I am researching horse tranquilizers for a a paper in class and I can't find if they are deadly to humans?
- Josh

The basic answer is, yes. Tranquilizers are even deadly to horses if they are given an overdose. Some tranquilizers, such as Acepromazine, lower blood pressure and reduce the horse's heart rate. An overdose could be deadly as it could lower blood pressure and heart rates too low. They could be harmful to both horses and humans -- it would just take a larger dose to affect a horse (since their bodies are larger).

The drugs that are actually used to put a horse to sleep are Barbiturates (usually in combination with a sedative to calm the horse first). Barbiturates depress the nervous system, and they will induce sleep and depress respitory functions and muscle control, and in a large enough dose (like those given to put horses down) they induce a coma and death.

Basically, tranquilizers depress body functions, (which makes the animal tanquil), and an overdose can lower heart rate, brain function, blood pressure, or respitory rate too low and kill a horse (or human).

Here is a veterinary site with more information: http://lam.vet.uga.edu/LAM/LM000084.HTML