"Giant breeds, as well as greyhounds, appear quite sensitive to the clinical effects of the drug, yet terrier breeds appear more resistant. Conversely, boxer dogs are predisposed to the hypotensive and bradycardiac effects of the drug." 
 
Handbook of Veterinary Drugs 
Second Edition, 1998 
D.G. Allen, J.K. Pringle, D.A. Smith with K. Pasloske and K. Day 
________________________________________ 
 
"Acepromazine may cause syncope in brachycephalic breeds. Boxers are reportedly very sensitive to the hypotensive and bradycardiac effects of acepromazine and even small doses should be used cautiously in this breed." 
 
Psychopharmacology of Animal Behavior Disorders 
1998 
Nicholas H. Dodman, Louis Schuster 
________________________________________ 
 
"Giant breeds and greyhounds may be extremely sensitive to the drug, while terrier breeds are somewhat resistant to its effects. Boxers are reported to be very sensitive to the hypotensive and bradycardiac effects of acepromazine...." 
 
Veterinary Drug Handbook 
Third Edition, 1999 
Donald C. Plumb 
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"Fainting and cardiovascular collapse has been reported to occur occasionally in all species of animal following the use of even low doses of acepromazine. In some cases it may have been due to administration to a hypovolaemic animal but in others it has not been explained. Some strains of Boxers are known for collapsing after a very small dose of acepromazine given by any route, and it has been suggested that this may be due to orthostatic hypotension or to vasovagal syncope." 
 
Veterinary Anaesthesia 
Tenth Edition, 2001 
L.W. Hall, K.W. Clarke, C.M. Trim 
________________________________________ 
 
"Acepromazine can cause syncope associated with high vagal tone and subsequent bradycardia; this occurs in brachycephalic breeds, particularly in Boxers." 
 
Veterinary Pharmacology & Therapeutics 
Eighth Edition, 2001 
H. Richard Adams 
________________________________________ 
 
"Boxers are known to be unduly susceptible to ACP [acepromazine], and occasionally respond to the drug by collapsing with profound hypotension and bradycardia." 
 
Anaesthesia for Veterinary Nurses 
2003 
Elizabeth Welsh 
________________________________________ 
 
"The side-effects of short term use of acepromazine include the following (Booth, 1988; Dodman,1998): 
Hypotension (often accompanied by a compensatory tachycardia) 
Bradycardia 
Syncope, particularly in brachycephalic breeds, the Boxer being especially sensitive 
Hypothermia" 
 
Currently posted on the website of the South African Veterinary Council 
http://www.savc.co.za/policies.htm 
________________________________________ 
 
"In some dogs, particularly Boxers and other short-nosed breeds, spontaneous fainting or syncope may occur, due to sinoatrial block caused by excessive vagal tone, and an attack may be precipitated by acepromazine" 
 
This is a direct quote from the Novartis product insert, and is currently posted on both of these websites: 
Veterinary Medicines Directorate (UK; government agency of the Department for Environment, Food and Rural Affairs) 
http://www.vmd.gov.uk/espcsite/Documents/140754.DOC 
 
National Office of Animal Health (UK) 
http://tinyurl.com/5syfo7 
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