Be careful of the amnesia side effect with Ambien. I've had several weird experiences with it, and now don't take it when I fly. Agree that dramamine makes you sleepy, but also spacy the next day.

What ever you do, don't waste your money on this:
http://www.1stclasssleeper.com/
Looks good, but didn't work for me. I just wrestled with it the whole flght and it feels like your reclined onto a pool airmattress.