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}
New Warning About an Old Drug
Acepromazine (acepromazine maleate, acetylpromazine, ACE, ACP) is commonly used in veterinary medicine as a tranquilizer or pre-anesthetic agent. In 1996, the University of California at Davis issued a memo describing three Boxers suffering adverse reactions to acepromazine (respiratory arrest in one, and severe decreased heart rate in two), and suggesting that the drug be avoided in the Boxer breed. This memo confirmed anecdotal reports which had been circulating for years in various countries; a discussion on the Veterinary Information Network in April of 1996 included long acknowledgment of the breed’s sensitivity by vets in the US, Canada, the UK, Australia, and Greece. Many veterinarians took notice of the UCDavis memo, and veterinary textbooks and publications began to include information on the breed’s sensitivity to, and cautions orr ecommendations for avoidance of, the drug in Boxers. More than a decade later, however, some veterinarians still claim that they have never had a problem with acepromazine in Boxers, and a few insist on using it despite their clients’ requests to avoid it. While it is true that not all Boxers will experience an adverse reaction, that is of little comfort to the owner who requested the drug not be used, gave in to the vet’s insistence that it was safe, and lost their Boxer as a result.
A common argument that vets use to refute the adverse effects of acepromazine in Boxers is that affected dogs must have an underlying heart condition. While this has never been studied, and may or may not be true, it is important to point out that in a breed that is prone to a heart condition which may not be detected except by necropsy, there is simply no way for a vet to know if the dog to which he’s about to administer acepromazine has an underlying heart condition. Given some estimates that 50-80% of the breed is affected with ARVC, a vet who uses this rationale is taking quite a risk when he administers acepromazine to any Boxer. Another justification vets give for acepromazine use in Boxers is that they give a low dose, so the risk is reduced. However, there are reports of Boxers collapsing even after very small doses of acepromazine. Some vets give an anticholinergic drug, such as atropine, in conjunction with acepromazine; this protocol may help prevent the bradycardiac effects of the drug, but there have been anecdotal reports of adverse reactions in the breed even with this addition.
Finally, there are some vets who dismiss concerns about acepromazine and Boxers as “Internet lore.” These vets should be referred to their veterinary drug handbook entry on acepromazine, as most if not all discuss the issues regarding Boxers and acepromazine. While a vet who has not experienced adverse effects with the drug in Boxers may be comfortable with its use, the owner is the primary patient advocate and their wishes should be respected. With the availability of other tranquilizers and preanesthetic drugs which are as effective as acepromazine, a knowledgeable Boxer owner is completely with his/her rights to insist the drug not be used on their dog, especially in light of the continued widespread veterinary caution against the use of the drug in the Boxer breed. {Source - BOSS Boxers}