I'm on 900mg/day Lithium, along with several others, and my doctor had thoughts of putting me on Prozac. Here is just a blurb of info that I found: It appears that while some people are good candidates for a lithium-Prozac combination, others aren't. While several reports have found that Prozac can interfere with lithium, the two drugs used together can help some depressed people who don't respond to either drug alone.
So it really depends. What works for some may not work for others. And, you'll never know unless you try it. Hope this helps a wee bit.