Dramamine for car sickness?

Okay me and my gf is going to VA which is a 4hr drive for us.Well we cant leave my mini schnauzer home and plus i like taking her on trips.Due to the monition she seem to get car sick a lot,we drove 3.5 hr to the beach a few months back and the whole way she throw up a total of 10+ times.So i talk to my vet and he told me to give her Dramamine 45-1 hr before we leave.So here is the question:I was told to give her 1/2 a pill so if i apply flea med. to her tomorrow(wednesday) then give her dramamine thursday before we leave will it hurt her?do dramamine works?thank you