[QUOTE=Ghazzu;8284570]
Acepromazine has no analgesic properties.[/QUOTE]
No, it doesn’t. But it can have a positive effect on horses that have muscle soreness. It stops the spasms and increases blood flow.
https://asci.uvm.edu/equine/law/articles/tying.htm
A mild case of tying up may be treated with a nonsteroidal anti-inflammatory (i.e. Phenylbutazone) and rest for 3-5 days with a gradual increase in exercise. A decrease in training intensity and grain intake will usually be recommended. Sedatives such as Acepromazine which causes sedation and relaxation by depressing the central nervous system, may be given to decrease the anxiety and spasms after the horse ties up. In some chronic cases, Acepromazine may be used in a preventative effort prior to exercise, to help promote vasodilatation or opening of the outlying blood vessels. Veterinarians may give the horses immediate intravenous Thiamin or intramuscular Vitamin E and Selenium injections to aid return to health or monthly prophylactic injections to decrease potential onset of tying up episodes.