Serotonin syndrome is extremely rare. On the other hand, Buspar doesn't really work very often -- it doesn't even work in clinical trials. So if you're that scared of it, it isn't likely to be a great answer anyway. I would say the more important question is, if you're still that anxious, Prozac isn't known to be the most effective drug for anxiety as it's a more stimulating ssri. It's the easiest one to stop taking, so a great one to try, but if anxiety is a big problem for you it might be the Prozac just isn't the right med for you. If depression is the big issue and your only fear is medication, that would be one thing, but if you take medication for anxiety and you're on Prozac, I'd talk to your psychiatrist about maybe trying something that works instead of constantly adding on to something that apparently isn't working. Just a thought.