I have a mixed breed Dalmatian and I am taking him to be castrated on Friday.?

I have a mixed breed Dalmatian and I am taking him to be castrated on Friday. However, it is quiet a drive (over an hour) to get to the vet. My dog gets very car sick. The vet has advised that I give him Calmivet 2-3hrs before the drive. Just wondering if this is ok considering he will be operated on the same day