I know first hand how you feel. When Fletcher was neutered last August he was given ACE too. I was not aware that it was harmful to the breed until I came on here and begged for help because Fletcher was still having to be physcially lifted and taken outside to potty after a week and he started having arrythmias. When Gmac asked for his list of meds and I told her what he had been given I learned about ACE. I was sick that I had unknowingly subjected my baby to that:( I gave that vet a piece of my mind and then found a new one. I am shocked that your vet being boxer owned didn't know better. So sad.