Before you take your Boxer for surgery, even a routine spay or neuter please read the following.
Acepromazine (acepromazine maleate, acetylpromazine, ACE, ACP, PromAce)
Acepromazine is commonly used as a tranquilizer or pre-anasthetic agent.
Boxers have a breed related sensitivity to ACE, the reactions include collapse, respiratory arrest, and profound bradycardia (slow heart rate, less than 60 beats per minute).
Boxers have died from the use of ACE and there are reports of Boxers collapsing even after very small doses of acepromazine.
Please tell your vet you do not want ACE used on your Boxer and get them to mark on your Boxers chart "NO ACE" where it will be clearly visable - remember YOU are your pets primary advocate and your wishes should be respected. If your vet tries to dismiss you or convince you ACE is safe in Boxers - FIND A NEW VET.
The warnings on the use of ACE in Boxers and can be found in many veterinary drug handbooks, veterinary textbooks, reference books, and veterinary organization websites.
A few links to some information on ACE:
American Boxer Club Acepromazine Warning
WARNING! Acepromazine