we used it for miko when we had to take a 2.5 hour car ride with her (she panics in the car). it knocked her out basically, but not completely. she was still really nervous on city streets. she didn't seem to have any adverse reaction to it. it's used frequently on dogs as pre-anesthetic and for dogs with severe anxiety with travel.
here's a link with more info on 'ace' (acepromazine)
http://www.marvistavet.com/html/body_acepromazine.html
best of luck with your baby
