There are lots of different kinds of anti-depressants. None of them are exactly the same as each other, but they fall into different categories. Prozac is a selective serotonin reuptake inhibitor (SSRI). Cymbalta is a norephrine reuptake inhibitor, which is a VERY similar group, but it acts on adrenaline as well as serotonin, and is therefore stronger and has stronger side effects. I've been on both kinds, and found them both fine, except that the SSRI didn't work for me.