(I thought I'd post this here as well, so it would be easier to "Google", in case someone is looking for answers...)
I expect that PPI's are interchangable. I've had my PPI changed several times and I have not had to wait any time in between the changes. I started with Prilosec, went to Nexium, then started on Protonix, and never had even a day of waiting time in between them. (Mine were switched looking for better results, not side-effects.)
Good luck finding something that works!