I don't know the timing of going off the Lexapro and when you had palpitations but a possible side effect is feelings of electric like shocks, especially when going off the medication. It's best to gradually step down from one medication before starting another. There are 3 brain chemicals that an antidepressants will affect, serotonin, dopamine, and norepinephrine. Lexapro and Prozac are SSRIs, they affect serotonin. I don't believe they are the same thing or would have the same side effects. It might not even be the main component of the medication that is causing the flutters. It could be caused an ingredient that the Prozac doesn't have. If you have this issue with every SSRI, then you can still be prescribed a medication that affects one of the other 2 brain chemicals. I currently take Lexapro, an SSRI and Wellbutrin which works on dopamine. You won't know how Prozac will affect you until you try it. Stepping down gradually off the Lexapro and stepping gradually up on the Prozac will lesson the chance of side effects. Hopefully this change will stop the palpitations.