Canine side effects to the sedative Acepromazine?

We have an older dog, Sydney, who has really bad anxiety when it comes to fireworks and gun shot noises. Our vet prescribed Acepromazine, a sedative to make him calm down. The last week he has been acting out and tearing up the house, he actually chewed through some drywall after ripping trim off the corners of the doorways. We've been giving him the medication, but it seems like its not working now. We also tested a muzzle on him to maybe see if we could just leave that on while at work and school, but he had an anxiety attack so bad that his nose started bleeding. What should we do?