I don't know about panic attacks but I believe Cymbalta has an *extremely* short half-life (meaning it gets eliminated from your system much more quickly than other ADs, so if you stop taking it it hits you all at once).

I took it a few years ago, as did a friend of mine, and when we both missed a few doses we felt like we were seasick within 48 hours.

(It's something to keep in mind, if you ever go off it intentionally for whatever reason, to titrate [i.e. cut your dose in half but keep taking it for like five days, then halve that if you can for a few days, depending on what kind of pill it is, and so on.])