I'm not a doc but I do know a bit about this issue... Anti depressants are a lot like birth control pills in that they are all a little bit different, and different pills effect everyone differently. Sometimes you might need to try a few before you find the right one for you, and none of them are sure bets that you will or won't have side effects.

From what I can tell Sarafem and Prozac are really similar. They are both SSRI's- the same active ingredient. I'm not sure if they are really different or if they are just marketed differently, Sarafem for PMDD and Zoloft for depression, but they can both be used to treat it. Also, Sarafem is usually prescribed differently, sometimes patients are instructed only to take it during the last week or two of their cycle. Sometimes they take it the whole month.

My feelings are, if your doc thought it was the right thing to prescribe, trust her and try it out. If you try it for a few weeks and have bad side effects, talk to her about what would be good to switch to. You may have the same problems with Sarafem, or it might be completely different. You'd never know until you tried it.