(From the previous thread).
This is interesting. Technically speaking, the term "horse tranquilizer" stands for Ketamine. Ketamine is a dissociative anesthetic originally used for humans. I actually had a minor surgery done under it decades ago and can say that it felt like a slightly stronger version of anesthesia one gets for endoscopy. Strange, but not totally unpleasant, feeling with no memory of event. My 3-year old kid, who had a minor surgery under it later, was hallucinating afterwards, also a known effect of the drug.
But because people respond to it differently, it got mixed with cocaine and sold on the streets under the name "special C", or "special K". Then it was banned for humans, and left for animals. Hence, "horse tranquilizer". Now it is used for treatment of depression. I heard of a person who committed suicide when using ketamine recreationally but don't know any details.
In all cases, horses or animals, Ketamine is used IV, or as a shot in the muscle.
https://www.medicalnewstoday.com/articles/3
02663.php
(Interesting stuff about PTSD here).
However, it is very difficult (and illegal) to purchase it without a license and a DEA number.
Online, I found a list of sedating drugs for horses, mostly from what in people would amount to antipsychotic class. I doubt it is legal for a non-vet or a non-MD to purchase it, (but I have heard that people buy lots of things online, it is shocking how some don't care about their health).
These "tranquilizers" may be more dangerous than ketamine as not only sedation but drop of blood pressure might occur. All depends on the dose and person.
Anyhow, use without a license in a dog or a horse would be a criminal case, in humans, it would be way worse.