The Boxer Blog...

The Boxer is reported to have a breed-related sensitivity to acepromazine. In 1996 a warning was placed in the cardiology section of the Veterinary Information Network (VIN), a US-based network for practicing veterinarians, entitled "Acepromazine and Boxers." It described several adverse reactions to acepromazine in three Boxers at the University of California at Davis veterinary teaching hospital. The reactions included collapse, respiratory arrest, and profound bradycardia (slow heart rate, less than 60 beats per minute). While there is disagreement among some veterinarians on this point, a number of veterinary publications recommend the drug be avoided in the breed. Individual dogs of any breed can have a profound reaction characterized by hypotension (low blood pressure), especially if there is an underlying heart problem. Acepromazine should be used with caution  {Source - Wikipedia}

This is a re-post that I find very informational. I am a firm believer that people over vaccinate our pets, and this is very educational for those who have questions like I do, and old schoolers out there who believe otherwise.