Hi Blonde--Cymbalta is a type of antidepressant, that is used for fibro pain. It is an SSNRI or selective serotonin-norepinephrine re-uptake inhibitor. It block or delays the re-uptake of the neurotransmitters, serotonin and norepinephrine, by the presynaptic nerves. This increases the levels of these two neurotransmitters in the synapse and tends to elevate mood. Research has shown that this drug and amitryptiline help with pain. I can't remember if they know the exact process works (fibro fog) but there's lots of info out there on the web.
Other antidepressants may help but typically as much. I think the issue may be how large a dose can be tolerated without significant side effects. And with fibro, what works for one person may do diddlysquat for another.
Willow is correct, Lyrica treats nerve pain and epilepsy.