Hope I can help ya out, I did the switch but I went from fluoxetine to lexapro. I think I was taking 40 mg of prozac and The problem I had with it is I couldn't sleep!!! I would go days without sleep, it made me very wired, it did help the anxiety though but when you don't get sleep you panic more, So I decided after being on the fluoxetine for about 3 months to try lexapro 10mg and I was on that for a good 6 months! I absoultely loved it!!! there were two negatives about lexapro, I did gain about 20 pounds and My sex drive went away. But I had no anxiety and I felt great! I just stopped lex 3 days ago to see how I do without meds for the first time in 1 1/2 years. I am planning to get pregnant so I really don't want drugs in my system but If my panic does come back I can go on lex again.
The switch from prozac to lexapro was fine, No side effects from stopping one and no anxiety. I hope that helped you. prozac is a great drug for lots of people and very safe( I did my research) It is unlikely to cause weight gain and actually I lost weight on it due to you losing your appetite for a while.