Make sure you get a stash of low dose Zyprexa if you plan to take it PRN. Say, 2.5 or 5 mg, but not more. then you can gradually find the dose you need, and won't be using a pill cutter. As Marshellette explained, no Prozac taken alone for bipolar people - not only can you get too high, but you can also lose your sleep altogether.

I went off Prozac cold turkey without issues, but i was taking 10 mg (lowest dose) and you are taking 5 times that. You probably need to taper off, and not stop Zyprexa until you are completely off Prozac.