Acepromazine is a drug I will never ever give to a dog again.
I agree with Shirley, it seems very fearful. Sadly, that's often a trait you can work to help control, but it is something your dog simply may be born with. You can work on desensitizing to vet... by doing by, let them toss a treat, go home. Do it for quite a while. Ditto on muzzle.. do it at home for a few mins, take off and treat. Work on making both as unstressful as possible. But better to muzzle than have a bite incident.