Acepromazine? Highly unlikely. Try Benadryl. Your vet can give you a correct doseage based on your cat's weight. It is not the same as dosing for people, so ASK first.

The anti-histamines contol motion sickness because they decrease the impulses sent from the vestibular apparatus(in the ear) to the emetic center in the brain during continuous motion. This won't work if your cat is vomiting from something like a gastroenteritis, where they are receiving a different kind of stimulation to upchuck. The benadryl has a bit of a sedative effect, but nothing like the effects that Ace can have.

Check with your vet.

~Jen