I have never taken Prozac but I can tell you that when the docs were trying to figure out my diagnosis I had an agitation reaction with several different antidepressants and each of those times it took between 2 and 3 weeks and came on suddenly. Typically you wouldn't have anough drug in your system to have a reaction before at least a week (unless it's an allergic reaction like hives or something). Good luck with this process... sorry you're having to go through it twice. Hang in there and post as much as you need.