effexor completely. I took Prozac for another 7-10 days and then stopped the Prozac. I occasionally had very mild withdrawal symptoms, most of which occurred after stopping the Prozac and mostly in the evening, but it was very manageable and lasted only a few days.

If you have a difficult time withdrawing from Effexor I would suggest talking with your doctor about weaning yourself slowing off, by switching to Prozac like I did. I had tried many times, with a doctors assistance, to wean off of Effexor and I could never get past the third or forth day until I added the Prozac.

I changed from Lexapro to Effexor without weaning off first. Lexapro is the same type as Prozac, so I suppose you can. I felt a bit funny for a few days, that was about it.